Add support for rule hints

A rule hint is a target attribute, for example:

[rule_hint=cxx] exe{hello}: c{hello}

Rule hints can be used to resolve ambiguity when multiple rules match the same
target as well as to override an unambiguous match.

3 files changed, 18 insertions, 19 deletions

diff --git a/libbuild2/install/init.cxx b/libbuild2/install/init.cxx
index 1bf1623..ef9de05 100644
--- a/libbuild2/install/init.cxx
+++ b/libbuild2/install/init.cxx
@@ -372,19 +372,19 @@ namespace build2
         const auto& gr (group_rule_);
 
         bs.insert_rule<alias> (perform_install_id,   "install.alias", ar);
-        bs.insert_rule<alias> (perform_uninstall_id, "uninstall.alias", ar);
+        bs.insert_rule<alias> (perform_uninstall_id, "install.alias", ar);
 
         bs.insert_rule<fsdir> (perform_install_id,   "install.fsdir", dr);
         bs.insert_rule<fsdir> (perform_uninstall_id, "install.fsdir", dr);
 
         bs.insert_rule<file> (perform_install_id,   "install.file", fr);
-        bs.insert_rule<file> (perform_uninstall_id, "uninstall.file", fr);
+        bs.insert_rule<file> (perform_uninstall_id, "install.file", fr);
 
         // Note: use mtime_target (instead of target) to take precedence over
         // the fallback file rules below.
         //
         bs.insert_rule<mtime_target> (perform_install_id,   "install.group", gr);
-        bs.insert_rule<mtime_target> (perform_uninstall_id, "uninstall.group", gr);
+        bs.insert_rule<mtime_target> (perform_uninstall_id, "install.group", gr);
 
         // Register the fallback file rule for the update-for-[un]install
         // operation, similar to update.
@@ -392,11 +392,10 @@ namespace build2
         // @@ Hm, it's a bit fuzzy why we would be updating-for-install
         //    something outside of any project..?
         //
-        rs.global_scope ().insert_rule<mtime_target> (
-          perform_install_id, "install.file", fr);
+        scope& gs (rs.global_scope ());
 
-        rs.global_scope ().insert_rule<mtime_target> (
-          perform_uninstall_id, "uninstall.file", fr);
+        gs.insert_rule<mtime_target> (perform_install_id,   "install.file", fr);
+        gs.insert_rule<mtime_target> (perform_uninstall_id, "install.file", fr);
       }
 
       // Configuration.
diff --git a/libbuild2/install/rule.cxx b/libbuild2/install/rule.cxx
index 468fcc3..0a1b994 100644
--- a/libbuild2/install/rule.cxx
+++ b/libbuild2/install/rule.cxx
@@ -53,7 +53,7 @@ namespace build2
     const alias_rule alias_rule::instance;
 
     bool alias_rule::
-    match (action, target&, const string&) const
+    match (action, target&) const
     {
       // We always match.
       //
@@ -168,7 +168,7 @@ namespace build2
     const fsdir_rule fsdir_rule::instance;
 
     bool fsdir_rule::
-    match (action, target&, const string&) const
+    match (action, target&) const
     {
       // We always match.
       //
@@ -203,10 +203,10 @@ namespace build2
     const group_rule group_rule::instance (false /* see_through_only */);
 
     bool group_rule::
-    match (action a, target& t, const string& h) const
+    match (action a, target& t) const
     {
-      return (!see_through || t.type ().see_through) &&
-        alias_rule::match (a, t, h);
+      return (!see_through_only || t.type ().see_through ()) &&
+        alias_rule::match (a, t);
     }
 
     const target* group_rule::
@@ -300,7 +300,7 @@ namespace build2
     const file_rule file_rule::instance;
 
     bool file_rule::
-    match (action, target&, const string&) const
+    match (action, target&) const
     {
       // We always match, even if this target is not installable (so that we
       // can ignore it; see apply()).
diff --git a/libbuild2/install/rule.hxx b/libbuild2/install/rule.hxx
index 79cef85..ad9d6e7 100644
--- a/libbuild2/install/rule.hxx
+++ b/libbuild2/install/rule.hxx
@@ -22,7 +22,7 @@ namespace build2
     {
     public:
       virtual bool
-      match (action, target&, const string&) const override;
+      match (action, target&) const override;
 
       // Return NULL if this prerequisite should be ignored and pointer to its
       // target otherwise.
@@ -54,7 +54,7 @@ namespace build2
     {
     public:
       virtual bool
-      match (action, target&, const string&) const override;
+      match (action, target&) const override;
 
       virtual recipe
       apply (action, target&) const override;
@@ -78,7 +78,7 @@ namespace build2
     {
     public:
       virtual bool
-      match (action, target&, const string&) const override;
+      match (action, target&) const override;
 
       // Return NULL if this group member should be ignored and pointer to its
       // target otherwise.
@@ -103,10 +103,10 @@ namespace build2
       virtual recipe
       apply (action, target&) const override;
 
-      group_rule (bool see_through_only): see_through (see_through_only) {}
+      group_rule (bool sto): see_through_only (sto) {}
       static const group_rule instance;
 
-      bool see_through;
+      bool see_through_only;
     };
 
     struct install_dir;
@@ -115,7 +115,7 @@ namespace build2
     {
     public:
       virtual bool
-      match (action, target&, const string&) const override;
+      match (action, target&) const override;
 
       // Return NULL if this prerequisite should be ignored and pointer to its
       // target otherwise.