Bug 1297718 - Add config.status to sys.modules for dependency detection; r=glandium

MozReview-Commit-ID: J5WaTPYc0vJ

python/mozbuild/mozbuild/action/file_generate.py

@@ -61,18 +61,34 @@ def main(argv):
     try:
         with FileAvoidWrite(args.output_file) as output:
             ret = module.__dict__[method](output, *args.additional_arguments)
-            # We treat sets as a statement of success.  Everything else
-            # is an error (so scripts can conveniently |return 1| or
-            # similar).
-            if isinstance(ret, set) and ret:
-                ret |= set(iter_modules_in_path(buildconfig.topsrcdir,
-                                                buildconfig.topobjdir))
-                mk = Makefile()
-                mk.create_rule([args.output_file]).add_dependencies(ret)
-                with FileAvoidWrite(args.dep_file) as dep_file:
-                    mk.dump(dep_file)
+            # The following values indicate a statement of success:
+            #  - a set() (see below)
+            #  - 0
+            #  - False
+            #  - None
+            #
+            # Everything else is an error (so scripts can conveniently |return
+            # 1| or similar). If a set is returned, the elements of the set
+            # indicate additional dependencies that will be listed in the deps
+            # file. Python module imports are automatically included as
+            # dependencies.
+            if isinstance(ret, set):
+                deps = ret
                 # The script succeeded, so reset |ret| to indicate that.
                 ret = None
+            else:
+                deps = set()
+
+            # Only write out the dependencies if the script was successful
+            if not ret:
+                # Add dependencies on any python modules that were imported by
+                # the script.
+                deps |= set(iter_modules_in_path(buildconfig.topsrcdir,
+                                                 buildconfig.topobjdir))
+                mk = Makefile()
+                mk.create_rule([args.output_file]).add_dependencies(deps)
+                with FileAvoidWrite(args.dep_file) as dep_file:
+                    mk.dump(dep_file)
         # Even when our file's contents haven't changed, we want to update
         # the file's mtime so make knows this target isn't still older than
         # whatever prerequisite caused it to be built this time around.

python/mozbuild/mozbuild/backend/configenvironment.py

@@ -8,7 +8,7 @@ import os
 import sys
 
 from collections import Iterable
-from types import StringTypes
+from types import StringTypes, ModuleType
 
 import mozpack.path as mozpath
 
@@ -45,6 +45,12 @@ class BuildConfig(object):
         # cache the compiled code as it can be reused
         # we cache it the first time, or if the file changed
         if not path in code_cache or code_cache[path][0] != mtime:
+            # Add config.status manually to sys.modules so it gets picked up by
+            # iter_modules_in_path() for automatic dependencies.
+            mod = ModuleType('config.status')
+            mod.__file__ = path
+            sys.modules['config.status'] = mod
+
             with open(path, 'rt') as fh:
                 source = fh.read()
                 code_cache[path] = (