Implement "see through" installation semantics for utility libraries

3 files changed, 39 insertions, 14 deletions

diff --git a/build2/install/init.cxx b/build2/install/init.cxx
index 6a5114d..1d51be2 100644
--- a/build2/install/init.cxx
+++ b/build2/install/init.cxx
@@ -124,9 +124,6 @@ namespace build2
         var_pool.rw (r).insert<bool> (string ("install.") + n + ".subdirs");
     }
 
-    static const alias_rule alias_;
-    static const file_rule file_;
-
     void
     boot (scope& r, const location&, unique_ptr<module_base>&)
     {
@@ -200,11 +197,16 @@ namespace build2
 
       // Register our alias and file rules.
       //
-      bs.rules.insert<alias> (perform_install_id,   "install.alias", alias_);
-      bs.rules.insert<alias> (perform_uninstall_id, "uninstall.alias", alias_);
+      {
+        const auto& ar (alias_rule::instance);
+        const auto& fr (file_rule::instance);
 
-      bs.rules.insert<file> (perform_install_id,   "install.file", file_);
-      bs.rules.insert<file> (perform_uninstall_id, "uinstall.file", file_);
+        bs.rules.insert<alias> (perform_install_id,   "install.alias", ar);
+        bs.rules.insert<alias> (perform_uninstall_id, "uninstall.alias", ar);
+
+        bs.rules.insert<file> (perform_install_id,   "install.file", fr);
+        bs.rules.insert<file> (perform_uninstall_id, "uinstall.file", fr);
+      }
 
       // Configuration.
       //
diff --git a/build2/install/rule.cxx b/build2/install/rule.cxx
index 8611247..f2fc233 100644
--- a/build2/install/rule.cxx
+++ b/build2/install/rule.cxx
@@ -38,20 +38,32 @@ namespace build2
 
     // alias_rule
     //
+    const alias_rule alias_rule::instance;
+
     match_result alias_rule::
     match (action, target&, const string&) const
     {
       return true;
     }
 
+    const target* alias_rule::
+    filter (action, const target& t, prerequisite_member p) const
+    {
+      return &p.search (t);
+    }
+
     recipe alias_rule::
     apply (action a, target& t) const
     {
       tracer trace ("install::alias_rule::apply");
 
-      for (const prerequisite& p: group_prerequisites (t))
+      for (prerequisite_member p: group_prerequisite_members (a, t))
       {
-        const target& pt (search (t, p));
+        // Let a customized rule have its say.
+        //
+        const target* pt (filter (a, t, p));
+        if (pt == nullptr)
+          continue;
 
         // Check if this prerequisite is explicitly "not installable",
         // that is, there is the 'install' variable and its value is
@@ -65,16 +77,15 @@ namespace build2
         //
         // Note: not the same as lookup() above.
         //
-        auto l (pt["install"]);
-
+        auto l ((*pt)["install"]);
         if (l && cast<path> (l).string () == "false")
         {
-          l5 ([&]{trace << "ignoring " << pt;});
+          l5 ([&]{trace << "ignoring " << *pt;});
           continue;
         }
 
-        build2::match (a, pt);
-        t.prerequisite_targets.push_back (&pt);
+        build2::match (a, *pt);
+        t.prerequisite_targets.push_back (pt);
       }
 
       return default_recipe;
@@ -82,6 +93,8 @@ namespace build2
 
     // file_rule
     //
+    const file_rule file_rule::instance;
+
     struct match_data
     {
       bool install;
diff --git a/build2/install/rule.hxx b/build2/install/rule.hxx
index 76259c9..ad0d8ec 100644
--- a/build2/install/rule.hxx
+++ b/build2/install/rule.hxx
@@ -19,6 +19,8 @@ namespace build2
     class alias_rule: public rule
     {
     public:
+      static const alias_rule instance;
+
       alias_rule () {}
 
       virtual match_result
@@ -26,6 +28,12 @@ namespace build2
 
       virtual recipe
       apply (action, target&) const override;
+
+      // Return NULL if this prerequisite should be ignored and pointer to its
+      // target otherwise. The default implementation accepts all prerequsites.
+      //
+      virtual const target*
+      filter (action, const target&, prerequisite_member) const;
     };
 
     struct install_dir;
@@ -33,6 +41,8 @@ namespace build2
     class file_rule: public rule
     {
     public:
+      static const file_rule instance;
+
       file_rule () {}
 
       virtual match_result