Add build script

29 files changed, 3318 insertions, 0 deletions

diff --git a/libbuild2/build/script/lexer+command-line.test.testscript b/libbuild2/build/script/lexer+command-line.test.testscript
new file mode 100644
index 0000000..1777583
--- /dev/null
+++ b/libbuild2/build/script/lexer+command-line.test.testscript
@@ -0,0 +1,152 @@
+# file      : libbuild2/build/script/lexer+command-line.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+test.arguments = command-line
+
+: redirect
+:
+{
+  : pass
+  :
+  $* <"cmd <| 1>|" >>EOO
+  'cmd'
+  <|
+  '1'
+  >|
+  <newline>
+  EOO
+
+  : null
+  :
+  $* <"cmd <- 1>-" >>EOO
+  'cmd'
+  <-
+  '1'
+  >-
+  <newline>
+  EOO
+
+  : trace
+  :
+  $* <"cmd 1>!" >>EOO
+  'cmd'
+  '1'
+  >!
+  <newline>
+  EOO
+
+  : merge
+  :
+  $* <"cmd 1>&2" >>EOO
+  'cmd'
+  '1'
+  >&
+  '2'
+  <newline>
+  EOO
+
+  : str
+  :
+  $* <"cmd <a 1>b" >>EOO
+  'cmd'
+  <
+  'a'
+  '1'
+  >
+  'b'
+  <newline>
+  EOO
+
+  : str-nn
+  :
+  $* <"cmd <:a 1>:b" >>EOO
+  'cmd'
+  <:
+  'a'
+  '1'
+  >:
+  'b'
+  <newline>
+  EOO
+
+  : doc
+  :
+  $* <"cmd <<EOI 1>>EOO" >>EOO
+  'cmd'
+  <<
+  'EOI'
+  '1'
+  >>
+  'EOO'
+  <newline>
+  EOO
+
+  : doc-nn
+  :
+  $* <"cmd <<:EOI 1>>:EOO" >>EOO
+  'cmd'
+  <<:
+  'EOI'
+  '1'
+  >>:
+  'EOO'
+  <newline>
+  EOO
+
+  : file-cmp
+  :
+  $* <"cmd <<<in >>>out 2>>>err" >>EOO
+  'cmd'
+  <<<
+  'in'
+  >>>
+  'out'
+  '2'
+  >>>
+  'err'
+  <newline>
+  EOO
+
+  : file-write
+  :
+  $* <"cmd >=out 2>+err" >>EOO
+  'cmd'
+  >=
+  'out'
+  '2'
+  >+
+  'err'
+  <newline>
+  EOO
+}
+
+: cleanup
+:
+{
+  : always
+  :
+  $* <"cmd &file" >>EOO
+  'cmd'
+  &
+  'file'
+  <newline>
+  EOO
+
+  : maybe
+  :
+  $* <"cmd &?file" >>EOO
+  'cmd'
+  &?
+  'file'
+  <newline>
+  EOO
+
+  : never
+  :
+  $* <"cmd &!file" >>EOO
+  'cmd'
+  &!
+  'file'
+  <newline>
+  EOO
+}
diff --git a/libbuild2/build/script/lexer+first-token.test.testscript b/libbuild2/build/script/lexer+first-token.test.testscript
new file mode 100644
index 0000000..6709e60
--- /dev/null
+++ b/libbuild2/build/script/lexer+first-token.test.testscript
@@ -0,0 +1,30 @@
+# file      : libbuild2/build/script/lexer+first-token.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+# Note: this mode auto-expires after each token.
+#
+test.arguments = first-token
+
+: assign
+:
+$* <"foo=" >>EOO
+'foo'
+'='
+<newline>
+EOO
+
+: append
+:
+$* <"foo+=" >>EOO
+'foo'
+'+='
+<newline>
+EOO
+
+: prepend
+:
+$* <"foo=+" >>EOO
+'foo'
+'=+'
+<newline>
+EOO
diff --git a/libbuild2/build/script/lexer+second-token.test.testscript b/libbuild2/build/script/lexer+second-token.test.testscript
new file mode 100644
index 0000000..d5f3329
--- /dev/null
+++ b/libbuild2/build/script/lexer+second-token.test.testscript
@@ -0,0 +1,53 @@
+# file      : libbuild2/build/script/lexer+second-token.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+# Note: this mode auto-expires after each token.
+#
+test.arguments = second-token
+
+: assign
+:
+$* <"=foo" >>EOO
+=
+'foo'
+<newline>
+EOO
+
+: append
+:
+$* <"+= foo" >>EOO
++=
+'foo'
+<newline>
+EOO
+
+: prepend
+:
+$* <" =+ foo" >>EOO
+=+
+'foo'
+<newline>
+EOO
+
+: assign-leading
+:
+$* <"foo=bar" >>EOO
+'foo=bar'
+<newline>
+EOO
+
+: append-leading
+:
+$* <"foo+= bar" >>EOO
+'foo+='
+'bar'
+<newline>
+EOO
+
+: prepend-leading
+:
+$* <"foo =+bar" >>EOO
+'foo'
+'=+bar'
+<newline>
+EOO
diff --git a/libbuild2/build/script/lexer+variable-line.test.testscript b/libbuild2/build/script/lexer+variable-line.test.testscript
new file mode 100644
index 0000000..e4b5adb
--- /dev/null
+++ b/libbuild2/build/script/lexer+variable-line.test.testscript
@@ -0,0 +1,12 @@
+# file      : libbuild2/build/script/lexer+variable-line.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+test.arguments = variable-line
+
+: basic
+:
+$* <"a 'b c'" >>EOO
+'a'
+'b c'
+<newline>
+EOO
diff --git a/libbuild2/build/script/lexer+variable.test.testscript b/libbuild2/build/script/lexer+variable.test.testscript
new file mode 100644
index 0000000..54b0a30
--- /dev/null
+++ b/libbuild2/build/script/lexer+variable.test.testscript
@@ -0,0 +1,25 @@
+# file      : libbuild2/build/script/lexer+variable.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+# Test handling custom variable names ($*, $~, $NN).
+#
+test.arguments = variable
+
+: primary-target
+:
+{
+  : only
+  :
+  $* <">" >>EOO
+  '>'
+  <newline>
+  EOO
+
+  : followed
+  :
+  $* <">abc" >>EOO
+  '>'
+  'abc'
+  <newline>
+  EOO
+}
diff --git a/libbuild2/build/script/lexer.cxx b/libbuild2/build/script/lexer.cxx
new file mode 100644
index 0000000..1f7e4fc
--- /dev/null
+++ b/libbuild2/build/script/lexer.cxx
@@ -0,0 +1,254 @@
+// file      : libbuild2/build/script/lexer.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/build/script/lexer.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      using type = token_type;
+
+      void lexer::
+      mode (build2::lexer_mode m, char ps, optional<const char*> esc)
+      {
+        bool a (false); // attributes
+
+        const char* s1 (nullptr);
+        const char* s2 (nullptr);
+
+        bool s (true); // space
+        bool n (true); // newline
+        bool q (true); // quotes
+
+        if (!esc)
+        {
+          assert (!state_.empty ());
+          esc = state_.top ().escapes;
+        }
+
+        switch (m)
+        {
+        case lexer_mode::command_line:
+          {
+            s1 = "=!|&<> $(#\t\n";
+            s2 = "==          ";
+            break;
+          }
+        case lexer_mode::first_token:
+          {
+            // First token on the script line. Like command_line but
+            // recognizes variable assignments as separators.
+            //
+            s1 = "=+!|&<> $(#\t\n";
+            s2 = " ==          ";
+            break;
+          }
+        case lexer_mode::second_token:
+          {
+            // Second token on the script line. Like command_line but
+            // recognizes leading variable assignments.
+            //
+            // Note that to recognize only leading assignments we shouldn't
+            // add them to the separator strings (so this is identical to
+            // command_line).
+            //
+            s1 = "=!|&<> $(#\t\n";
+            s2 = "==          ";
+            break;
+          }
+        case lexer_mode::variable_line:
+          {
+            // Like value except we don't recognize '{'.
+            //
+            s1 = " $(#\t\n";
+            s2 = "      ";
+            break;
+          }
+        default:
+          {
+            base_lexer::mode (m, ps, esc);
+            return;
+          }
+        }
+
+        assert (ps == '\0');
+        state_.push (state {m, a, ps, s, n, q, *esc, s1, s2});
+      }
+
+      token lexer::
+      next ()
+      {
+        token r;
+
+        switch (state_.top ().mode)
+        {
+        case lexer_mode::command_line:
+        case lexer_mode::first_token:
+        case lexer_mode::second_token:
+        case lexer_mode::variable_line:
+          r = next_line ();
+          break;
+        default: return base_lexer::next ();
+        }
+
+        if (r.qtype != quote_type::unquoted)
+          ++quoted_;
+
+        return r;
+      }
+
+      token lexer::
+      next_line ()
+      {
+        bool sep (skip_spaces ());
+
+        xchar c (get ());
+        uint64_t ln (c.line), cn (c.column);
+
+        state st (state_.top ()); // Make copy (see first/second_token).
+        lexer_mode m (st.mode);
+
+        auto make_token = [&sep, ln, cn] (type t)
+        {
+          return token (t, sep, ln, cn, token_printer);
+        };
+
+        // Handle attributes (do it first to make sure the flag is cleared
+        // regardless of what we return).
