Fix error code propagation in 'mb gen'.

tools/mb/mb_unittest.py

Index: tools/mb/mb_unittest.py
diff --git a/tools/mb/mb_unittest.py b/tools/mb/mb_unittest.py
index efb453c26845840c09989f5ce3153b0e223676be..ac822ab49746e9c3da6475ce1985cb7793f44502 100644
--- a/tools/mb/mb_unittest.py
+++ b/tools/mb/mb_unittest.py
@@ -100,12 +100,12 @@ TEST_CONFIG = """\
 
 
 class UnitTest(unittest.TestCase):
-  def fake_mbw(self, files):
+  def fake_mbw(self, files=None):
     mbw = FakeMBW()
+    mbw.files.setdefault(mbw.default_config, TEST_CONFIG)

[Dirk Pranke, 2015/04/24 20:38:52]

these diffs are unrelated to the fix, but clean up the api a bit.

     if files:
       for path, contents in files.items():
         mbw.files[path] = contents
-    mbw.files.setdefault(mbw.default_config, TEST_CONFIG)
     return mbw
 
   def check(self, args, mbw=None, files=None, out=None, err=None, ret=None):
@@ -180,6 +180,12 @@ class UnitTest(unittest.TestCase):
     self.check(['gen', '-c', 'gn_debug', '//out/Default'], ret=0)
     self.check(['gen', '-c', 'gyp_rel_bot', '//out/Release'], ret=0)
 
+  def test_gen_fails(self):
+    mbw = self.fake_mbw()
+    mbw.Call = lambda cmd: (1, '', '')
+    self.check(['gen', '-c', 'gn_debug', '//out/Default'], mbw=mbw, ret=1)
+    self.check(['gen', '-c', 'gyp_rel_bot', '//out/Release'], mbw=mbw, ret=1)
+
   def test_goma_dir_expansion(self):
     self.check(['lookup', '-c', 'gyp_rel_bot', '-g', '/foo'], ret=0,
                out=("python build/gyp_chromium -G 'output_dir=<path>' "