Bug 861453 - Restore empty substs after bug 857557, but put them in a separate file, unlisted as a dependency for everything. r=gps

config/autoconf.mk.in

@@ -1,2 +1,3 @@
+include $(DEPTH)/config/emptyvars.mk
 @ALLSUBSTS@
 include $(topsrcdir)/config/baseconfig.mk

config/emptyvars.mk.in

@@ -0,0 +1 @@
+@ALLEMPTYSUBSTS@

config/moz.build

@@ -6,6 +6,7 @@
 
 CONFIGURE_SUBST_FILES += [
     'autoconf.mk',
+    'emptyvars.mk',
     'doxygen.cfg',
     'makefiles/test/Makefile',
     'tests/makefiles/autodeps/Makefile',

js/src/config/autoconf.mk.in

@@ -1,2 +1,3 @@
+include $(DEPTH)/config/emptyvars.mk
 @ALLSUBSTS@
 include $(topsrcdir)/config/baseconfig.mk

js/src/config/emptyvars.mk.in

@@ -0,0 +1 @@
+@ALLEMPTYSUBSTS@

js/src/configure.in

@@ -4384,7 +4384,7 @@ AC_SUBST(ac_configure_args)
 dnl Spit out some output
 dnl ========================================================
 
-AC_OUTPUT([js-confdefs.h Makefile config/autoconf.mk])
+AC_OUTPUT([js-confdefs.h Makefile config/autoconf.mk config/emptyvars.mk])
 
 # Produce the js-config script at configure time; see the comments for
 # 'js-config' in Makefile.in.

python/mozbuild/mozbuild/backend/configenvironment.py

@@ -86,13 +86,15 @@ class ConfigEnvironment(object):
       - ALLDEFINES contains the defines in the form #define NAME VALUE, in
         sorted order, for use in config files, for an automatic listing of
         defines.
-    and another additional subst variable from all the other substs:
+    and two other additional subst variables from all the other substs:
       - ALLSUBSTS contains the substs in the form NAME = VALUE, in sorted
         order, for use in autoconf.mk. It includes ACDEFINES, but doesn't
         include ALLDEFINES. Only substs with a VALUE are included, such that
         the resulting file doesn't change when new empty substs are added.
         This results in less invalidation of build dependencies in the case
         of autoconf.mk..
+      - ALLEMPTYSUBSTS contains the substs with an empty value, in the form
+        NAME =.
 
     ConfigEnvironment expects a "top_srcdir" subst to be set with the top
     source directory, in msys format on windows. It is used to derive a
@@ -113,6 +115,8 @@ class ConfigEnvironment(object):
             shell_escape(self.defines[name])) for name in global_defines])
         self.substs['ALLSUBSTS'] = '\n'.join(sorted(['%s = %s' % (name,
             self.substs[name]) for name in self.substs if self.substs[name]]))
+        self.substs['ALLEMPTYSUBSTS'] = '\n'.join(sorted(['%s =' % name
+            for name in self.substs if not self.substs[name]]))
         self.substs['ALLDEFINES'] = '\n'.join(sorted(['#define %s %s' % (name,
             self.defines[name]) for name in global_defines]))
 

python/mozbuild/mozbuild/test/backend/test_configenvironment.py

@@ -22,14 +22,14 @@ class ConfigEnvironment(ConfigStatus.ConfigEnvironment):
 
 class TestEnvironment(unittest.TestCase):
     def test_auto_substs(self):
-        '''Test the automatically set values of ACDEFINES, ALLDEFINES
-        and ALLSUBSTS.
+        '''Test the automatically set values of ACDEFINES, ALLDEFINES,
+        ALLSUBSTS and ALLEMPTYSUBSTS.
         '''
         env = ConfigEnvironment('.', '.',
                   defines = [ ('foo', 'bar'), ('baz', 'qux 42'),
                               ('abc', 'def'), ('extra', 'foobar') ],
                   non_global_defines = ['extra', 'ignore'],
-                  substs = [ ('FOO', 'bar'), ('ABC', 'def'),
+                  substs = [ ('FOO', 'bar'), ('FOOBAR', ''), ('ABC', 'def'),
                              ('bar', 'baz qux'), ('zzz', '"abc def"'),
                              ('qux', '') ])
         # non_global_defines should be filtered out in ACDEFINES and
@@ -47,6 +47,9 @@ ACDEFINES = -Dfoo=bar -Dbaz=qux\ 42 -Dabc=def
 FOO = bar
 bar = baz qux
 zzz = "abc def"''')
+        # ALLEMPTYSUBSTS contains all substs with no value.
+        self.assertEqual(env.substs['ALLEMPTYSUBSTS'], '''FOOBAR =
+qux =''')
 
     def test_config_file(self):
         '''Test the creation of config files.