Bug 946175 - Forbid assigning over a value previously set in moz.build. r=gps

netwerk/wifi/moz.build

@@ -4,8 +4,6 @@
 # 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/.
 
-FAIL_ON_WARNINGS = True
-
 XPIDL_SOURCES += [
     'nsIWifiAccessPoint.idl',
     'nsIWifiListener.idl',
@@ -27,9 +25,10 @@ else:
         'nsWifiMonitor.cpp',
     ]
 
-if CONFIG['OS_ARCH'] == 'Darwin':
 # osx_corewlan.mm has warnings I don't understand.
-    FAIL_ON_WARNINGS = False
+FAIL_ON_WARNINGS = CONFIG['OS_ARCH'] != 'Darwin'
+
+if CONFIG['OS_ARCH'] == 'Darwin':
     UNIFIED_SOURCES += [
         'nsWifiScannerMac.cpp',
     ]

python/mozbuild/mozbuild/frontend/sandbox.py

@@ -124,6 +124,8 @@ class GlobalNamespace(dict):
 
         self._allow_all_writes = False
 
+        self._allow_one_mutation = set()
+
     def __getitem__(self, name):
         try:
             return dict.__getitem__(self, name)
@@ -151,8 +153,21 @@ class GlobalNamespace(dict):
     def __setitem__(self, name, value):
         if self._allow_all_writes:
             dict.__setitem__(self, name, value)
+            self._allow_one_mutation.add(name)
             return
 
+        # Forbid assigning over a previously set value. Interestingly, when
+        # doing FOO += ['bar'], python actually does something like:
+        #   foo = namespace.__getitem__('FOO')
+        #   foo.__iadd__(['bar'])
+        #   namespace.__setitem__('FOO', foo)
+        # This means __setitem__ is called with the value that is already
+        # in the dict, when doing +=, which is permitted.
+        if name in self._allow_one_mutation:
+            self._allow_one_mutation.remove(name)
+        elif name in self and dict.__getitem__(self, name) is not value:
+            raise Exception('Reassigning %s is forbidden' % name)
+
         # We don't need to check for name.isupper() here because LocalNamespace
         # only sends variables our way if isupper() is True.
         stored_type, input_type, docs, tier = \
@@ -195,6 +210,11 @@ class GlobalNamespace(dict):
         yield self
         self._allow_all_writes = False
 
+    # dict.update doesn't call our __setitem__, so we have to override it.
+    def update(self, other):
+        for name, value in other.items():
+            self.__setitem__(name, value)
+
 
 class LocalNamespace(dict):
     """Represents the locals namespace in a Sandbox.

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

@@ -3,5 +3,3 @@
 # 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/test_namespaces.py

@@ -76,10 +76,23 @@ class TestGlobalNamespace(unittest.TestCase):
             self.assertTrue(d['foo'])
 
         with self.assertRaises(KeyError) as ke:
-            ns['foo'] = False
+            ns['bar'] = False
 
         self.assertEqual(ke.exception.args[1], 'set_unknown')
 
+        ns['DIRS'] = []
+        with self.assertRaisesRegexp(Exception, 'Reassigning .* is forbidden') as ke:
+            ns['DIRS'] = []
+
+        with ns.allow_all_writes() as d:
+            d['DIST_SUBDIR'] = 'foo'
+
+        self.assertEqual(ns['DIST_SUBDIR'], 'foo')
+        ns['DIST_SUBDIR'] = 'bar'
+        self.assertEqual(ns['DIST_SUBDIR'], 'bar')
+        with self.assertRaisesRegexp(Exception, 'Reassigning .* is forbidden') as ke:
+            ns['DIST_SUBDIR'] = 'baz'
+
         self.assertTrue(d['foo'])
 
     def test_key_checking(self):

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

@@ -262,7 +262,7 @@ class TestBuildReader(unittest.TestCase):
         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'])
+            ['foobar', 'foobar', 'foobar', 'foobar'])
 
 if __name__ == '__main__':
     main()

python/mozbuild/mozbuild/test/frontend/test_sandbox.py

@@ -146,9 +146,9 @@ class TestSandbox(unittest.TestCase):
         sandbox = self.sandbox()
 
         sandbox.exec_source('DIRS = ["foo"]', 'foo.py')
-        sandbox.exec_source('DIRS = ["bar"]', 'foo.py')
+        sandbox.exec_source('DIRS += ["bar"]', 'foo.py')
 
-        self.assertEqual(sandbox['DIRS'], ['bar'])
+        self.assertEqual(sandbox['DIRS'], ['foo', 'bar'])
 
     def test_exec_source_illegal_key_set(self):
         sandbox = self.sandbox()

toolkit/components/diskspacewatcher/moz.build

@@ -13,7 +13,6 @@ EXPORTS += [
 ]
 
 XPIDL_MODULE = 'diskspacewatcher'
-XPIDL_MODULE = 'toolkitcomps'
 
 SOURCES = [
     'DiskSpaceWatcher.cpp',