+        //
+        if (st.attributes)
+        {
+          assert (m == lexer_mode::variable_line);
+
+          state_.top ().attributes = false;
+
+          if (c == '[')
+            return make_token (type::lsbrace);
+        }
+
+        if (eos (c))
+          return make_token (type::eos);
+
+        // Expire certain modes at the end of the token. Do it early in case
+        // we push any new mode (e.g., double quote).
+        //
+        if (m == lexer_mode::first_token || m == lexer_mode::second_token)
+          state_.pop ();
+
+        // NOTE: remember to update mode() if adding new special characters.
+
+        switch (c)
+        {
+        case '\n':
+          {
+            // Expire variable value mode at the end of the line.
+            //
+            if (m == lexer_mode::variable_line)
+              state_.pop ();
+
+            sep = true; // Treat newline as always separated.
+            return make_token (type::newline);
+          }
+
+          // Variable expansion, function call, and evaluation context.
+          //
+        case '$': return make_token (type::dollar);
+        case '(': return make_token (type::lparen);
+        }
+
+        // Command line operator/separators.
+        //
+        if (m == lexer_mode::command_line ||
+            m == lexer_mode::first_token  ||
+            m == lexer_mode::second_token)
+        {
+          switch (c)
+          {
+            // Comparison (==, !=).
+            //
+          case '=':
+          case '!':
+            {
+              if (peek () == '=')
+              {
+                get ();
+                return make_token (c == '=' ? type::equal : type::not_equal);
+              }
+            }
+          }
+        }
+
+        // Command operators.
+        //
+        if (m == lexer_mode::command_line ||
+            m == lexer_mode::first_token  ||
+            m == lexer_mode::second_token)
+        {
+          if (optional<token> t = next_cmd_op (c, sep, m))
+            return move (*t);
+        }
+
+        // Variable assignment (=, +=, =+).
+        //
+        if (m == lexer_mode::second_token)
+        {
+          switch (c)
+          {
+          case '=':
+            {
+              if (peek () == '+')
+              {
+                get ();
+                return make_token (type::prepend);
+              }
+              else
+                return make_token (type::assign);
+            }
+          case '+':
+            {
+              if (peek () == '=')
+              {
+                get ();
+                return make_token (type::append);
+              }
+            }
+          }
+        }
+
+        // Otherwise it is a word.
+        //
+        unget (c);
+        return word (st, sep);
+      }
+
+      token lexer::
+      word (state st, bool sep)
+      {
+        lexer_mode m (st.mode);
+
+        // Customized implementation that handles special variable names ($>).
+        //
+        if (m != lexer_mode::variable)
+          return base_lexer::word (st, sep);
+
+        xchar c (peek ());
+
+        if (c != '>')
+          return base_lexer::word (st, sep);
+
+        get ();
+
+        state_.pop (); // Expire the variable mode.
+        return token (string (1, c),
+                      sep,
+                      quote_type::unquoted, false,
+                      c.line, c.column);
+      }
+    }
+  }
+}
diff --git a/libbuild2/build/script/lexer.hxx b/libbuild2/build/script/lexer.hxx
new file mode 100644
index 0000000..cb1f5bf
--- /dev/null
+++ b/libbuild2/build/script/lexer.hxx
@@ -0,0 +1,75 @@
+// file      : libbuild2/build/script/lexer.hxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_BUILD_SCRIPT_LEXER_HXX
+#define LIBBUILD2_BUILD_SCRIPT_LEXER_HXX
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/script/lexer.hxx>
+
+#include <libbuild2/build/script/token.hxx>
+
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      struct lexer_mode: build2::script::lexer_mode
+      {
+        using base_type = build2::script::lexer_mode;
+
+        enum
+        {
+          command_line = base_type::value_next,
+          first_token,  // Expires at the end of the token.
+          second_token, // Expires at the end of the token.
+          variable_line // Expires at the end of the line.
+        };
+
+        lexer_mode () = default;
+        lexer_mode (value_type v): base_type (v) {}
+        lexer_mode (build2::lexer_mode v): base_type (v) {}
+      };
+
+      class lexer: public build2::script::lexer
+      {
+      public:
+        using base_lexer = build2::script::lexer;
+
+        // Note that neither the name nor escape arguments are copied.
+        //
+        lexer (istream& is,
+               const path_name& name,
+               uint64_t line,         // Start line in the stream.
+               lexer_mode m,
+               const char* escapes = nullptr)
+            : base_lexer (is, name, line,
+                          nullptr /* escapes */,
+                          false   /* set_mode */)
+        {
+          mode (m, '\0', escapes);
+        }
+
+        virtual void
+        mode (build2::lexer_mode,
+              char = '\0',
+              optional<const char*> = nullopt) override;
+
+        virtual token
+        next () override;
+
+      private:
+        token
+        next_line ();
+
+        virtual token
+        word (state, bool) override;
+      };
+    }
+  }
+}
+
+#endif // LIBBUILD2_BUILD_SCRIPT_LEXER_HXX
diff --git a/libbuild2/build/script/lexer.test.cxx b/libbuild2/build/script/lexer.test.cxx
new file mode 100644
index 0000000..15c0954
--- /dev/null
+++ b/libbuild2/build/script/lexer.test.cxx
@@ -0,0 +1,77 @@
+// file      : libbuild2/build/script/lexer.test.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#include <cassert>
+#include <iostream>
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/build/script/token.hxx>
+#include <libbuild2/build/script/lexer.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      // Usage: argv[0] <lexer-mode>
+      //
+      int
+      main (int argc, char* argv[])
+      {
+        lexer_mode m;
+        {
+          assert (argc == 2);
+          string s (argv[1]);
+
+          if      (s == "command-line")      m = lexer_mode::command_line;
+          else if (s == "first-token")       m = lexer_mode::first_token;
+          else if (s == "second-token")      m = lexer_mode::second_token;
+          else if (s == "variable-line")     m = lexer_mode::variable_line;
+          else if (s == "variable")          m = lexer_mode::variable;
+          else                               assert (false);
+        }
+
+        try
+        {
+          cin.exceptions (istream::failbit | istream::badbit);
+
+          // Some modes auto-expire so we need something underneath.
+          //
+          bool u (m != lexer_mode::command_line);
+
+          path_name in ("<stdin>");
+          lexer l (cin, in, 1 /* line */, lexer_mode::command_line);
+          if (u)
+            l.mode (m);
+
+          // No use printing eos since we will either get it or loop forever.
+          //
+          for (token t (l.next ()); t.type != token_type::eos; t = l.next ())
+          {
+            // Print each token on a separate line without quoting operators.
+            //
+            t.printer (cout, t, false);
+            cout << endl;
+          }
+        }
+        catch (const failed&)
+        {
+          return 1;
+        }
+
+        return 0;
+      }
+    }
+  }
+}
+
+int
+main (int argc, char* argv[])
+{
+  return build2::build::script::main (argc, argv);
+}
diff --git a/libbuild2/build/script/parser+cleanup.test.testscript b/libbuild2/build/script/parser+cleanup.test.testscript
new file mode 100644
index 0000000..9a5af3d
--- /dev/null
+++ b/libbuild2/build/script/parser+cleanup.test.testscript
@@ -0,0 +1,57 @@
+# file      : libbuild2/build/script/parser+cleanup.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+: always
+:
+$* <<EOI >>EOO
+cmd &file
+EOI
+cmd &file
+EOO
+
+: maybe
+:
+$* <<EOI >>EOO
+cmd &?file
+EOI
+cmd &?file
+EOO
+
+: never
+:
+$* <<EOI >>EOO
+cmd &!file
+EOI
+cmd &!file
+EOO
+
+: empty
+:
+$* <<EOI 2>>EOE != 0
+cmd &""
+EOI
+buildfile:11:6: error: empty cleanup path
+EOE
+
+: missed-before
+:
+{
+  : token
+  :
+  : Path missed before command next token
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd & >file
+  EOI
+  buildfile:11:7: error: missing cleanup path
+  EOE
+
+  : end
+  : Test path missed before end of command
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd &
+  EOI
+  buildfile:11:6: error: missing cleanup path
+  EOE
+}
diff --git a/libbuild2/build/script/parser+command-if.test.testscript b/libbuild2/build/script/parser+command-if.test.testscript
new file mode 100644
index 0000000..a18a885
--- /dev/null
+++ b/libbuild2/build/script/parser+command-if.test.testscript
@@ -0,0 +1,395 @@
+# file      : libbuild2/build/script/parser+command-if.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+: if
+:
+{
+  : true
+  :
+  $* <<EOI >>EOO
+  if true foo
+    cmd1
+    cmd2
