Initial work for default update outer operation

While update still uses the old "all update rules update all their
prerequisites" assumption, test and install have been fixed not to
rely on this.

1 files changed, 23 insertions, 2 deletions

diff --git a/build2/rule.cxx b/build2/rule.cxx
index ef1d3a4..e215846 100644
--- a/build2/rule.cxx
+++ b/build2/rule.cxx
@@ -98,6 +98,11 @@ namespace build2
   recipe file_rule::
   apply (action a, target& t) const
   {
+    /*
+      @@ outer
+      return noop_recipe;
+    */
+
     // Update triggers the update of this target's prerequisites so it would
     // seem natural that we should also trigger their cleanup. However, this
     // possibility is rather theoretical so until we see a real use-case for
@@ -220,6 +225,8 @@ namespace build2
     // First update prerequisites (e.g. create parent directories) then create
     // this directory.
     //
+    // @@ outer: should we assume for simplicity its only prereqs are fsdir{}?
+    //
     if (!t.prerequisite_targets[a].empty ())
       ts = straight_execute_prerequisites (a, t);
 
@@ -232,6 +239,8 @@ namespace build2
     // better performance by first checking if it indeed exists. See
     // butl::try_mkdir() for details.
     //
+    // @@ Also skip prerequisites? Can't we return noop in apply?
+    //
     if (!exists (d) && fsdir_mkdir (t, d))
       ts |= target_state::changed;
 
@@ -280,7 +289,19 @@ namespace build2
 
   const fsdir_rule fsdir_rule::instance;
 
-  // fallback_rule
+  // noop_rule
   //
-  const fallback_rule fallback_rule::instance;
+  bool noop_rule::
+  match (action, target&, const string&) const
+  {
+    return true;
+  }
+
+  recipe noop_rule::
+  apply (action, target&) const
+  {
+    return noop_recipe;
+  }
+
+  const noop_rule noop_rule::instance;
 }