Implement auto-import of development build2 build

10 files changed, 96 insertions, 11 deletions

diff --git a/build2/b.cxx b/build2/b.cxx
index 49a4d34..27a9cd0 100644
--- a/build2/b.cxx
+++ b/build2/b.cxx
@@ -609,6 +609,7 @@ main (int argc, char* argv[])
       trace << "work: " << work;
       trace << "home: " << home;
       trace << "path: " << (p ? *p : "<NULL>");
+      trace << "type: " << (build_installed ? "installed" : "development");
       trace << "jobs: " << jobs;
     }
 
diff --git a/build2/cc/link-rule.cxx b/build2/cc/link-rule.cxx
index fa6d5e4..ce5fce9 100644
--- a/build2/cc/link-rule.cxx
+++ b/build2/cc/link-rule.cxx
@@ -1821,7 +1821,10 @@ namespace build2
           if (lookup l = p.prerequisite.vars[var_fi])
           {
             if (cast<bool> (l) != for_install)
+            {
+              l5 ([&]{trace << "excluding " << *pt << " due to for_install";});
               pt = nullptr;
+            }
           }
         }
       }
diff --git a/libbuild2/buildfile b/libbuild2/buildfile
index 7d91e08..deda991 100644
--- a/libbuild2/buildfile
+++ b/libbuild2/buildfile
@@ -9,8 +9,14 @@
 
 import int_libs = libbutl%lib{butl}
 
-lib{build2}: libul{build2}: {hxx ixx txx cxx}{* -config -version -*.test...} \
-                            {hxx}{config version}
+lib{build2}: libul{build2}:                                            \
+  {hxx ixx txx cxx}{* -utility-installed -config -version -*.test...} \
+  {hxx}{config version}
+
+# Note that this won't work on libul{} since it's never installed.
+#
+lib{build2}: cxx{utility-installed}: for_install = true
+liba{build2}: bin.whole = true # See utility-installed.cxx.
 
 # These are "core modules" that come bundled with libbuild2 (see also unit
 # tests loop below). Note that the build system core can still function
@@ -66,9 +72,15 @@ for t:         cxx{ *.test...} \
 obja{*}: cxx.poptions += -DLIBBUILD2_STATIC_BUILD
 objs{*}: cxx.poptions += -DLIBBUILD2_SHARED_BUILD
 
-# Pass our compiler target to be used as libbuild2 host.
+# Pass our compiler target to be used as build2 host and our out_root to
+# be used as the build system import path.
 #
-obj{context}:  cxx.poptions += -DBUILD2_HOST_TRIPLET=\"$cxx.target\"
+obj{context}:
+{
+  cxx.poptions += "-DBUILD2_HOST_TRIPLET=\"$cxx.target\""
+  cxx.poptions += "-DBUILD2_IMPORT_PATH=\"$out_root\""
+}
+
 obja{context}: cxx.poptions += -DLIBBUILD2_STATIC_BUILD
 objs{context}: cxx.poptions += -DLIBBUILD2_SHARED_BUILD
 
diff --git a/libbuild2/context.cxx b/libbuild2/context.cxx
index e35f308..a715c59 100644
--- a/libbuild2/context.cxx
+++ b/libbuild2/context.cxx
@@ -124,6 +124,16 @@ namespace build2
                     path (argv0.recall_string ()),
                     path (argv0.effect));
 
+    // Build system import path for modules. We only set it for the
+    // development build.
+    //
+    var_import_build2 = &vp.insert<abs_dir_path> ("import.build2");
+
+#ifndef BUILD2_BOOTSTRAP
+    if (!build_installed)
+      gs.assign (var_import_build2) = abs_dir_path (BUILD2_IMPORT_PATH);
+#endif
+
     // Build system verbosity level.
     //
     gs.assign<uint64_t> ("build.verbosity") = verb;
diff --git a/libbuild2/context.hxx b/libbuild2/context.hxx
index 338b8a1..57ae65d 100644
--- a/libbuild2/context.hxx
+++ b/libbuild2/context.hxx
@@ -315,8 +315,9 @@ namespace build2
     //
     const variable* var_project_summary;
 