+  end
+  EOI
+  ? true foo
+  cmd1
+  cmd2
+  EOO
+
+  : false
+  :
+  $* <<EOI >>EOO
+  if false foo
+    cmd1
+    cmd2
+  end
+  EOI
+  ? false foo
+  EOO
+
+  : not-true
+  :
+  $* <<EOI >>EOO
+  if! true foo
+    cmd1
+    cmd2
+  end
+  EOI
+  ? true foo
+  EOO
+
+  : not-false
+  :
+  $* <<EOI >>EOO
+  if! false foo
+    cmd1
+    cmd2
+  end
+  EOI
+  ? false foo
+  cmd1
+  cmd2
+  EOO
+
+  : without-command
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+    cmd
+  end
+  EOI
+  buildfile:11:3: error: missing program
+  EOE
+}
+
+: elif
+:
+{
+  : true
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    cmd2
+  elif true
+    cmd3
+    cmd4
+  end
+  EOI
+  ? false
+  ? true
+  cmd3
+  cmd4
+  EOO
+
+  : false
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    cmd2
+  elif false
+    cmd3
+    cmd4
+  end
+  EOI
+  ? false
+  ? false
+  EOO
+
+  : not-true
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    cmd2
+  elif! true
+    cmd3
+    cmd4
+  end
+  EOI
+  ? false
+  ? true
+  EOO
+
+  : not-false
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    cmd2
+  elif! false
+    cmd3
+    cmd4
+  end
+  EOI
+  ? false
+  ? false
+  cmd3
+  cmd4
+  EOO
+
+  : without-if
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  elif true
+    cmd
+  end
+  EOI
+  buildfile:12:1: error: 'elif' without preceding 'if'
+  EOE
+
+  : not-without-if
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  elif! true
+    cmd
+  end
+  EOI
+  buildfile:12:1: error: 'elif!' without preceding 'if'
+  EOE
+
+  : after-else
+  :
+  $* <<EOI 2>>EOE != 0
+  if false
+    cmd
+  else
+    cmd
+  elif true
+    cmd
+  end
+  EOI
+  buildfile:15:1: error: 'elif' after 'else'
+  EOE
+}
+
+: else
+:
+{
+  : true
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    cmd2
+  else
+    cmd3
+    cmd4
+  end
+  EOI
+  ? false
+  cmd3
+  cmd4
+  EOO
+
+  : false
+  :
+  $* <<EOI >>EOO
+  if true
+    cmd1
+    cmd2
+  else
+    cmd3
+    cmd4
+  end
+  EOI
+  ? true
+  cmd1
+  cmd2
+  EOO
+
+  : chain
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd
+    cmd
+  elif false
+    cmd
+    cmd
+  elif false
+    cmd
+    cmd
+  elif true
+    cmd1
+    cmd2
+  elif false
+    cmd
+    cmd
+  else
+    cmd
+    cmd
+  end
+  EOI
+  ? false
+  ? false
+  ? false
+  ? true
+  cmd1
+  cmd2
+  EOO
+
+  : command-after
+  :
+  $* <<EOI 2>>EOE != 0
+  if true
+    cmd
+  else cmd
+    cmd
+  end
+  EOI
+  buildfile:13:6: error: expected newline instead of 'cmd'
+  EOE
+
+  : without-if
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  else
+    cmd
+  end
+  EOI
+  buildfile:12:1: error: 'else' without preceding 'if'
+  EOE
+
+  : after-else
+  :
+  $* <<EOI 2>>EOE != 0
+  if false
+    cmd
+  else
+    cmd
+  else
+    cmd
+  end
+  EOI
+  buildfile:15:1: error: 'else' after 'else'
+  EOE
+}
+
+: end
+{
+  : without-if
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  end
+  EOI
+  buildfile:12:1: error: 'end' without preceding 'if'
+  EOE
+
+  : before
+  {
+    : command
+    :
+    $* <<EOI 2>>EOE != 0
+    if true
+      cmd
+    end cmd
+    EOI
+    buildfile:13:5: error: expected newline instead of 'cmd'
+    EOE
+  }
+}
+
+: nested
+:
+{
+  : take
+  :
+  $* <<EOI >>EOO
+  if true
+    cmd1
+    if false
+      cmd
+    elif false
+      if true
+        cmd
+      end
+    else
+      cmd2
+    end
+    cmd3
+  end
+  EOI
+  ? true
+  cmd1
+  ? false
+  ? false
+  cmd2
+  cmd3
+  EOO
+
+  : skip
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    if false
+      cmd
+    elif false
+      if true
+        cmd
+      end
+    else
+      cmd2
+    end
+    cmd3
+  else
+    cmd
+  end
+  EOI
+  ? false
+  cmd
+  EOO
+}
+
+: contained
+:
+{
+  : eos
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+  EOI
+  buildfile:12:1: error: expected closing 'end'
+  EOE
+}
+
+: line-index
+:
+$* -l <<EOI >>EOO
+if false
+  cmd
+  if true
+    cmd
+  end
+  cmd
+elif false
+  cmd
+else
+  cmd
+end
+EOI
+? false # 1
+? false # 6
+cmd # 8
+EOO
+
+: var
+:
+$* <<EOI >>EOO
+if true
+  x = foo
+else
+  x = bar
+end
+cmd $x
+EOI
+? true
+cmd foo
+EOO
diff --git a/libbuild2/build/script/parser+command-re-parse.test.testscript b/libbuild2/build/script/parser+command-re-parse.test.testscript
new file mode 100644
index 0000000..a59b49c
--- /dev/null
+++ b/libbuild2/build/script/parser+command-re-parse.test.testscript
@@ -0,0 +1,11 @@
+# file      : libbuild2/build/script/parser+command-re-parse.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+: double-quote
+:
+$* <<EOI >>EOO
+x = cmd \">-\" "'<-'"
+$x
+EOI
+cmd '>-' '<-'
+EOO
diff --git a/libbuild2/build/script/parser+exit.test.testscript b/libbuild2/build/script/parser+exit.test.testscript
new file mode 100644
index 0000000..53ee1b9
--- /dev/null
+++ b/libbuild2/build/script/parser+exit.test.testscript
@@ -0,0 +1,26 @@
+# file      : libbuild2/build/script/parser+exit.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+: eq
+:
+$* <<EOI >>EOO
+cmd == 1
+EOI
+cmd == 1
+EOO
+
+: ne
+:
+$* <<EOI >>EOO
+cmd!=1
+EOI
+cmd != 1
+EOO
+
+: end
+:
+$* <<EOI 2>>EOE != 0
+cmd != 1 <"foo"
+EOI
+buildfile:11:10: error: expected newline instead of '<'
+EOE
diff --git a/libbuild2/build/script/parser+expansion.test.testscript b/libbuild2/build/script/parser+expansion.test.testscript
new file mode 100644
index 0000000..9f1e774
--- /dev/null
+++ b/libbuild2/build/script/parser+expansion.test.testscript
@@ -0,0 +1,35 @@
+# file      : libbuild2/build/script/parser+expansion.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+: quote
+:
+: Make sure everything expanded as strings.
+:
+$* <<EOI >>EOO
+x = dir/ proj% proj%name proj%proj%dir/type{name   name   {name}}
+cmd dir/ proj% proj%name proj%proj%dir/type{name   name   {name}}
+cmd $x
+EOI
+cmd dir/ proj% proj%name proj%proj%dir/type{name name {name}}
+cmd dir/ proj% proj%name proj%proj%dir/type{name name {name}}
+EOO
+
+: unterm-quoted-seq
+:
+$* <<EOI 2>>EOE != 0
+x = "'a bc"
+cmd xy$x
+EOI
+<string>:1:8: error: unterminated single-quoted sequence
+  buildfile:12:5: info: while parsing string 'xy'a bc'
+EOE
+
+: invalid-redirect
+:
+$* <<EOI 2>>EOE != 0
+x = "1>&a"
+cmd $x
+EOI
+<string>:1:4: error: stdout merge redirect file descriptor must be 2
+  buildfile:12:5: info: while parsing string '1>&a'
+EOE
diff --git a/libbuild2/build/script/parser+here-document.test.testscript b/libbuild2/build/script/parser+here-document.test.testscript
new file mode 100644
index 0000000..8ea6373
--- /dev/null
+++ b/libbuild2/build/script/parser+here-document.test.testscript
@@ -0,0 +1,212 @@
+# file      : libbuild2/build/script/parser+here-document.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+: end-marker
+:
+{
+  : missing-newline
+  :
+  $* <'cmd <<' 2>>EOE != 0
+  buildfile:11:7: error: expected here-document end marker
+  EOE
+
+  : missing-exit
+  :
+  $* <'cmd << != 0' 2>>EOE != 0
+  buildfile:11:8: error: expected here-document end marker
+  EOE
+
+  : missing-empty
+  :
+  $* <'cmd <<""' 2>>EOE != 0
+  buildfile:11:7: error: expected here-document end marker
+  EOE
+
+  : unseparated-expansion
+  :
+  $* <'cmd <<FOO$foo' 2>>EOE != 0
+  buildfile:11:10: error: here-document end marker must be literal
+  EOE
+
+  : quoted-single-partial
+  :
+  $* <"cmd <<F'O'O" 2>>EOE != 0
+  buildfile:11:7: error: partially-quoted here-document end marker
+  EOE
+
+  : quoted-double-partial
+  :
+  $* <'cmd <<"FO"O' 2>>EOE != 0
+  buildfile:11:7: error: partially-quoted here-document end marker
+  EOE
+
+  : quoted-mixed
+  :
+  $* <"cmd <<\"FO\"'O'" 2>>EOE != 0
+  buildfile:11:7: error: partially-quoted here-document end marker
+  EOE
+
+  : unseparated
+  :
+  $* <<EOI >>EOO
+  cmd <<EOF!=0
+  foo
+  EOF
+  EOI
+  cmd <<EOF != 0
+  foo
+  EOF
+  EOO
+
+  : quoted-single
+  :
+  $* <<EOI >>EOO
+  cmd <<'EOF'
+  foo
+  EOF
+  EOI
+  cmd <<EOF
+  foo
+  EOF
+  EOO
+
+  : quoted-double
+  :
+  $* <<EOI >>EOO
+  cmd <<"EOF"
+  foo
+  EOF
+  EOI
+  cmd <<EOF
+  foo
+  EOF
+  EOO
+}
+
+: indent
+:
+{
+  : basic
+  :
+  $* <<EOI >>EOO
+  cmd <<EOF
+    foo
+     bar
+         baz
+    EOF
+  EOI
+  cmd <<EOF
+  foo
+   bar
+       baz
+  EOF
+  EOO
+
+  : blank
+  :
+  $* <<EOI >>EOO
+  cmd <<EOF
+    foo
+
+
+    bar
+    EOF
+  EOI
+  cmd <<EOF
+  foo
+
+
+  bar
+  EOF
+  EOO
+
+  : non-ws-prefix
+  :
+  $* <<EOI >>EOO
+  cmd <<EOF
+   x EOF
+  EOF
+  EOI
+  cmd <<EOF
+   x EOF
+  EOF
+  EOO
+
+  : whole-token
+  : Test the case where the indentation is a whole token
+  :
+  $* <<EOI >>EOO
+  x = foo bar
+  cmd <<"EOF"
+    $x
+    EOF
+  EOI
+  cmd <<EOF
+  foo bar
+  EOF
+  EOO
+
+  : long-line
+  : Test the case where the line contains multiple tokens
+  :
+  $* <<EOI >>EOO
+  x = foo
+  cmd <<"EOF"
+     $x bar $x
+    EOF
+  EOI
+  cmd <<EOF
+   foo bar foo
+  EOF
+  EOO
+
+  : unindented
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd <<EOF
+   bar
+    EOF
+  EOI
+  buildfile:12:1: error: unindented here-document line
+  EOE
+}
+
+: blank
+:
+$* <<EOI >>EOO
+cmd <<EOF
+
+foo
+
+bar
+
+EOF
+EOI
+cmd <<EOF
+
+foo
+
+bar
+
+EOF
+EOO
+
+: quote
+:
+: Note: they are still recognized in eval contexts.
