Collect failed "target"s from ninja in the compile step on Waterfall.

scripts/slave/compile.py

Index: scripts/slave/compile.py
diff --git a/scripts/slave/compile.py b/scripts/slave/compile.py
index 3a4eba45dcf4842a2c600dcdc62764ca2bb48346..0db39165e746c0caea99c0fc1745ca4822fb36dd 100755
--- a/scripts/slave/compile.py
+++ b/scripts/slave/compile.py
@@ -13,6 +13,7 @@
 
 import datetime
 import errno
+import json
 import multiprocessing
 import optparse
 import os
@@ -75,6 +76,54 @@ class EchoDict(dict):
     fh.write('\n')
 
 
+class NinjaFailedTargetCollector(object):
+  """This is to scrape the ninja output to collect failed "target"s.
+
+  A target here is actually an output node in the ninja build graph. Thus it
+  could be an object file, a lib, an executable, output of an action, etc.
+
+  When a build edge fails, its output nodes will be printed in a single line
+  in the following format these without quotes:
+      "FAILED: obj/path/to/file1.o obj/path/to/file2.o "
+      "FAILED: gen/path/to/name.cc gen/path/to/name.h "
+
+  If a target is specified in the test spec but it is not defined in the gn or
+  gyp build config, an "unknown target" error occurs in these two possible
+  formats without quotes:
+      "ninja: error: unknown target 'executable_target'"
+      "ninja: error: unknown target 'exe1', did you mean 'exe2'?"
+  """
+  NINJA_FAILURE_PREFIX = 'FAILED: '
+  NINJA_UNKNOWN_TARGET_PREFIX = 'ninja: error: unknown target '
+
+  def __init__(self, file_path):
+    self.file_path = file_path
+    self.failed_targets = []
+    self.unknown_targets = []
+    self.unrecognized_format = False
+
+  def extract(self, line):
+    if line.startswith(self.NINJA_FAILURE_PREFIX):
+      for node in line[len(self.NINJA_FAILURE_PREFIX):].split(' '):
+        node = node.strip()
+        if node:
+          self.failed_targets.append(node)
+    elif line.startswith(self.NINJA_UNKNOWN_TARGET_PREFIX):
+      parts = line[len(self.NINJA_UNKNOWN_TARGET_PREFIX):].split('\'')
+      if len(parts) >= 3 and parts[1].strip():
+        self.unknown_targets.append(parts[1].strip())
+      else:
+        self.unrecognized_format = True
+
+  def dump_as_json(self):
+    with open(self.file_path, 'wb') as f:
+      json.dump({
+          'failed_targets': self.failed_targets,
+          'unknown_targets': self.unknown_targets,
+          'unrecognized_format': self.unrecognized_format,
+      }, f)
+
+
 def ReadHKLMValue(path, value):
   """Retrieve the install path from the registry for Visual Studio 8.0 and
   Incredibuild."""
@@ -953,7 +1002,15 @@ def main_ninja(options, args):
 
     # Run the build.
     env.print_overrides()
-    exit_status = chromium_utils.RunCommand(command, env=env)
+    kwargs = {
+        'env': env,
+    }
+    failed_target_collector = None
+    if options.ninja_compile_failure:
+      failed_target_collector = NinjaFailedTargetCollector(
+          options.ninja_compile_failure)
+      kwargs['parser_func'] = failed_target_collector.extract
+    exit_status = chromium_utils.RunCommand(command, **kwargs)
     if exit_status == 0 and options.ninja_ensure_up_to_date:
       # Run the build again if we want to check that the no-op build is clean.
       filter_obj = EnsureUpToDateFilter()
@@ -967,6 +1024,8 @@ def main_ninja(options, args):
         print 'wasn\'t a no-op). Consult the first "ninja explain:" line for a'
         print 'likely culprit.'
         return 1
+    if exit_status != 0 and failed_target_collector:
+        failed_target_collector.dump_as_json()
     return exit_status
   finally:
     goma_teardown(options, env, exit_status)
@@ -1280,6 +1339,10 @@ def real_main():
                            help='Checks the output of the ninja builder to '
                                 'confirm that a second compile immediately '
                                 'the first is a no-op.')
+  option_parser.add_option('--ninja-compile-failure',
+                           help='Specify a file to dump detailed info of '
+                                'compile failure from ninja. Effective only '
+                                'when building with ninja.')
 
   options, args = option_parser.parse_args()