-    // import.target
+    // import.*
     //
+    const variable* var_import_build2;
     const variable* var_import_target;
 
     // [string] target visibility
diff --git a/libbuild2/file.cxx b/libbuild2/file.cxx
index 1c6bb1d..f0215df 100644
--- a/libbuild2/file.cxx
+++ b/libbuild2/file.cxx
@@ -1296,6 +1296,13 @@ namespace build2
     {
       string n ("config.import." + proj.variable ());
 
+      auto skip = [&target, &proj, &trace] ()
+      {
+        target.proj = move (proj);
+        l5 ([&]{trace << "skipping " << target;});
+        return make_pair (move (target), dir_path ());
+      };
+
       // config.import.<proj>
       //
       {
@@ -1318,11 +1325,7 @@ namespace build2
           // to use system-installed).
           //
           if (out_root.empty ())
-          {
-            target.proj = move (proj);
-            l5 ([&]{trace << "skipping " << target;});
-            return make_pair (move (target), dir_path ());
-          }
+            return skip ();
 
           break;
         }
@@ -1383,6 +1386,26 @@ namespace build2
         }
       }
 
+      // import.build2
+      //
+      if (proj == "build2")
+      {
+        // Note that this variable can be set to NULL to disable relying on
+        // the built-in path. We use this in our tests to make sure we are
+        // importing and testing the build system being built and not the one
+        // doing the building.
+        //
+        if (auto l = iroot[ctx.var_import_build2])
+        {
+          out_root = cast<dir_path> (l);
+
+          if (out_root.empty ())
+            return skip ();
+
+          break;
+        }
+      }
+
       // Otherwise search subprojects, starting with our root and then trying
       // outer roots for as long as we are inside an amalgamation.
       //
diff --git a/libbuild2/utility-installed.cxx b/libbuild2/utility-installed.cxx
new file mode 100644
index 0000000..8fcb271
--- /dev/null
+++ b/libbuild2/utility-installed.cxx
@@ -0,0 +1,24 @@
+// file      : libbuild2/utility-installed.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+// Bootstrap build is never condidered installed.
+//
+#ifndef BUILD2_BOOTSTRAP
+
+#include <libbuild2/utility.hxx>
+
+namespace build2
+{
+  struct build_installed_init
+  {
+    build_installed_init ()
+    {
+      build_installed = true;
+    }
+  };
+
+  static build_installed_init init_;
+}
+
+#endif
diff --git a/libbuild2/utility.cxx b/libbuild2/utility.cxx
index ba50c5a..4f6874e 100644
--- a/libbuild2/utility.cxx
+++ b/libbuild2/utility.cxx
@@ -81,6 +81,8 @@ namespace build2
     : (to_string (build_version.major ()) + '.' +
        to_string (build_version.minor ())));
 
+  bool build_installed;
+
   optional<bool> mtime_check_option;
 
   optional<path> config_sub;
diff --git a/libbuild2/utility.hxx b/libbuild2/utility.hxx
index a6a7ac3..d9c530b 100644
--- a/libbuild2/utility.hxx
+++ b/libbuild2/utility.hxx
@@ -142,6 +142,12 @@ namespace build2
   LIBBUILD2_SYMEXPORT extern const standard_version build_version;
   LIBBUILD2_SYMEXPORT extern const string build_version_interface;
 
+  // Whether running installed build.
+  //
+  // Note: only available after static initialization.
+  //
+  LIBBUILD2_SYMEXPORT extern bool build_installed;
+
   // --[no-]mtime-check
   //
   LIBBUILD2_SYMEXPORT extern optional<bool> mtime_check_option;
diff --git a/tests/build/root.build b/tests/build/root.build
index 5398bf8..43d3607 100644
--- a/tests/build/root.build
+++ b/tests/build/root.build
@@ -16,8 +16,11 @@ if ($cxx.class == 'msvc')
 }
 
 # Setup the build system driver that we are testing (which may not be the same
-# as our $build.path).
+# as our $build.path). We also need to disable importation using the built-in
+# path.
 #
+import.build2 = [null]
+
 import b = build2%exe{b}
 testscript{*}: test = $b