+:
+$* <<EOI >>EOO
+cmd <<"EOF"
+'single'
+"double"
+b'o't"h"
+('single' "double")
+EOF
+EOI
+cmd <<EOF
+'single'
+"double"
+b'o't"h"
+single double
+EOF
+EOO
diff --git a/libbuild2/build/script/parser+here-string.test.testscript b/libbuild2/build/script/parser+here-string.test.testscript
new file mode 100644
index 0000000..8ca1499
--- /dev/null
+++ b/libbuild2/build/script/parser+here-string.test.testscript
@@ -0,0 +1,18 @@
+# file      : libbuild2/build/script/parser+here-string.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+: empty
+:
+$* <<EOI >>EOO
+cmd <""
+EOI
+cmd <''
+EOO
+
+: empty-nn
+:
+$* <<EOI >>EOO
+cmd <:""
+EOI
+cmd <:''
+EOO
diff --git a/libbuild2/build/script/parser+pipe-expr.test.testscript b/libbuild2/build/script/parser+pipe-expr.test.testscript
new file mode 100644
index 0000000..3dd6b1b
--- /dev/null
+++ b/libbuild2/build/script/parser+pipe-expr.test.testscript
@@ -0,0 +1,132 @@
+# file      : libbuild2/build/script/parser+pipe-expr.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+: pipe
+:
+$* <<EOI >>EOO
+cmd1 | cmd2|cmd3
+EOI
+cmd1 | cmd2 | cmd3
+EOO
+
+: log
+:
+$* <<EOI >>EOO
+cmd1 || cmd2&&cmd3
+EOI
+cmd1 || cmd2 && cmd3
+EOO
+
+: pipe-log
+:
+$* <<EOI >>EOO
+cmd1 | cmd2 && cmd3 | cmd4
+EOI
+cmd1 | cmd2 && cmd3 | cmd4
+EOO
+
+: exit
+:
+$* <<EOI >>EOO
+cmd1|cmd2==1&&cmd3!=0|cmd4
+EOI
+cmd1 | cmd2 == 1 && cmd3 != 0 | cmd4
+EOO
+
+: here-doc
+:
+$* <<EOI >>EOO
+cmd1 <<EOI1 | cmd2 >>EOO2 && cmd3 <<EOI3 2>&1 | cmd4 2>>EOE4 >>EOO4
+input
+one
+EOI1
+ouput
+two
+EOO2
+input
+three
+EOI3
+error
+four
+EOE4
+output
+four
+EOO4
+EOI
+cmd1 <<EOI1 | cmd2 >>EOO2 && cmd3 <<EOI3 2>&1 | cmd4 >>EOO4 2>>EOE4
+input
+one
+EOI1
+ouput
+two
+EOO2
+input
+three
+EOI3
+output
+four
+EOO4
+error
+four
+EOE4
+EOO
+
+: leading
+:
+$* <<EOI 2>>EOE != 0
+| cmd
+EOI
+buildfile:11:1: error: missing program
+EOE
+
+: trailing
+:
+$* <<EOI 2>>EOE != 0
+cmd &&
+EOI
+buildfile:11:7: error: missing program
+EOE
+
+: redirected
+:
+{
+  : input
+  :
+  {
+    : first
+    :
+    $* <<EOI >>EOO
+    cmd1 <foo | cmd2
+    EOI
+    cmd1 <foo | cmd2
+    EOO
+
+    : non-first
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd1 | cmd2 <foo
+    EOI
+    buildfile:11:13: error: stdin is both piped and redirected
+    EOE
+  }
+
+  : output
+  :
+  {
+    : last
+    :
+    $* <<EOI >>EOO
+    cmd1 | cmd2 >foo
+    EOI
+    cmd1 | cmd2 >foo
+    EOO
+
+    : non-last
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd1 >foo | cmd2
+    EOI
+    buildfile:11:11: error: stdout is both redirected and piped
+    EOE
+  }
+}
diff --git a/libbuild2/build/script/parser+pre-parse.test.testscript b/libbuild2/build/script/parser+pre-parse.test.testscript
new file mode 100644
index 0000000..4aff3e8
--- /dev/null
+++ b/libbuild2/build/script/parser+pre-parse.test.testscript
@@ -0,0 +1,22 @@
+# file      : libbuild2/build/script/parser+pre-parse.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+: attribute
+:
+{
+  : name
+  :
+  $* <<EOI 2>>EOE != 0
+  x = [foo]
+  EOI
+  buildfile:11:5: error: unknown value attribute foo
+  EOE
+
+  : name-value
+  :
+  $* <<EOI 2>>EOE != 0
+  x = [foo=bar]
+  EOI
+  buildfile:11:5: error: unknown value attribute foo=bar
+  EOE
+}
diff --git a/libbuild2/build/script/parser+redirect.test.testscript b/libbuild2/build/script/parser+redirect.test.testscript
new file mode 100644
index 0000000..641381e
--- /dev/null
+++ b/libbuild2/build/script/parser+redirect.test.testscript
@@ -0,0 +1,441 @@
+# file      : libbuild2/build/script/parser+redirect.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+# @@ Add tests for redirects other than trace, here-*, file and merge.
+# @@ Does it make sense to split into separate files - one per redirect type?
