Use the previous approach for finding generator's match rank, now

that we have a use case. Add an explanation in code. More details
will be posted to the list.


[SVN r18475]

new/generators.jam

@@ -217,15 +217,20 @@ rule generator (
         if $(property-requirements) in $(properties-to-match) 
            && $(feature-requirements) in $(properties-to-match:G)
         {
-            # We're only used to rank matches based on the number of
-            # optional properties that appear in the property set.  
-            
-            # That seemed a little weak to me, so I changed it: now we
-            # account for the number of properties and features that
-            # were matched as well.  -- dwa 5/6/2003
+            # We only count matched optional properties to achive better
+            # orthogonality:
+            # - required properties are what is needed to generators to run
+            # - optional properties are used to resolve ambiguities
+            #
+            # For example, we have two generators
+            # - CPP->OBJ, with required property <toolset>msvc
+            # - RC->OBJ, without required properties
+            #
+            # If we could required properties, then the first one will be
+            # considered more specific, and the second one will never be
+            # tried.
             return 
               [ sequence.length
-                  $(all-requirements)
                   [ set.intersection 
                       [ optional-properties ] 
                     : $(properties-to-match)

test/custom_generator.py

@@ -0,0 +1,61 @@
+#!/usr/bin/python
+
+#  Copyright (C) Vladimir Prus 2003. Permission to copy, use, modify, sell and
+#  distribute this software is granted provided this copyright notice appears in
+#  all copies. This software is provided "as is" without express or implied
+#  warranty, and with no claim as to its suitability for any purpose.
+
+
+from BoostBuild import Tester, List
+
+
+t = Tester()
+
+# Attempt to declare a generator for creating OBJ from RC files.
+# That generator should be considered together with standard
+# CPP->OBJ generators and successfully create the target.
+# Since we don't have RC compiler everywhere, we fake the action.
+# The resulting OBJ will be unusable, but it must be created.
+
+t.write("project-root.jam", """ 
+import rc ; 
+""")
+
+t.write("rc.jam", """ 
+import type ;
+import generators ;
+import print ;
+
+type.register RC : rc ;
+
+rule resource-compile ( targets * : sources * : properties * )
+{
+    print.output $(targets[1]) ;
+    print.text "rc-object" ;
+}
+
+generators.register-standard rc.resource-compile : RC : OBJ ;
+
+""")
+
+t.write("Jamfile", """ 
+exe hello : hello.cpp r.rc ; 
+""")
+
+t.write("hello.cpp", """ 
+int main()
+{
+    return 0;
+} 
+""")
+
+t.write("r.rc", """ 
+""")
+
+t.run_build_system(status=1, stderr=None)
+t.expect_content("bin/$toolset/debug/r.obj", "rc-object\n")
+
+t.cleanup()
+
+
+

test/test_all.py

@@ -94,6 +94,7 @@ tests = [ "project_test1",
           "explicit",
           "absolute_sources",
           "dependency_property",
+          "custom_generator",
 	  ]
 
 if os.name == 'posix':

v2/build/generators.jam

@@ -217,15 +217,20 @@ rule generator (
         if $(property-requirements) in $(properties-to-match) 
            && $(feature-requirements) in $(properties-to-match:G)
         {
-            # We're only used to rank matches based on the number of
-            # optional properties that appear in the property set.  
-            
-            # That seemed a little weak to me, so I changed it: now we
-            # account for the number of properties and features that
-            # were matched as well.  -- dwa 5/6/2003
+            # We only count matched optional properties to achive better
+            # orthogonality:
+            # - required properties are what is needed to generators to run
+            # - optional properties are used to resolve ambiguities
+            #
+            # For example, we have two generators
+            # - CPP->OBJ, with required property <toolset>msvc
+            # - RC->OBJ, without required properties
+            #
+            # If we could required properties, then the first one will be
+            # considered more specific, and the second one will never be
+            # tried.
             return 
               [ sequence.length
-                  $(all-requirements)
                   [ set.intersection 
                       [ optional-properties ] 
                     : $(properties-to-match)

v2/test/custom_generator.py

@@ -0,0 +1,61 @@
+#!/usr/bin/python
+
+#  Copyright (C) Vladimir Prus 2003. Permission to copy, use, modify, sell and
+#  distribute this software is granted provided this copyright notice appears in
+#  all copies. This software is provided "as is" without express or implied
+#  warranty, and with no claim as to its suitability for any purpose.
+
+
+from BoostBuild import Tester, List
+
+
+t = Tester()
+
+# Attempt to declare a generator for creating OBJ from RC files.
+# That generator should be considered together with standard
+# CPP->OBJ generators and successfully create the target.
+# Since we don't have RC compiler everywhere, we fake the action.
+# The resulting OBJ will be unusable, but it must be created.
+
+t.write("project-root.jam", """ 
+import rc ; 
+""")
+
+t.write("rc.jam", """ 
+import type ;
+import generators ;
+import print ;
+
+type.register RC : rc ;
+
+rule resource-compile ( targets * : sources * : properties * )
+{
+    print.output $(targets[1]) ;
+    print.text "rc-object" ;
+}
+
+generators.register-standard rc.resource-compile : RC : OBJ ;
+
+""")
+
+t.write("Jamfile", """ 
+exe hello : hello.cpp r.rc ; 
+""")
+
+t.write("hello.cpp", """ 
+int main()
+{
+    return 0;
+} 
+""")
+
+t.write("r.rc", """ 
+""")
+
+t.run_build_system(status=1, stderr=None)
+t.expect_content("bin/$toolset/debug/r.obj", "rc-object\n")
+
+t.cleanup()
+
+
+

v2/test/test_all.py

@@ -94,6 +94,7 @@ tests = [ "project_test1",
           "explicit",
           "absolute_sources",
           "dependency_property",
+          "custom_generator",
 	  ]
 
 if os.name == 'posix':