Add a "buildbucket" subcommand to mb.

This subcommand prints the trybot configuration in the
buildbucket.config format expected by gerrit. This should hopefully
make it a little easier to maintain the buildbucket.config file.

Bug: 
Change-Id: I7d956efb6c08128ae0ceaa6b68bcc9001296549c
Reviewed-on: https://chromium-review.googlesource.com/568666Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Peter Collingbourne <pcc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491647}

tools/mb/docs/user_guide.md

@@ -167,6 +167,18 @@ The `-f/--config-file` and `-q/--quiet` flags work as documented for
 This is mostly useful as a presubmit check and for verifying changes to
 the config file.
 
+### `mb gerrit-buildbucket-config`
+
+Generates a gerrit buildbucket configuration file and prints it to
+stdout. This file contains the list of trybots shown in gerrit's UI.
+
+The master copy of the buildbucket.config file lives
+in a separate branch of the chromium repository. Run `mb
+gerrit-buildbucket-config > buildbucket.config.new && git fetch origin
+refs/meta/config:refs/remotes/origin/meta/config && git checkout
+-t -b meta_config origin/meta/config && mv buildbucket.config.new
+buildbucket.config` to update the file.
+
 ## Isolates and Swarming
 
 `mb gen` is also responsible for generating the `.isolate` and

tools/mb/mb.py

@@ -56,6 +56,7 @@ class MetaBuildWrapper(object):
     self.sep = os.sep
     self.args = argparse.Namespace()
     self.configs = {}
+    self.luci_tryservers = {}
     self.masters = {}
     self.mixins = {}
 
@@ -235,6 +236,14 @@ class MetaBuildWrapper(object):
                            ' do compiles')
     subp.set_defaults(func=self.CmdAudit)
 
+    subp = subps.add_parser('gerrit-buildbucket-config',
+                            help='Print buildbucket.config for gerrit '
+                            '(see MB user guide)')
+    subp.add_argument('-f', '--config-file', metavar='PATH',
+                      default=self.default_config,
+                      help='path to config file (default is %(default)s)')
+    subp.set_defaults(func=self.CmdBuildbucket)
+
     subp = subps.add_parser('help',
                             help='Get help on a subcommand.')
     subp.add_argument(nargs='?', action='store', dest='subcommand',
@@ -368,6 +377,25 @@ class MetaBuildWrapper(object):
 
     return ret
 
+  def CmdBuildbucket(self):
+    self.ReadConfigFile()
+
+    self.Print('# This file was generated using '
+               '"tools/mb/mb.py gerrit-buildbucket-config".')
+
+    for luci_tryserver in sorted(self.luci_tryservers):
+      self.Print('[bucket "luci.%s"]' % luci_tryserver)
+      for bot in sorted(self.luci_tryservers[luci_tryserver]):
+        self.Print('\tbuilder = %s' % bot)
+
+    for master in sorted(self.masters):
+      if master.startswith('tryserver.'):
+        self.Print('[bucket "master.%s"]' % master)
+        for bot in sorted(self.masters[master]):
+          self.Print('\tbuilder = %s' % bot)
+
+    return 0
+
   def CmdValidate(self, print_ok=True):
     errs = []
 
@@ -674,6 +702,7 @@ class MetaBuildWrapper(object):
                  (self.args.config_file, e))
 
     self.configs = contents['configs']
+    self.luci_tryservers = contents['luci_tryservers']
     self.masters = contents['masters']
     self.mixins = contents['mixins']
 

tools/mb/mb_config.pyl

@@ -520,6 +520,7 @@
       'cast_shell_audio_linux': 'cast_audio_release_trybot',
       'chromeos_amd64-generic_chromium_compile_only_ng': 'cros_chrome_sdk',
       'chromeos_daisy_chromium_compile_only_ng': 'cros_chrome_sdk',
+      'chromium_presubmit': 'presubmit',
       'closure_compilation': 'closure_compilation',
       'fuchsia': 'release_trybot_fuchsia',
       'fuchsia_compile': 'release_trybot_fuchsia',
@@ -1409,6 +1410,11 @@
       'ozone_linux', 'release_trybot',
     ],
 
+    'presubmit': [
+      # The chromium_presubmit bot does not use mb.
+      'error',
+    ],
+
     'release_afl_asan': [
       'release', 'afl', 'asan', 'chromeos_codecs', 'pdf_xfa', 'disable_nacl',
     ],
@@ -1981,4 +1987,8 @@
       'gn_args': 'target_cpu="x86"',
     },
   },
+
+  'luci_tryservers': {
+    'chromium.try': [ 'LUCI linux_chromium_rel_ng' ],
+  },
 }

tools/mb/mb_unittest.py

@@ -122,6 +122,7 @@ TEST_CONFIG = """\
       'fake_args_file_twice': 'args_file_twice',
     },
   },
+  'luci_tryservers': {},
   'configs': {
     'args_file_goma': ['args_file', 'goma'],
     'args_file_twice': ['args_file', 'args_file'],
@@ -181,6 +182,7 @@ TEST_BAD_CONFIG = """\
       'b': 'gn_rel_bot_2',
     },
   },
+  'luci_tryservers': {},
   'mixins': {
     'gn': {'type': 'gn'},
     'chrome_with_codecs': {
@@ -205,6 +207,7 @@ GYP_HACKS_CONFIG = """\
       'fake_builder': 'fake_config',
     },
   },
+  'luci_tryservers': {},
   'configs': {
     'fake_config': ['fake_mixin'],
   },
@@ -220,6 +223,28 @@ GYP_HACKS_CONFIG = """\
 }
 """
 
+TRYSERVER_CONFIG = """\
+{
+  'masters': {
+    'not_a_tryserver': {
+      'fake_builder': 'fake_config',
+    },
+    'tryserver.chromium.linux': {
+      'try_builder': 'fake_config',
+    },
+    'tryserver.chromium.mac': {
+      'try_builder2': 'fake_config',
+    },
+  },
+  'luci_tryservers': {
+    'luci_tryserver1': ['luci_builder1'],
+    'luci_tryserver2': ['luci_builder2'],
+  },
+  'configs': {},
+  'mixins': {},
+}
+"""
+
 
 class UnitTest(unittest.TestCase):
   def fake_mbw(self, files=None, win32=False):
@@ -555,6 +580,22 @@ class UnitTest(unittest.TestCase):
                     "LLVM_FORCE_HEAD_REVISION=1\n"
                     "python build/gyp_chromium -G output_dir=_path_\n"))
 
+  def test_buildbucket(self):
+    mbw = self.fake_mbw()
+    mbw.files[mbw.default_config] = TRYSERVER_CONFIG
+    self.check(['gerrit-buildbucket-config'], mbw=mbw,
+               ret=0,
+               out=('# This file was generated using '
+                    '"tools/mb/mb.py gerrit-buildbucket-config".\n'
+                    '[bucket "luci.luci_tryserver1"]\n'
+                    '\tbuilder = luci_builder1\n'
+                    '[bucket "luci.luci_tryserver2"]\n'
+                    '\tbuilder = luci_builder2\n'
+                    '[bucket "master.tryserver.chromium.linux"]\n'
+                    '\tbuilder = try_builder\n'
+                    '[bucket "master.tryserver.chromium.mac"]\n'
+                    '\tbuilder = try_builder2\n'))
+
 
 if __name__ == '__main__':
   unittest.main()