+#
+
+: trace
+:
+{
+  $* <'cmd >!'  >'cmd >!'  : out
+  $* <'cmd 2>!' >'cmd 2>!' : err
+}
+
+: str
+:
+{
+  : literal
+  :
+  {
+    : portable-path
+    :
+    $* <<EOI >>EOO
+    cmd </foo >/bar 2>/baz
+    EOI
+    cmd </foo >/bar 2>/baz
+    EOO
+  }
+
+  : regex
+  :
+  {
+    : portable-path
+    :
+    $* <<EOI >>EOO
+    cmd >/~%foo% 2>/~%bar%
+    EOI
+    cmd >/~%foo% 2>/~%bar%
+    EOO
+  }
+}
+
+: doc
+:
+{
+  : literal
+  :
+  {
+    : portable-path
+    :
+    $* <<EOI >>EOO
+    cmd <</EOI_ >/EOO_ 2>/EOE_
+    foo
+    EOI_
+    bar
+    EOO_
+    baz
+    EOE_
+    EOI
+    cmd <</EOI_ >/EOO_ 2>/EOE_
+    foo
+    EOI_
+    bar
+    EOO_
+    baz
+    EOE_
+    EOO
+
+    : sharing
+    :
+    {
+      : in-out
+      :
+      $* <<EOI >>EOO
+      cmd <<:/EOF >>:/EOF
+      foo
+      EOF
+      EOI
+      cmd <<:/EOF >>:/EOF
+      foo
+      EOF
+      EOO
+
+      : different
+      :
+      {
+        : modifiers
+        :
+        $* <<EOI 2>>EOE != 0
+        cmd <<:/EOF >>:EOF
+        foo
+        EOF
+        EOI
+        buildfile:11:16: error: different modifiers for shared here-document 'EOF'
+        EOE
+
+        : quoting
+        :
+        $* <<EOI 2>>EOE != 0
+        cmd <<EOF >>"EOF"
+        foo
+        EOF
+        EOI
+        buildfile:11:13: error: different quoting for shared here-document 'EOF'
+        EOE
+      }
+    }
+  }
+
+  : regex
+  :
+  {
+    : portable-path
+    :
+    $* <<EOI >>EOO
+    cmd >/~%EOF% 2>/~%EOE%
+    foo
+    EOF
+    bar
+    EOE
+    EOI
+    cmd >/~%EOF% 2>/~%EOE%
+    foo
+    EOF
+    bar
+    EOE
+    EOO
+
+    : sharing
+    :
+    {
+      : in-out
+      :
+      $* <<EOI >>EOO
+      cmd >>~/EOF/ 2>>~/EOF/
+      foo
+      EOF
+      EOI
+      cmd >>~/EOF/ 2>>~/EOF/
+      foo
+      EOF
+      EOO
+
+      : different
+      :
+      {
+        : introducers
+        :
+        $* <<EOI 2>>EOE != 0
+        cmd >>~/EOF/ 2>>~%EOF%
+        foo
+        EOF
+        EOI
+        buildfile:11:18: error: different introducers for shared here-document regex 'EOF'
+        EOE
+
+        : flags
+        :
+        $* <<EOI 2>>EOE != 0
+        cmd >>~/EOF/ 2>>~/EOF/i
+        foo
+        EOF
+        EOI
+        buildfile:11:18: error: different global flags for shared here-document regex 'EOF'
+        EOE
+      }
+    }
+  }
+
+  : overriding
+  :
+  {
+    : literal
+    :
+    {
+      : with
+      :
+      {
+        : string
+        :
+        $* <<EOI >>EOO
+        cmd >>EOF >bar
+        foo
+        EOF
+        EOI
+        cmd >bar
+        EOO
+
+        : regex
+        :
+        $* <<EOI >>EOO
+        cmd >>FOO >>~/BAR/
+        foo
+        FOO
+        bar
+        BAR
+        EOI
+        cmd >>~/BAR/
+        bar
+        BAR
+        EOO
+
+        : self
+        :
+        $* <<EOI >>EOO
+        cmd >>EOF >>EOF
+        foo
+        EOF
+        EOI
+        cmd >>EOF
+        foo
+        EOF
+        EOO
+
+        : different-modifiers
+        :
+        $* <<EOI 2>>EOE != 0
+        cmd >>EOF >>/EOF
+        foo
+        EOF
+        EOI
+        buildfile:11:14: error: different modifiers for shared here-document 'EOF'
+        EOE
+      }
+    }
+
+    : shared
+    :
+    {
+      : after-sharing
+      :
+      $* <<EOI >>EOO
+      cmd >>EOF 2>>EOF >bar
+      foo
+      EOF
+      EOI
+      cmd >bar 2>>EOF
+      foo
+      EOF
+      EOO
+
+      : before-sharing
+      :
+      $* <<EOI >>EOO
+      cmd >>EOF >bar 2>>EOF
+      foo
+      EOF
+      EOI
+      cmd >bar 2>>EOF
+      foo
+      EOF
+      EOO
+    }
+  }
+}
+
+: file
+:
+{
+  : cmp
+  :
+  $* <<EOI >>EOO
+  cmd 0<<<a 1>>>b 2>>>c
+  EOI
+  cmd <<<a >>>b 2>>>c
+  EOO
+
+  : write
+  :
+  $* <<EOI >>EOO
+  cmd 1>=b 2>+c
+  EOI
+  cmd >=b 2>+c
+  EOO
+
+  : quote
+  :
+  $* <<EOI >>EOO
+  cmd 0<<<"a f" 1>="b f" 2>+"c f"
+  EOI
+  cmd <<<'a f' >='b f' 2>+'c f'
+  EOO
+
+  : in
+  :
+  {
+    : missed
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd <<<
+    EOI
+    buildfile:11:8: error: missing stdin file
+    EOE
+
+    : empty
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd <<<""
+    EOI
+    buildfile:11:8: error: empty stdin redirect path
+    EOE
+  }
+
+  : out
+  :
+  {
+    : missed
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd >=
+    EOI
+    buildfile:11:7: error: missing stdout file
+    EOE
+
+    : empty
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd >=""
+    EOI
+    buildfile:11:7: error: empty stdout redirect path
+    EOE
+  }
+
+  : err
+  :
+  {
+    : missed
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd 2>=
+    EOI
+    buildfile:11:8: error: missing stderr file
+    EOE
+
+    : empty
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd 2>=""
+    EOI
+    buildfile:11:8: error: empty stderr redirect path
+    EOE
+  }
+}
+
+: merge
+{
+  : out
+  :
+  {
+    : err
+    :
+    $* <<EOI >>EOO
+    cmd 1>&2
+    EOI
+    cmd >&2
+    EOO
+
+    : no-mutual
+    :
+    $* <<EOI >>EOO
+    cmd 1>&2 2>&1 2>a
+    EOI
+    cmd >&2 2>a
+    EOO
+
+    : not-descriptor
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 1>&a
+    EOI
+    buildfile:11:8: error: stdout merge redirect file descriptor must be 2
+    EOE
+
+    : self
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 1>&1
+    EOI
+    buildfile:11:8: error: stdout merge redirect file descriptor must be 2
+    EOE
+
+    : missed
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 1>&
+    EOI
+    buildfile:11:8: error: missing stdout file descriptor
+    EOE
+  }
+
+  : err
+  {
+    : out
+    :
+    $* <<EOI >>EOO
+    cmd 2>&1
+    EOI
+    cmd 2>&1
+    EOO
+
+    : no-mutual
+    :
+    $* <<EOI >>EOO
+    cmd 1>&2 2>&1 >a
+    EOI
+    cmd >a 2>&1
+    EOO
+
+    : not-descriptor
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 2>&a
+    EOI
+    buildfile:11:8: error: stderr merge redirect file descriptor must be 1
+    EOE
+
+    : self
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 2>&2
+    EOI
+    buildfile:11:8: error: stderr merge redirect file descriptor must be 1
+    EOE
+
+    : missed
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 2>&
+    EOI
+    buildfile:11:8: error: missing stderr file descriptor
+    EOE
+  }
+
+  : mutual
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd 1>&2 2>&1
+  EOI
+  buildfile:11:14: error: stdout and stderr redirected to each other
+  EOE
+}
diff --git a/libbuild2/build/script/parser+regex.test.testscript b/libbuild2/build/script/parser+regex.test.testscript
new file mode 100644
index 0000000..4a47e73
--- /dev/null
+++ b/libbuild2/build/script/parser+regex.test.testscript
@@ -0,0 +1,222 @@
+# file      : libbuild2/build/script/parser+regex.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+: here-string
+:
+{
+  : stdout
+  :
+  {
+    : missed
+    :
+    $* <'cmd >~' 2>>EOE != 0
+    buildfile:11:7: error: missing stdout here-string regex
+    EOE
+
+    : no-introducer
+    :
+    $* <'cmd >~""' 2>>EOE != 0
+    buildfile:11:7: error: no introducer character in stdout regex redirect
+    EOE
+
+    : no-term-introducer
+    :
+    $* <'cmd >~/' 2>>EOE != 0
+    buildfile:11:7: error: no closing introducer character in stdout regex redirect
+    EOE
+
+    : portable-path-introducer
+    :
+    $* <'cmd >/~/foo/' 2>>EOE != 0
+    buildfile:11:8: error: portable path modifier and '/' introducer in stdout regex redirect
+    EOE
+
+    : empty
+    :
+    $* <'cmd >~//' 2>>EOE != 0
+    buildfile:11:7: error: stdout regex redirect is empty
+    EOE
+
+    : no-flags
+    :
+    $* <'cmd >~/fo*/' >'cmd >~/fo*/'
+
+    : idot
+    :
+    $* <'cmd >~/fo*/d' >'cmd >~/fo*/d'
+
+    : icase
+    :
+    $* <'cmd >~/fo*/i' >'cmd >~/fo*/i'
+
+    : invalid-flags1
+    :
+    $* <'cmd >~/foo/z' 2>>EOE != 0
+    buildfile:11:7: error: junk at the end of stdout regex redirect
+    EOE
+
+    : invalid-flags2
+    :
+    $* <'cmd >~/foo/iz' 2>>EOE != 0
+    buildfile:11:7: error: junk at the end of stdout regex redirect
+    EOE
+
+    : no-newline
+    :
+    $* <'cmd >:~/fo*/' >'cmd >:~/fo*/'
+  }
+
+  : stderr
+  :
+  {
+    : missed
+    :
+    $* <'cmd 2>~' 2>>EOE != 0
+    buildfile:11:8: error: missing stderr here-string regex
+    EOE
+
+    : no-introducer
+    :
+    : Note that there is no need to reproduce all the errors as for stdout.
+    : All we need is to make sure that the proper description is passed to
+    : the parse_regex() function.
+    :
+    $* <'cmd 2>~""' 2>>EOE != 0
+    buildfile:11:8: error: no introducer character in stderr regex redirect
+    EOE
+  }
+
+  : modifier-last
+  :
+  $* <'cmd >~/x' 2>>EOE != 0
+  buildfile:11:7: error: no closing introducer character in stdout regex redirect
+  EOE
+}
+
+: here-doc
+:
+{
+  : stdout
+  :
+  {
+    : missed
+    :
+    $* <'cmd >>~' 2>>EOE != 0
+    buildfile:11:8: error: expected here-document regex end marker
+    EOE
+
+    : portable-path-introducer
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd >>/~/EOO/
+    foo
+    EOO
+    EOI
+    buildfile:11:5: error: portable path modifier and '/' introducer in here-document regex end marker
+    EOE
+
+    : unterminated-line-char
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd >>~/EOO/
+    /
+    EOO
+    EOI
+    buildfile:12:1: error: no syntax line characters
+    EOE
+
+    : empty
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd >>:~/EOO/
+    EOO
+    EOI
+    buildfile:12:1: error: empty here-document regex
+    EOE
+
+    : no-flags
+    :
+    $* <<EOI >>EOO
+    cmd 2>>~/EOE/
+    foo
+    /?
