Explicitly specify the path to GN in mb.py.

Previously we were (a) assuming it was in the path and (b) not accounting
for it being called 'gn.exe' on windows.

TBR=phajdan.jr@chromium.org
BUG=454413
CQ_EXTRA_TRYBOTS=tryserver.chromium.mac:mac_chromium_gn_dbg

Review URL: https://codereview.chromium.org/1082353002

Cr-Commit-Position: refs/heads/master@{#325116}

2 files changed, 20 insertions, 8 deletions

diff --git a/tools/mb/mb.py b/tools/mb/mb.py
index 1b7bbb9..2a9941b 100755
--- a/tools/mb/mb.py
+++ b/tools/mb/mb.py
@@ -35,6 +35,7 @@ class MetaBuildWrapper(object):
     self.chromium_src_dir = p.normpath(d(d(d(p.abspath(__file__)))))
     self.default_config = p.join(self.chromium_src_dir, 'tools', 'mb',
                                  'mb_config.pyl')
+    self.platform = sys.platform
     self.args = argparse.Namespace()
     self.configs = {}
     self.masters = {}
@@ -131,7 +132,7 @@ class MetaBuildWrapper(object):
   def CmdLookup(self):
     vals = self.GetConfig()
     if vals['type'] == 'gn':
-      cmd = self.GNCmd('<path>', vals['gn_args'])
+      cmd = self.GNCmd('gen', '<path>', vals['gn_args'])
     elif vals['type'] == 'gyp':
       cmd = self.GYPCmd('<path>', vals['gyp_defines'], vals['gyp_config'])
     else:
@@ -309,13 +310,22 @@ class MetaBuildWrapper(object):
     return vals
 
   def RunGNGen(self, path, vals):
-    cmd = self.GNCmd(path, vals['gn_args'])
+    cmd = self.GNCmd('gen', path, vals['gn_args'])
     ret, _, _ = self.Run(cmd)
     return ret
 
-  def GNCmd(self, path, gn_args):
-    # TODO(dpranke): Find gn explicitly in the path ...
-    cmd = ['gn', 'gen', path]
+  def GNCmd(self, subcommand, path, gn_args=''):
+    if self.platform == 'linux2':
+      gn_path = os.path.join(self.chromium_src_dir, 'buildtools', 'linux64',
+                             'gn')
+    elif self.platform == 'darwin':
+      gn_path = os.path.join(self.chromium_src_dir, 'buildtools', 'mac',
+                             'gn')
+    else:
+      gn_path = os.path.join(self.chromium_src_dir, 'buildtools', 'win',
+                             'gn.exe')
+
+    cmd = [gn_path, subcommand, path]
     gn_args = gn_args.replace("$(goma_dir)", self.args.goma_dir)
     if gn_args:
       cmd.append('--args=%s' % gn_args)
@@ -408,8 +418,8 @@ class MetaBuildWrapper(object):
 
     all_needed_targets = set()
     for f in inp['files']:
-      cmd = ['gn', 'refs', self.args.path[0], '//' + f,
-             '--type=executable', '--all', '--as=output']
+      cmd = self.GNCmd('refs', self.args.path[0]) + [
+             '//' + f, '--type=executable', '--all', '--as=output']
       ret, out, _ = self.Run(cmd)
       if ret:
         self.WriteFailureAndRaise('gn refs returned %d: %s' % (ret, out),
diff --git a/tools/mb/mb_unittest.py b/tools/mb/mb_unittest.py
index 19cd87f..5613df6 100644
--- a/tools/mb/mb_unittest.py
+++ b/tools/mb/mb_unittest.py
@@ -18,6 +18,7 @@ class FakeMBW(mb.MetaBuildWrapper):
     self.calls = []
     self.out = ''
     self.err = ''
+    self.platform = 'linux2'
     self.chromium_src_dir = '/fake_src'
     self.default_config = '/fake_src/tools/mb/mb_config.pyl'
 
@@ -151,7 +152,8 @@ class UnitTest(unittest.TestCase):
                out=("python build/gyp_chromium -G 'output_dir=<path>' "
                     "-G config=Release -D goma=1 -D gomadir=/foo\n"))
     self.check(['lookup', '-c', 'gn_rel_bot', '-g', '/foo'], ret=0,
-               out=("gn gen '<path>' '--args=is_debug=false use_goma=true "
+               out=("/fake_src/buildtools/linux64/gn gen '<path>' "
+                    "'--args=is_debug=false use_goma=true "
                     "goma_dir=\"/foo\"'\n" ))
 
   def test_help(self):