Bug 863091 - Make auto clobbering opt-in rather than opt-out; r=glandium

To avoid surprises for devs building locally, auto clobbering is now opt-in, via
the use of |mk_add_options AUTOCLOBBER=1| in the mozconfig. Our automation uses
build/mozconfig.common which specifies this, so auto clobber will remain enabled
for our buildbot machines.

build/mozconfig.common

@@ -9,3 +9,5 @@
 # architectures, though note that if you want to override options set in
 # another mozconfig file, you'll need to use mozconfig.common.override instead
 # of this file.
+
+mk_add_options AUTOCLOBBER=1

client.mk

@@ -108,8 +108,8 @@ endef
 # before evaluation.
 $(eval $(subst ||,$(CR),$(shell _PYMAKE=$(.PYMAKE) $(TOPSRCDIR)/$(MOZCONFIG_LOADER) $(TOPSRCDIR) 2> $(TOPSRCDIR)/.mozconfig.out | sed 's/$$/||/')))
 
-ifdef NO_AUTOCLOBBER
-export NO_AUTOCLOBBER=1
+ifdef AUTOCLOBBER
+export AUTOCLOBBER=1
 endif
 
 # Automatically add -jN to make flags if not defined. N defaults to number of cores.

python/mozbuild/mozbuild/controller/clobber.py

@@ -97,7 +97,7 @@ class Clobberer(object):
             with open(self.obj_clobber, 'a'):
                 pass
 
-    def maybe_do_clobber(self, cwd, allow_auto=True, fh=sys.stderr):
+    def maybe_do_clobber(self, cwd, allow_auto=False, fh=sys.stderr):
         """Perform a clobber if it is required. Maybe.
 
         This is the API the build system invokes to determine if a clobber
@@ -120,15 +120,15 @@ class Clobberer(object):
             return False, False, None
 
         # So a clobber is needed. We only perform a clobber if we are
-        # allowed to perform an automatic clobber (the default) and if the
+        # allowed to perform an automatic clobber (off by default) and if the
         # current directory is not under the object directory. The latter is
         # because operating systems, filesystems, and shell can throw fits
         # if the current working directory is deleted from under you. While it
         # can work in some scenarios, we take the conservative approach and
         # never try.
         if not allow_auto:
-            return True, False, self._message(
-                'Automatic clobbering has been disabled.')
+            return True, False, self._message('Automatic clobbering is not '
+                'enabled (add "mk_add_options AUTOCLOBBER=1" to your mozconfig).')
 
         if cwd.startswith(self.topobjdir) and cwd != self.topobjdir:
             return True, False, self._message(
@@ -175,7 +175,7 @@ def main(args, env, cwd, fh=sys.stderr):
     if not os.path.isabs(topobjdir):
         topobjdir = os.path.abspath(topobjdir)
 
-    auto = False if env.get('NO_AUTOCLOBBER', False) else True
+    auto = True if env.get('AUTOCLOBBER', False) else False
     clobber = Clobberer(topsrcdir, topobjdir)
     required, performed, message = clobber.maybe_do_clobber(cwd, auto, fh)
 

python/mozbuild/mozbuild/test/controller/test_clobber.py

@@ -52,7 +52,7 @@ class TestClobberer(unittest.TestCase):
         self.assertFalse(c.clobber_needed())
 
         # Side-effect is topobjdir is created with CLOBBER file touched.
-        required, performed, reason = c.maybe_do_clobber(os.getcwd())
+        required, performed, reason = c.maybe_do_clobber(os.getcwd(), True)
         self.assertFalse(required)
         self.assertFalse(performed)
         self.assertIsNone(reason)
@@ -66,7 +66,7 @@ class TestClobberer(unittest.TestCase):
         c = Clobberer(self.get_topsrcdir(), self.get_tempdir())
         self.assertFalse(c.clobber_needed())
 
-        required, performed, reason = c.maybe_do_clobber(os.getcwd())
+        required, performed, reason = c.maybe_do_clobber(os.getcwd(), True)
         self.assertFalse(required)
         self.assertFalse(performed)
         self.assertIsNone(reason)
@@ -80,7 +80,7 @@ class TestClobberer(unittest.TestCase):
         with open(c.obj_clobber, 'a'):
             pass
 
-        required, performed, reason = c.maybe_do_clobber(os.getcwd())
+        required, performed, reason = c.maybe_do_clobber(os.getcwd(), True)
         self.assertFalse(required)
         self.assertFalse(performed)
         self.assertIsNone(reason)
@@ -103,13 +103,7 @@ class TestClobberer(unittest.TestCase):
 
         self.assertTrue(c.clobber_needed())
 
-        required, performed, reason = c.maybe_do_clobber(os.getcwd(), False)
-        self.assertTrue(required)
-        self.assertFalse(performed)
-        self.assertIn('Automatic clobbering has been disabled', reason)
-
-        # Now let's actually do it.
-        required, performed, reason = c.maybe_do_clobber(os.getcwd())
+        required, performed, reason = c.maybe_do_clobber(os.getcwd(), True)
         self.assertTrue(required)
         self.assertTrue(performed)
 
@@ -148,7 +142,7 @@ class TestClobberer(unittest.TestCase):
 
         self.assertTrue(c.clobber_needed())
 
-        required, performed, reason = c.maybe_do_clobber(c.topobjdir)
+        required, performed, reason = c.maybe_do_clobber(c.topobjdir, True)
         self.assertTrue(required)
         self.assertTrue(performed)
 
@@ -169,14 +163,14 @@ class TestClobberer(unittest.TestCase):
         d = os.path.join(c.topobjdir, 'dummy_dir')
         os.mkdir(d)
 
-        required, performed, reason = c.maybe_do_clobber(d)
+        required, performed, reason = c.maybe_do_clobber(d, True)
         self.assertTrue(required)
         self.assertFalse(performed)
         self.assertIn('Cannot clobber while the shell is inside', reason)
 
 
-    def test_mozconfig_overrides_auto_clobber(self):
-        """If NO_AUTOCLOBBER is in the environment, don't auto clobber."""
+    def test_mozconfig_opt_in(self):
+        """Auto clobber iff AUTOCLOBBER is in the environment."""
 
         topsrcdir = self.get_topsrcdir()
         topobjdir = self.get_tempdir()
@@ -194,15 +188,26 @@ class TestClobberer(unittest.TestCase):
         old_time = os.path.getmtime(os.path.join(topsrcdir, 'CLOBBER')) - 60
         os.utime(obj_clobber, (old_time, old_time))
 
+        # Check auto clobber is off by default
         env = dict(os.environ)
-        env['NO_AUTOCLOBBER'] = '1'
+        if env.get('AUTOCLOBBER', False):
+            del env['AUTOCLOBBER']
 
         s = StringIO()
         status = clobber([topsrcdir, topobjdir], env, os.getcwd(), s)
         self.assertEqual(status, 1)
-        self.assertIn('Automatic clobbering has been disabled', s.getvalue())
+        self.assertIn('Automatic clobbering is not enabled', s.getvalue())
         self.assertTrue(os.path.exists(dummy_file))
 
+        # Check auto clobber opt-in works
+        env['AUTOCLOBBER'] = '1'
+
+        s = StringIO()
+        status = clobber([topsrcdir, topobjdir], env, os.getcwd(), s)
+        self.assertEqual(status, 1)
+        self.assertIn('Successfully completed auto clobber', s.getvalue())
+        self.assertFalse(os.path.exists(dummy_file))
+
 
 if __name__ == '__main__':
     main()