+    /foo/
+    /foo/*
+    /foo/i
+    /foo/i*
+
+    //
+    //*
+    EOE
+    EOI
+    cmd 2>>~/EOE/
+    foo
+    /?
+    /foo/
+    /foo/*
+    /foo/i
+    /foo/i*
+
+    //
+    //*
+    EOE
+    EOO
+
+    : no-newline
+    :
+    $* <'cmd >:~/fo*/' >'cmd >:~/fo*/'
+    $* <<EOI >>EOO
+    cmd 2>>:~/EOE/
+    foo
+    EOE
+    EOI
+    cmd 2>>:~/EOE/
+    foo
+    EOE
+    EOO
+
+    : end-marker-restore
+    :
+    {
+      : idot
+      :
+      $* <<EOI >>EOO
+      cmd 2>>~/EOE/d
+      foo
+      EOE
+      EOI
+      cmd 2>>~/EOE/d
+      foo
+      EOE
+      EOO
+
+      : icase
+      :
+      $* <<EOI >>EOO
+      cmd 2>>~/EOE/i
+      foo
+      EOE
+      EOI
+      cmd 2>>~/EOE/i
+      foo
+      EOE
+      EOO
+    }
+  }
+
+  : stderr
+  :
+  {
+    : missed
+    :
+    $* <'cmd 2>>~' 2>>EOE != 0
+    buildfile:11:9: error: expected here-document regex end marker
+    EOE
+  }
+
+  : modifier-last
+  :
+  $* <'cmd >>~:/FOO/' 2>>EOE != 0
+  buildfile:11:5: error: no closing introducer character in here-document regex end marker
+  EOE
+}
diff --git a/libbuild2/build/script/parser+variable.test.testscript b/libbuild2/build/script/parser+variable.test.testscript
new file mode 100644
index 0000000..2d9bb1e
--- /dev/null
+++ b/libbuild2/build/script/parser+variable.test.testscript
@@ -0,0 +1,41 @@
+# file      : libbuild2/build/script/parser+variable.test.testscript
+# license   : MIT; see accompanying LICENSE file
+
+: assignment
+:
+$* <<EOI >>EOO
+a = b
+echo $a
+EOI
+echo b
+EOO
+
+: primary-target
+:
+$* <<EOI >>EOO
+echo $>
+EOI
+echo driver
+EOO
+
+: no-newline
+:
+$* <:'echo a' 2>>EOE != 0
+buildfile:11:7: error: expected newline instead of <end of file>
+EOE
+
+: set-primary-target
+:
+$* <<EOI 2>>EOE != 0
+> = a
+EOI
+buildfile:11:1: error: missing program
+EOE
+
+: empty-name
+:
+$* <<EOI 2>>EOE != 0
+= b
+EOI
+buildfile:11:1: error: missing variable name
+EOE
diff --git a/libbuild2/build/script/parser.cxx b/libbuild2/build/script/parser.cxx
new file mode 100644
index 0000000..4bdf5c7
--- /dev/null
+++ b/libbuild2/build/script/parser.cxx
@@ -0,0 +1,337 @@
+// file      : libbuild2/build/script/parser.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/build/script/parser.hxx>
+
+#include <libbuild2/build/script/lexer.hxx>
+#include <libbuild2/build/script/runner.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      using type = token_type;
+
+      //
+      // Pre-parse.
+      //
+
+      void parser::
+      pre_parse (istream& is, const path_name& pn, uint64_t line, script& s)
+      {
+        path_ = &pn;
+
+        pre_parse_ = true;
+
+        lexer l (is, *path_, line, lexer_mode::command_line);
+        set_lexer (&l);
+
+        script_ = &s;
+        runner_ = nullptr;
+        environment_ = nullptr;
+
+        script_->start_loc = location (*path_, line, 1);
+
+        token t (pre_parse_script ());
+
+        assert (t.type == type::eos);
+
+        script_->end_loc = get_location (t);
+      }
+
+      token parser::
+      pre_parse_script ()
+      {
+        // enter: next token is first token of the script
+        // leave: eos (returned)
+
+        token t;
+        type tt;
+
+        // Parse lines until we see eos.
+        //
+        for (;;)
+        {
+          // Start lexing each line.
+          //
+          tt = peek (lexer_mode::first_token);
+
+          // Determine the line type by peeking at the first token.
+          //
+          switch (tt)
+          {
+          case type::eos:
+            {
+              next (t, tt);
+              return t;
+            }
+          default:
+            {
+              pre_parse_line (t, tt);
+              assert (tt == type::newline);
+              break;
+            }
+          }
+        }
+      }
+
+      void parser::
+      pre_parse_line (token& t, type& tt, bool if_line)
+      {
+        // Determine the line type/start token.
+        //
+        line_type lt (
+          pre_parse_line_start (t, tt, lexer_mode::second_token));
+
+        line ln;
+        switch (lt)
+        {
+        case line_type::var:
+          {
+            // Check if we are trying to modify any of the special variables
+            // ($>).
+            //
+            string& n (t.value);
+
+            if (n == ">")
+              fail (t) << "attempt to set '" << n << "' variable";
+
+            // Pre-enter the variable.
+            //
+            ln.var = &script_->var_pool.insert (move (n));
+
+            next (t, tt); // Assignment kind.
+
+            mode (lexer_mode::variable_line);
+            parse_variable_line (t, tt);
+
+            if (tt != type::newline)
+              fail (t) << "expected newline instead of " << t;
+
+            break;
+          }
+        case line_type::cmd_elif:
+        case line_type::cmd_elifn:
+        case line_type::cmd_else:
+        case line_type::cmd_end:
+          {
+            if (!if_line)
+            {
+              fail (t) << lt << " without preceding 'if'";
+            }
+          }
+          // Fall through.
+        case line_type::cmd_if:
+        case line_type::cmd_ifn:
+          next (t, tt); // Skip to start of command.
+          // Fall through.
+        case line_type::cmd:
+          {
+            pair<command_expr, here_docs> p;
+
+            if (lt != line_type::cmd_else && lt != line_type::cmd_end)
+              p = parse_command_expr (t, tt);
+
+            if (tt != type::newline)
+              fail (t) << "expected newline instead of " << t;
+
+            parse_here_documents (t, tt, p);
+            break;
+          }
+        }
+
+        assert (tt == type::newline);
+
+        ln.type = lt;
+        ln.tokens = replay_data ();
+        script_->lines.push_back (move (ln));
+
+        if (lt == line_type::cmd_if || lt == line_type::cmd_ifn)
+        {
+          tt = peek (lexer_mode::first_token);
+
+          pre_parse_if_else (t, tt);
+        }
+      }
+
+      void parser::
+      pre_parse_if_else (token& t, type& tt)
+      {
+        // enter: peeked first token of next line (type in tt)
+        // leave: newline
+
+        // Parse lines until we see closing 'end'. Nested if-else blocks are
+        // handled recursively.
+        //
+        for (line_type bt (line_type::cmd_if); // Current block.
+             ;
+             tt = peek (lexer_mode::first_token))
+        {
+          const location ll (get_location (peeked ()));
+
+          if (tt == type::eos)
+            fail (ll) << "expected closing 'end'";
+
+          // Parse one line. Note that this one line can still be multiple
+          // lines in case of if-else. In this case we want to view it as
+          // cmd_if, not cmd_end. Thus remember the start position of the
+          // next logical line.
+          //
+          size_t i (script_->lines.size ());
+
+          pre_parse_line (t, tt, true /* if_line */);
+          assert (tt == type::newline);
+
+          line_type lt (script_->lines[i].type);
+
+          // First take care of 'end'.
+          //
+          if (lt == line_type::cmd_end)
+            return;
+
+          // Check if-else block sequencing.
+          //
+          if (bt == line_type::cmd_else)
+          {
+            if (lt == line_type::cmd_else ||
+                lt == line_type::cmd_elif ||
+                lt == line_type::cmd_elifn)
+              fail (ll) << lt << " after " << bt;
+          }
+
+          // Update current if-else block.
+          //
+          switch (lt)
+          {
+          case line_type::cmd_elif:
+          case line_type::cmd_elifn: bt = line_type::cmd_elif; break;
+          case line_type::cmd_else:  bt = line_type::cmd_else; break;
+          default: break;
+          }
+        }
+      }
+
+      command_expr parser::
+      parse_command_line (token& t, type& tt)
+      {
+        // enter: first token of the command line
+        // leave: <newline>
+
+        // Note: this one is only used during execution.
+        //
+        assert (!pre_parse_);
+
+        pair<command_expr, here_docs> p (parse_command_expr (t, tt));
+        assert (tt == type::newline);
+
+        parse_here_documents (t, tt, p);
+        assert (tt == type::newline);
+
+        return move (p.first);
+      }
+
+      //
+      // Execute.
+      //
+
+      void parser::
+      execute (environment& e, runner& r)
+      {
+        path_ = nullptr; // Set by replays.
+
+        pre_parse_ = false;
+
+        set_lexer (nullptr);
+
+        script_ = nullptr;
+        runner_ = &r;
+        environment_ = &e;
+
+        exec_script ();
+      }
+
+      void parser::
+      exec_script ()
+      {
+        const script& s (environment_->script);
+
+        runner_->enter (*environment_, s.start_loc);
+
+        // Note that we rely on "small function object" optimization for the
+        // exec_*() lambdas.
