Bug 900526, part 1: Allow inheritable moz.build variables, r=gps.

python/mozbuild/mozbuild/frontend/reader.py

@@ -181,6 +181,10 @@ class MozbuildSandbox(Sandbox):
             for name, func in FUNCTIONS.items():
                 d[name] = getattr(self, func[0])
 
+        # Initialize the exports that we need in the global.
+        extra_vars = self.metadata.get('exports', dict())
+        self._globals.update(extra_vars)
+
     def exec_file(self, path, filesystem_absolute=False):
         """Override exec_file to normalize paths and restrict file loading.
 
@@ -242,6 +246,30 @@ class MozbuildSandbox(Sandbox):
 
             self['TIERS'][tier][key].append(path)
 
+    def _export(self, varname):
+        """Export the variable to all subdirectories of the current path."""
+
+        exports = self.metadata.setdefault('exports', dict())
+        if varname in exports:
+            raise Exception('Variable has already been exported: %s' % varname)
+
+        try:
+            # Doing a regular self._globals[varname] causes a set as a side
+            # effect. By calling the dict method instead, we don't have any
+            # side effects.
+            exports[varname] = dict.__getitem__(self._globals, varname)
+        except KeyError:
+            self.last_name_error = KeyError('global_ns', 'get_unknown', varname)
+            raise self.last_name_error
+
+    def recompute_exports(self):
+        """Recompute the variables to export to subdirectories with the current
+        values in the subdirectory."""
+
+        if 'exports' in self.metadata:
+            for key in self.metadata['exports']:
+                self.metadata['exports'][key] = self[key]
+
     def _include(self, path):
         """Include and exec another file within the context of this one."""
 
@@ -680,6 +708,9 @@ class BuildReader(object):
                 recurse_info[d] = {'tier': metadata.get('tier', None),
                                    'parent': sandbox['RELATIVEDIR'],
                                    'var': var}
+                if 'exports' in sandbox.metadata:
+                    sandbox.recompute_exports()
+                    recurse_info[d]['exports'] = sandbox.metadata['exports']
 
         # We also have tiers whose members are directories.
         if 'TIERS' in sandbox:

python/mozbuild/mozbuild/frontend/sandbox_symbols.py

@@ -575,6 +575,34 @@ FUNCTIONS = {
            add_tier_dir('base', 'bar', external=True)
         """),
 
+    'export': ('_export', (str,),
+        """Make the specified variable available to all child directories.
+
+        The variable specified by the argument string is added to the
+        environment of all directories specified in the DIRS, PARALLEL_DIRS,
+        TOOL_DIRS, TEST_DIRS, and TEST_TOOL_DIRS variables. If those directories
+        themselves have child directories, the variable will be exported to all
+        of them.
+
+        The value used for the variable is the final value at the end of the
+        moz.build file, so it is possible (but not recommended style) to place
+        the export before the definition of the variable.
+
+        This function is limited to the upper-case variables that have special
+        meaning in moz.build files.
+
+        NOTE: Please consult with a build peer before adding a new use of this
+        function.
+
+        Example usage
+        ^^^^^^^^^^^^^
+
+        To make all children directories install as the given extension::
+
+          XPI_NAME = 'cool-extension'
+          export('XPI_NAME')
+        """),
+
     'warning': ('_warning', (str,),
         """Issue a warning.
 

python/mozbuild/mozbuild/test/frontend/data/inheriting-variables/bar/moz.build

@@ -0,0 +1,7 @@
+# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+XPIDL_MODULE = 'bazbar'

python/mozbuild/mozbuild/test/frontend/data/inheriting-variables/foo/baz/moz.build

@@ -0,0 +1,5 @@
+# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.

python/mozbuild/mozbuild/test/frontend/data/inheriting-variables/foo/moz.build

@@ -0,0 +1,7 @@
+# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIRS += ['baz']

python/mozbuild/mozbuild/test/frontend/data/inheriting-variables/moz.build

@@ -0,0 +1,10 @@
+# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+XPIDL_MODULE = 'foobar'
+export("XPIDL_MODULE")
+
+DIRS += ['foo', 'bar']

python/mozbuild/mozbuild/test/frontend/test_reader.py

@@ -253,5 +253,16 @@ class TestBuildReader(unittest.TestCase):
         e = bre.exception
         self.assertIn('The DIRS variable is not allowed in such directories.', str(e))
 
+    def test_inheriting_variables(self):
+        reader = self.reader('inheriting-variables')
+
+        sandboxes = list(reader.read_topsrcdir())
+
+        self.assertEqual(len(sandboxes), 4)
+        self.assertEqual([sandbox['RELATIVEDIR'] for sandbox in sandboxes],
+            ['', 'foo', 'foo/baz', 'bar'])
+        self.assertEqual([sandbox['XPIDL_MODULE'] for sandbox in sandboxes],
+            ['foobar', 'foobar', 'foobar', 'bazbar'])
+
 if __name__ == '__main__':
     main()