Implement noop meta-operation

The effect is loading all the buildfiles but not searching/matching/executing
any targets/operations. Useful for testing.

5 files changed, 33 insertions, 12 deletions

diff --git a/build2/b.cxx b/build2/b.cxx
index a652c97..4a764e6 100644
--- a/build2/b.cxx
+++ b/build2/b.cxx
@@ -927,15 +927,16 @@ main (int argc, char* argv[])
           // building before we know how to for all the targets in this
           // operation batch.
           //
-          {
-            scope& bs (scopes.find (ts.out_base));
+          scope& bs (scopes.find (ts.out_base));
 
-            const string* e;
-            const target_type* ti (bs.find_target_type (tn, e));
+          const string* e;
+          const target_type* ti (bs.find_target_type (tn, e));
 
-            if (ti == nullptr)
-              fail (l) << "unknown target type " << tn.type;
+          if (ti == nullptr)
+            fail (l) << "unknown target type " << tn.type;
 
+          if (mif->search != nullptr)
+          {
             // If the directory is relative, assume it is relative to work
             // (must be consistent with how we derived out_base above).
             //
@@ -986,8 +987,8 @@ main (int argc, char* argv[])
 
         action a (mid, oid, 0);
 
-        mif->match (a, tgs);
-        mif->execute (a, tgs, verb == 0);
+        if (mif->match != nullptr)   mif->match (a, tgs);
+        if (mif->execute != nullptr) mif->execute (a, tgs, verb == 0);
 
         if (post_oid != 0)
         {
diff --git a/build2/context.cxx b/build2/context.cxx
index 03e64cd..3b58b90 100644
--- a/build2/context.cxx
+++ b/build2/context.cxx
@@ -66,6 +66,7 @@ namespace build2
     // constants in <build2/operation>.
     //
     meta_operation_table.clear ();
+    meta_operation_table.insert ("noop");
     meta_operation_table.insert ("perform");
     meta_operation_table.insert ("configure");
     meta_operation_table.insert ("disfigure");
diff --git a/build2/file.cxx b/build2/file.cxx
index 478722f..ce9571d 100644
--- a/build2/file.cxx
+++ b/build2/file.cxx
@@ -154,6 +154,7 @@ namespace build2
     //
     if (first)
     {
+      rs.meta_operations.insert (noop_id, noop);
       rs.meta_operations.insert (perform_id, perform);
 
       rs.operations.insert (default_id, default_);
diff --git a/build2/operation b/build2/operation
index 730a958..e04d1a3 100644
--- a/build2/operation
+++ b/build2/operation
@@ -99,10 +99,11 @@ namespace build2
 
   // Id constants for build-in and pre-defined meta/operations.
   //
-  const meta_operation_id perform_id   = 1;
-  const meta_operation_id configure_id = 2;
-  const meta_operation_id disfigure_id = 3;
-  const meta_operation_id dist_id = 4;
+  const meta_operation_id noop_id      = 1; // nomop?
+  const meta_operation_id perform_id   = 2;
+  const meta_operation_id configure_id = 3;
+  const meta_operation_id disfigure_id = 4;
+  const meta_operation_id dist_id      = 5;
 
   // The default operation is a special marker that can be used to indicate
   // that no operation was explicitly specified by the user. If adding
@@ -250,6 +251,7 @@ namespace build2
   void
   execute (action, const action_targets&, bool quiet);
 
+  extern meta_operation_info noop;
   extern meta_operation_info perform;
 
   // Operation info.
diff --git a/build2/operation.cxx b/build2/operation.cxx
index f8ce46f..57ad84b 100644
--- a/build2/operation.cxx
+++ b/build2/operation.cxx
@@ -170,6 +170,22 @@ namespace build2
     }
   }
 
+  meta_operation_info noop {
+    noop_id,
+    "noop",
+    "",      // Presumably we will never need these since we are not going
+    "",      // to do anything.
+    "",
+    nullptr, // meta-operation pre
+    nullptr, // operation pre
+    &load,
+    nullptr, // search
+    nullptr, // match
+    nullptr, // execute
+    nullptr, // operation post
+    nullptr  // meta-operation post
+  };
+
   meta_operation_info perform {
     perform_id,
     "perform",