Add $is_a(<name>, <target-type>), $filter[_out](<names>, <target-types>) functions

$is_a() returns true if the <name>'s target type is-a <target-type>. Note
that this is a dynamic type check that takes into account target type
inheritance.

$filter[_out]() return names with target types which are-a (filter) or
not are-a (filter_out) one of <target-types>.

In particular, these functions are useful for filtering prerequisite
targets ($<) in ad hoc recipes and rules.

2 files changed, 154 insertions, 12 deletions

diff --git a/libbuild2/functions-name.cxx b/libbuild2/functions-name.cxx
index e5bb366..43de039 100644
--- a/libbuild2/functions-name.cxx
+++ b/libbuild2/functions-name.cxx
@@ -20,25 +20,26 @@ namespace build2
   // out of scope). See scope::find_target_type() for details. Allow out-
   // qualified names (out is discarded).
   //
-  static pair<name, optional<string>>
-  to_target_name (const scope* s, name&& n, const name& o = name ())
+  static pair<const target_type*, optional<string>>
+  to_target_type (const scope* s, name& n, const name& o = name ())
   {
     if (n.pair && !o.directory ())
       fail << "name pair in names";
 
-    optional<string> e;
-
-    if (s != nullptr)
-    {
-      auto rp (s->find_target_type (n, location ()));
+    return s != nullptr
+      ? s->find_target_type (n, location ())
+      : pair<const target_type*, optional<string>> {nullptr, nullopt};
+  }
 
-      if (rp.first != nullptr)
-        n.type = rp.first->name;
+  static pair<name, optional<string>>
+  to_target_name (const scope* s, name&& n, const name& o = name ())
+  {
+    auto rp (to_target_type (s, n, o));
 
-      e = move (rp.second);
-    }
+    if (rp.first != nullptr)
+      n.type = rp.first->name;
 
-    return make_pair (move (n), move (e));
+    return make_pair (move (n), move (rp.second));
   }
 
   const target&
@@ -61,6 +62,72 @@ namespace build2
     return to_target (s, move (ns[0]), move (ns[0].pair ? ns[1] : o));
   }
 
+  static bool
+  is_a (const scope* s, name&& n, const name& o, names&& t)
+  {
+    if (s == nullptr)
+      fail << "name.is_a() called out of scope";
+
+    string tts (convert<string> (move (t)));
+    const target_type* tt (s->find_target_type (tts));
+    if (tt == nullptr)
+      fail << "unknown target type " << tts;
+
+    const target_type* ntt (to_target_type (s, n, o).first);
+    if (ntt == nullptr)
+      fail << "unknown target type " << n.type << " in " << n;
+
+    return ntt->is_a (*tt);
+  }
+
+  static names
+  filter (const scope* s, names ns, names ts, bool out)
+  {
+    if (s == nullptr)
+      fail << "name." << (out ? "filter_out" : "filter")
+           << "() called out of scope";
+
+    small_vector<const target_type*, 1> tts;
+    for (const name& n: ts)
+    {
+      if (!n.simple ())
+        fail << "invalid target type name " << n;
+
+      if (n.pair)
+        fail << "pair in target type name " << n;
+
+      const target_type* tt (s->find_target_type (n.value));
+      if (tt == nullptr)
+        fail << "unknown target type " << n.value;
+
+      tts.push_back (tt);
+    }
+
+    names r;
+    for (auto i (ns.begin ()); i != ns.end (); ++i)
+    {
+      name& n (*i);
+      bool p (n.pair);
+
+      const target_type* ntt (to_target_type (s, n, p ? *++i : name ()).first);
+      if (ntt == nullptr)
+        fail << "unknown target type " << n.type << " in " << n;
+
+      if ((find_if (tts.begin (), tts.end (),
+                    [ntt] (const target_type* tt)
+                    {
+                      return ntt->is_a (*tt);
+                    }) != tts.end ()) != out)
+      {
+        r.push_back (move (n));
+        if (p)
+          r.push_back (move (*i));
+      }
+    }
+
+    return r;
+  }
+
   void
   name_functions (function_map& m)
   {
@@ -186,6 +253,45 @@ namespace build2
       return to_target_name (s, move (n), o).first.proj;
     };
 
+    // $is_a(<name>, <target-type>)
+    //
+    // Return true if the <name>'s target type is-a <target-type>. Note that
+    // this is a dynamic type check that takes into account target type
+    // inheritance.
+    //
+    fn["is_a"] += [](const scope* s, name n, names t)
+    {
+      return is_a (s, move (n), name (), move (t));
+    };
+    fn["is_a"] += [](const scope* s, names ns, names t)
+    {
+      auto i (ns.begin ());
+
+      name& n (*i);
+      const name& o (n.pair ? *++i : name ());
+
+      if (++i != ns.end ())
+        fail << "invalid name value: multiple names"; // Like in convert().
+
+      return is_a (s, move (n), o, move (t));
+    };
+
+    // $filter(<names>, <target-types>)
+    // $filter_out(<names>, <target-types>)
+    //
+    // Return names with target types which are-a (filter) or not are-a
+    // (filter_out) one of <target-types>. See $is_a() for background.
+    //
+    fn["filter"] += [](const scope* s, names ns, names ts)
+    {
+      return filter (s, move (ns), move (ts), false /* out */);
+    };
+
+    fn["filter_out"] += [](const scope* s, names ns, names ts)
+    {
+      return filter (s, move (ns), move (ts), true /* out */);
+    };
+
     // $size(<names>)
     //
     // Return the number of elements in the sequence.
diff --git a/tests/function/name/testscript b/tests/function/name/testscript
index 2fe8e24..6222167 100644
--- a/tests/function/name/testscript
+++ b/tests/function/name/testscript
@@ -3,6 +3,42 @@
 
 .include ../../common.testscript
 
+: is_a
+:
+{
+  $* <'print $is_a(file{foo},    path_target)' >'true'  : basics-true
+  $* <'print $is_a(alias{foo},   path_target)' >'false' : basics-false
+  $* <'print $is_a(file{foo}@./, path_target)' >'true'  : out
+  $* <<EOI                                     >'true'  : derived
+  define txt: file
+  print $is_a(txt{foo}, path_target)
+  EOI
+}
+
+: filter
+:
+{
+  $* <<EOI >'file{foo}@./ txt{baz}' : basics
+  define txt: file
+  print $filter(file{foo}@./ alias{bar} dir{./} txt{baz}, file)
+  EOI
+
+  $* <<EOI >'file{foo}@./ txt{baz}' : basics-out
+  define txt: file
+  print $filter_out(file{foo}@./ alias{bar} dir{./} txt{baz}, alias)
+  EOI
+
+  $* <<EOI >'file{foo}@./ dir{./} txt{baz}' : multiple
+  define txt: file
+  print $filter(file{foo}@./ alias{bar} dir{./} txt{baz}, file dir)
+  EOI
+
+  $* <<EOI >'file{foo}@./ alias{bar}' : multiple-out
+  define txt: file
+  print $filter_out(file{foo}@./ alias{bar} dir{./} txt{baz}, txt dir)
+  EOI
+}
+
 : size
 :
 {