From 10604d850510e46b2ee625548abe5eb9a1172a0d Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 21 Jul 2015 09:39:57 +0200
Subject: Add alias{} target type, use as base for dir{}

---
 build/context.cxx |  9 +++++----
 build/rule        |  2 +-
 build/rule.cxx    |  6 +++---
 build/target      | 21 +++++++++++++++++----
 build/target.cxx  | 18 ++++++++++++++----
 5 files changed, 40 insertions(+), 16 deletions(-)

(limited to 'build')

diff --git a/build/context.cxx b/build/context.cxx
index bd6143a..9b22478 100644
--- a/build/context.cxx
+++ b/build/context.cxx
@@ -30,7 +30,7 @@ namespace build
 
   // Builtin rules.
   //
-  static dir_rule dir_;
+  static alias_rule alias_;
   static fsdir_rule fsdir_;
   static file_rule file_;
 
@@ -67,6 +67,7 @@ namespace build
       target_type_map& tts (global_scope->target_types);
 
       tts.insert<file>  ();
+      tts.insert<alias> ();
       tts.insert<dir>   ();
       tts.insert<fsdir> ();
     }
@@ -76,9 +77,9 @@ namespace build
     {
       rule_map& rs (global_scope->rules);
 
-      rs.insert<dir> (default_id, "dir", dir_);
-      rs.insert<dir> (update_id, "dir", dir_);
-      rs.insert<dir> (clean_id, "dir", dir_);
+      rs.insert<alias> (default_id, "alias", alias_);
+      rs.insert<alias> (update_id, "alias", alias_);
+      rs.insert<alias> (clean_id, "alias", alias_);
 
       rs.insert<fsdir> (default_id, "fsdir", fsdir_);
       rs.insert<fsdir> (update_id, "fsdir", fsdir_);
diff --git a/build/rule b/build/rule
index fbcf06b..5b0149b 100644
--- a/build/rule
+++ b/build/rule
@@ -67,7 +67,7 @@ namespace build
     perform_update (action, target&);
   };
 
-  class dir_rule: public rule
+  class alias_rule: public rule
   {
   public:
     virtual match_result
diff --git a/build/rule.cxx b/build/rule.cxx
index 6db0f4f..03c86c8 100644
--- a/build/rule.cxx
+++ b/build/rule.cxx
@@ -133,15 +133,15 @@ namespace build
     return target_state::unchanged;
   }
 
-  // dir_rule
+  // alias_rule
   //
-  match_result dir_rule::
+  match_result alias_rule::
   match (action, target& t, const string&) const
   {
     return t;
   }
 
-  recipe dir_rule::
+  recipe alias_rule::
   apply (action a, target& t, const match_result&) const
   {
     search_and_match_prerequisites (a, t);
diff --git a/build/target b/build/target
index d164f72..e07f6e0 100644
--- a/build/target
+++ b/build/target
@@ -889,11 +889,10 @@ namespace build
     static const target_type static_type;
   };
 
-  // Directory alias/action target. Note that it is not mtime-based.
-  // Rather it is meant to represent a group of targets. For actual
-  // filesystem directory (creation), see fsdir.
+  // Alias target. It represents a list of targets (its prerequisites)
+  // as a single "name".
   //
-  class dir: public target
+  class alias: public target
   {
   public:
     using target::target;
@@ -903,6 +902,20 @@ namespace build
     static const target_type static_type;
   };
 
+  // Directory target. Note that this is not a filesystem directory
+  // but rather an alias target with the directory name. For actual
+  // filesystem directory (creation), see fsdir.
+  //
+  class dir: public alias
+  {
+  public:
+    using alias::alias;
+
+  public:
+    virtual const target_type& type () const {return static_type;}
+    static const target_type static_type;
+  };
+
   // While a filesystem directory is mtime-based, the semantics is
   // not very useful in our case. In particular, if another target
   // depends on fsdir{}, then all that's desired is the creation of
diff --git a/build/target.cxx b/build/target.cxx
index 63bb2fe..f9662fa 100644
--- a/build/target.cxx
+++ b/build/target.cxx
@@ -297,9 +297,8 @@ namespace build
   static target*
   search_alias (const prerequisite_key& pk)
   {
-    // For an alias/action we don't want to silently create a target
-    // since it will do nothing and it most likely not what the author
-    // intended.
+    // For an alias we don't want to silently create a target since it
+    // will do nothing and it most likely not what the user intended.
     //
     target* t (search_existing_target (pk));
 
@@ -368,11 +367,22 @@ namespace build
     false
   };
 
+  const target_type alias::static_type
+  {
+    typeid (alias),
+    "alias",
+    &target::static_type,
+    &target_factory<alias>,
+    nullptr, // Should never need.
+    &search_alias,
+    false
+  };
+
   const target_type dir::static_type
   {
     typeid (dir),
     "dir",
-    &target::static_type,
+    &alias::static_type,
     &target_factory<dir>,
     nullptr, // Should never need.
     &search_alias,
-- 
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