+        //
+        auto exec_set = [this] (const variable& var,
+                                token& t, build2::script::token_type& tt,
+                                const location&)
+        {
+          next (t, tt);
+          type kind (tt); // Assignment kind.
+
+          mode (lexer_mode::variable_line);
+          value rhs (parse_variable_line (t, tt));
+
+          assert (tt == type::newline);
+
+          // Assign.
+          //
+          value& lhs (kind == type::assign
+                      ? environment_->assign (var)
+                      : environment_->append (var));
+
+          apply_value_attributes (&var, lhs, move (rhs), kind);
+        };
+
+        auto exec_cmd = [this] (token& t, build2::script::token_type& tt,
+                                size_t li,
+                                bool single,
+                                const location& ll)
+        {
+          // We use the 0 index to signal that this is the only command.
+          //
+          if (single)
+            li = 0;
+
+          command_expr ce (
+            parse_command_line (t, static_cast<token_type&> (tt)));
+
+          runner_->run (*environment_, ce, li, ll);
+        };
+
+        auto exec_if = [this] (token& t, build2::script::token_type& tt,
+                               size_t li,
+                               const location& ll)
+        {
+          command_expr ce (
+            parse_command_line (t, static_cast<token_type&> (tt)));
+
+          // Assume if-else always involves multiple commands.
+          //
+          return runner_->run_if (*environment_, ce, li, ll);
+        };
+
+        size_t li (1);
+
+        exec_lines (s.lines.begin (), s.lines.end (),
+                    exec_set, exec_cmd, exec_if,
+                    li);
+
+        runner_->leave (*environment_, s.end_loc);
+      }
+
+      lookup parser::
+      lookup_variable (name&& qual, string&& name, const location& loc)
+      {
+        assert (!pre_parse_);
+
+        if (!qual.empty ())
+          fail (loc) << "qualified variable name";
+
+        return environment_->lookup (name);
+      }
+    }
+  }
+}
diff --git a/libbuild2/build/script/parser.hxx b/libbuild2/build/script/parser.hxx
new file mode 100644
index 0000000..a8ffb25
--- /dev/null
+++ b/libbuild2/build/script/parser.hxx
@@ -0,0 +1,92 @@
+// file      : libbuild2/build/script/parser.hxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_BUILD_SCRIPT_PARSER_HXX
+#define LIBBUILD2_BUILD_SCRIPT_PARSER_HXX
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/forward.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/diagnostics.hxx>
+
+#include <libbuild2/script/parser.hxx>
+
+#include <libbuild2/build/script/token.hxx>
+#include <libbuild2/build/script/script.hxx>
+
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      class runner;
+
+      class parser: public build2::script::parser
+      {
+        // Pre-parse. Issue diagnostics and throw failed in case of an error.
+        //
+      public:
+        parser (context& c): build2::script::parser (c) {}
+
+        void
+        pre_parse (istream&, const path_name&, uint64_t line, script&);
+
+        // Recursive descent parser.
+        //
+        // Usually (but not always) parse functions receive the token/type
+        // from which it should start consuming and in return the token/type
+        // should contain the first token that has not been consumed.
+        //
+        // Functions that are called parse_*() rather than pre_parse_*() are
+        // used for both stages.
+        //
+      protected:
+        token
+        pre_parse_script ();
+
+        void
+        pre_parse_line (token&, token_type&, bool if_line = false);
+
+        void
+        pre_parse_if_else (token&, token_type&);
+
+        command_expr
+        parse_command_line (token&, token_type&);
+
+        // Workaround for GCC 4.9 that fails to compile the base class
+        // protected member function call from a lambda defined in the derived
+        // class.
+        //
+        using build2::parser::apply_value_attributes;
+
+        // Execute. Issue diagnostics and throw failed in case of an error.
+        //
+      public:
+        void
+        execute (environment&, runner&);
+
+      protected:
+        void
+        exec_script ();
+
+        // Customization hooks.
+        //
+      protected:
+        virtual lookup
+        lookup_variable (name&&, string&&, const location&) override;
+
+      protected:
+        script* script_;
+
+        // Execute state.
+        //
+        runner* runner_;
+        environment* environment_;
+      };
+    }
+  }
+}
+
+#endif // LIBBUILD2_BUILD_SCRIPT_PARSER_HXX
diff --git a/libbuild2/build/script/parser.test.cxx b/libbuild2/build/script/parser.test.cxx
new file mode 100644
index 0000000..2763464
--- /dev/null
+++ b/libbuild2/build/script/parser.test.cxx
@@ -0,0 +1,145 @@
+// file      : libbuild2/build/script/parser.test.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#include <cassert>
+#include <iostream>
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/target.hxx>
+#include <libbuild2/context.hxx>
+#include <libbuild2/scheduler.hxx>
+
+#include <libbuild2/build/script/parser.hxx>
+#include <libbuild2/build/script/runner.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      class print_runner: public runner
+      {
+      public:
+        print_runner (bool line): line_ (line) {}
+
+        virtual void
+        enter (environment&, const location&) override {}
+
+        virtual void
+        run (environment&,
+             const command_expr& e,
+             size_t i,
+             const location&) override
+        {
+          cout << e;
+
+          if (line_)
+            cout << " # " << i;
+
+          cout << endl;
+        }
+
+        virtual bool
+        run_if (environment&,
+                const command_expr& e,
+                size_t i,
+                const location&) override
+        {
+          cout << "? " << e;
+
+          if (line_)
+            cout << " # " << i;
+
+          cout << endl;
+
+          return e.back ().pipe.back ().program.string () == "true";
+        }
+
+        virtual void
+        leave (environment&, const location&) override {}
+
+      private:
+        bool line_;
+      };
+
+      // Usage: argv[0] [-l]
+      //
+      int
+      main (int argc, char* argv[])
+      {
+        tracer trace ("main");
+
+        // Fake build system driver, default verbosity.
+        //
+        init_diag (1);
+        init (nullptr, argv[0]);
+
+        // Serial execution.
+        //
+        scheduler sched (1);
+        global_mutexes mutexes (1);
+        context ctx (sched, mutexes);
+
+        bool line (false);
+
+        for (int i (1); i != argc; ++i)
+        {
+          string a (argv[i]);
+
+          if (a == "-l")
+            line = true;
+          else
+            assert (false);
+        }
+
+        try
+        {
+          cin.exceptions (istream::failbit | istream::badbit);
+
+          // Enter mock target. Use fixed name and path so that we can use
+          // them in expected results. Strictly speaking target path should
+          // be absolute. However, the buildscript implementation doesn't
+          // really care.
+          //
+          file& tt (
+            ctx.targets.insert<file> (work,
+                                      dir_path (),
+                                      "driver",
+                                      string (),
+                                      trace));
+
+          tt.path (path ("driver"));
+
+          // Parse and run.
+          //
+          path_name nm ("buildfile");
+
+          script s;
+          parser p (ctx);
+          p.pre_parse (cin, nm, 11 /* line */, s);
+
+          environment e (s, tt);
+          print_runner r (line);
+          p.execute (e, r);
+        }
+        catch (const failed&)
+        {
+          return 1;
+        }
+
+        return 0;
+      }
+    }
+  }
+}
+
+int
+main (int argc, char* argv[])
+{
+  return build2::build::script::main (argc, argv);
+}
diff --git a/libbuild2/build/script/runner.cxx b/libbuild2/build/script/runner.cxx
new file mode 100644
index 0000000..f52d1c0
--- /dev/null
+++ b/libbuild2/build/script/runner.cxx
@@ -0,0 +1,50 @@
+// file      : libbuild2/build/script/runner.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/build/script/runner.hxx>
+
+#include <libbuild2/script/run.hxx>
+
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      void default_runner::
+      enter (environment&, const location&)
+      {
+        // Noop.
+      }
+
+      void default_runner::
+      leave (environment& env, const location& ll)
+      {
+        clean (env, ll);
+      }
+
+      void default_runner::
+      run (environment& env,
+           const command_expr& expr,
+           size_t li,
+           const location& ll)
+      {
+        if (verb >= 3)
+          text << ":  " << expr;
+
+        build2::script::run (env, expr, li, ll);
+      }
+
+      bool default_runner::
+      run_if (environment& env,
+              const command_expr& expr,
+              size_t li, const location& ll)
+      {
+        if (verb >= 3)
+          text << ": ?" << expr;
+
+        return build2::script::run_if (env, expr, li, ll);
+      }
+    }
+  }
+}
diff --git a/libbuild2/build/script/runner.hxx b/libbuild2/build/script/runner.hxx
new file mode 100644
index 0000000..db211df
--- /dev/null
+++ b/libbuild2/build/script/runner.hxx
@@ -0,0 +1,78 @@
+// file      : libbuild2/build/script/runner.hxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_BUILD_SCRIPT_RUNNER_HXX
+#define LIBBUILD2_BUILD_SCRIPT_RUNNER_HXX
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/build/script/script.hxx>
+
+namespace build2
+{
+  namespace build
+  {
+    struct common;
+
+    namespace script
+    {
+      class runner
+      {
+      public:
+        // Location is the script start location (for diagnostics, etc).
+        //
+        virtual void
+        enter (environment&, const location&) = 0;
+
+        // Index is the 1-base index of this command line in the command list.
+        // If it is 0 then it means there is only one command. This
+        // information can be used, for example, to derive file names.
+        //
+        // Location is the start position of this command line in the script.
+        // It can be used in diagnostics.
+        //
+        virtual void
+        run (environment&,
+             const command_expr&,
+             size_t index,
+             const location&) = 0;
+
+        virtual bool
+        run_if (environment&,
+                const command_expr&,
+                size_t,
+                const location&) = 0;
+
+        // Location is the script end location (for diagnostics, etc).
+        //
+        virtual void
+        leave (environment&, const location&) = 0;
+      };
+
+      class default_runner: public runner
+      {
+      public:
+        virtual void
+        enter (environment&, const location&) override;
+
+        virtual void
+        run (environment&,
+             const command_expr&,
+             size_t,
+             const location&) override;
+
+        virtual bool
+        run_if (environment&,
+                const command_expr&,
+                size_t,
+                const location&) override;
+
+        virtual void
+        leave (environment&, const location&) override;
+      };
+    }
+  }
+}
+
+#endif // LIBBUILD2_BUILD_SCRIPT_RUNNER_HXX
diff --git a/libbuild2/build/script/script.cxx b/libbuild2/build/script/script.cxx
new file mode 100644
index 0000000..26fe006
--- /dev/null
+++ b/libbuild2/build/script/script.cxx
@@ -0,0 +1,156 @@
+// file      : libbuild2/build/script/script.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/build/script/script.hxx>
+
+#include <libbuild2/target.hxx>
+
+#include <libbuild2/script/parser.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      // script
+      //
+      script::
+      script ()
+          : primary_target_var (var_pool.insert<path> (">"))
+      {
+      }
+
+      // environment
+      //
+      static const string wd_name ("current directory");
+
+      environment::
+      environment (const build::script::script& s, const target& pt)
+          : build2::script::environment (
+              pt.ctx,
+              cast<target_triplet> (pt.ctx.global_scope["build.host"]),
+              work,
+              wd_name),
+            script (s),
+            vars (context, false /* global */),
+            primary_target (pt)
+      {
+        // Set the $> variable.
+        //
+        {
+          value& v (assign (s.primary_target_var));
+
+          if (auto* t = pt.is_a<path_target> ())
+            v = t->path ();
+          else
+            fail << "target " << pt << " is not path-based";
+        }
+      }
+
+      void environment::
+      set_variable (string&& nm, names&& val, const string& attrs)
+      {
+        // Set the variable value and attributes. Note that we need to aquire
+        // unique lock before potentially changing the script's variable
+        // pool. The obtained variable reference can safelly be used with no
+        // locking as the variable pool is an associative container
+        // (underneath) and we are only adding new variables into it.
+        //
+        ulock ul (script.var_pool_mutex);
+
+        const variable& var (
+          const_cast<build::script::script&> (script).var_pool.
+          insert (move (nm)));
+
+        ul.unlock ();
+
+        value& lhs (assign (var));
+
+        // If there are no attributes specified then the variable assignment
+        // is straightforward. Otherwise we will use the build2 parser helper
+        // function.
+        //
+        if (attrs.empty ())
+          lhs.assign (move (val), &var);
+        else
+        {
+          build2::script::parser p (context);
+          p.apply_value_attributes (&var,
+                                    lhs,
+                                    value (move (val)),
+                                    attrs,
+                                    token_type::assign,
+                                    path_name ("<attributes>"));
+        }
+      }
+
+      lookup environment::
+      lookup (const variable& var) const
+      {
+        auto p (vars.lookup (var));
+        if (p.first != nullptr)
+          return lookup_type (*p.first, p.second, vars);
+
+        return lookup_in_buildfile (var.name);
+      }
+
+      lookup environment::
+      lookup (const string& name) const
+      {
+        // Every variable that is ever set in a script has been pre-entered
+        // during pre-parse or introduced with the set builtin during
+        // execution. Which means that if one is not found in the script pool
+        // then it can only possibly be set in the buildfile.
+        //
+        // Note that we need to acquire the variable pool lock. The pool can
+        // be changed from multiple threads by the set builtin. The obtained
+        // variable pointer can safelly be used with no locking as the
+        // variable pool is an associative container (underneath) and we are
+        // only adding new variables into it.
+        //
+        const variable* pvar (nullptr);
+
+        slock sl (script.var_pool_mutex);
+        pvar = script.var_pool.find (name);
+        sl.unlock ();
+
+        return pvar != nullptr ? lookup (*pvar) : lookup_in_buildfile (name);
+      }
+
+      lookup environment::
+      lookup_in_buildfile (const string& n) const
+      {
+        // Switch to the corresponding buildfile variable. Note that we don't
+        // want to insert a new variable into the pool (we might be running
+        // in parallel). Plus, if there is no such variable, then we cannot
+        // possibly find any value.
+        //
+        const variable* pvar (context.var_pool.find (n));
+
+        if (pvar == nullptr)
+          return lookup_type ();
+
+        return primary_target[*pvar];
+      }
+
+      value& environment::
+      append (const variable& var)
+      {
+        auto l (lookup (var));
+
+        if (l.defined () && l.belongs (*this)) // Existing var.
+          return vars.modify (l);
+
+        value& r (assign (var)); // NULL.
+
+        if (l.defined ())
+          r = *l; // Copy value (and type) from the outer scope.
+
+        return r;
+      }
+    }
+  }
+}
diff --git a/libbuild2/build/script/script.hxx b/libbuild2/build/script/script.hxx
new file mode 100644
index 0000000..18ed4c4
--- /dev/null
+++ b/libbuild2/build/script/script.hxx
@@ -0,0 +1,111 @@
+// file      : libbuild2/build/script/script.hxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_BUILD_SCRIPT_SCRIPT_HXX
+#define LIBBUILD2_BUILD_SCRIPT_SCRIPT_HXX
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/forward.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/variable.hxx>
+
+#include <libbuild2/script/script.hxx>
+
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      using build2::script::line;
+      using build2::script::line_type;
+      using build2::script::command_expr;
+
+      // Once parsed, the script can be executed in multiple threads with the
+      // state (variable values, etc) maintained by the environment object.
+      //
+      class script
+      {
+      public:
+        build2::script::lines lines;
+
+        variable_pool var_pool;
+        mutable shared_mutex var_pool_mutex;
+
+        const variable& primary_target_var; // $>
+
+        location start_loc;
+        location end_loc;
+
+        script ();
+
+        script (script&&) = delete;
+        script (const script&) = delete;
+        script& operator= (script&&) = delete;
+        script& operator= (const script&) = delete;
+      };
+
+      class environment: public build2::script::environment
+      {
+      public:
+        environment (const script&, const target& primary_target);
+
+        environment (environment&&) = delete;
+        environment (const environment&) = delete;
+        environment& operator= (environment&&) = delete;
+        environment& operator= (const environment&) = delete;
+
+      public:
+        const build::script::script& script;
+
+        // Note that if we pass the variable name as a string, then it will
+        // be looked up in the wrong pool.
+        //
+        variable_map vars;
+
+        const target& primary_target;
+
+        virtual void
+        set_variable (string&& name, names&&, const string& attrs) override;
+
+        // Variables.
+        //
+      public:
+        // Lookup the variable starting from this environment, then the
+        // primary target, and then outer buildfile scopes.
+        //
+        using lookup_type = build2::lookup;
+
+        lookup_type
+        lookup (const variable&) const;
+
+        lookup_type
+        lookup (const string&) const;
+
+        // As above but only look for buildfile variables.
+        //
+        lookup_type
+        lookup_in_buildfile (const string&) const;
+
+        // Return a value suitable for assignment. If the variable does not
+        // exist in this environment's map, then a new one with the NULL value
+        // is added and returned. Otherwise the existing value is returned.
+        //
+        value&
+        assign (const variable& var) {return vars.assign (var);}
+
+        // Return a value suitable for append/prepend. If the variable does
+        // not exist in this environment's map, then outer scopes are searched
+        // for the same variable. If found then a new variable with the found
+        // value is added to the environment and returned. Otherwise this
+        // function proceeds as assign() above.
+        //
+        value&
+        append (const variable&);
+      };
+    }
+  }
+}
+
+#endif // LIBBUILD2_BUILD_SCRIPT_SCRIPT_HXX
diff --git a/libbuild2/build/script/token.cxx b/libbuild2/build/script/token.cxx
new file mode 100644
index 0000000..289dfd2
--- /dev/null
+++ b/libbuild2/build/script/token.cxx
@@ -0,0 +1,23 @@
+// file      : libbuild2/build/script/token.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/build/script/token.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      void
+      token_printer (ostream& os, const token& t, bool d)
+      {
+        // No build script-specific tokens so far.
+        //
+        build2::script::token_printer (os, t, d);
+      }
+    }
+  }
+}
diff --git a/libbuild2/build/script/token.hxx b/libbuild2/build/script/token.hxx
new file mode 100644
index 0000000..4cd90d7
--- /dev/null
+++ b/libbuild2/build/script/token.hxx
@@ -0,0 +1,36 @@
+// file      : libbuild2/build/script/token.hxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_BUILD_SCRIPT_TOKEN_HXX
+#define LIBBUILD2_BUILD_SCRIPT_TOKEN_HXX
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/script/token.hxx>
+
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      struct token_type: build2::script::token_type
+      {
+        using base_type = build2::script::token_type;
+
+        // No build script-specific tokens so far.
+        //
+
+        token_type () = default;
+        token_type (value_type v): base_type (v) {}
+        token_type (build2::token_type v): base_type (v) {}
+      };
+
+      void
+      token_printer (ostream&, const token&, bool);
+    }
+  }
+}
+
+#endif // LIBBUILD2_BUILD_SCRIPT_TOKEN_HXX