Add an option --gn to run-tests.py that just runs the latest gn build

tools/run-tests.py

 #!/usr/bin/env python
 #
 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 16 matching lines @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 
 from collections import OrderedDict
 import itertools
 import json
 import multiprocessing
 import optparse
 import os
-from os.path import join
+from os.path import getmtime, isdir, join
 import platform
 import random
 import shlex
 import subprocess
 import sys
 import time
 
 from testrunner.local import execution
 from testrunner.local import progress
 from testrunner.local import testsuite
 from testrunner.local.variants import ALL_VARIANTS
 from testrunner.local import utils
 from testrunner.local import verbose
 from testrunner.network import network_execution
 from testrunner.objects import context
 
 
 # Base dir of the v8 checkout to be used as cwd.
 BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 
+DEFAULT_OUT_GN = "out.gn"
+
 ARCH_GUESS = utils.DefaultArch()
 
 # Map of test name synonyms to lists of test suites. Should be ordered by
 # expected runtimes (suites with slow test cases first). These groups are
 # invoked in seperate steps on the bots.
 TEST_MAP = {
   # This needs to stay in sync with test/bot_default.isolate.
   "bot_default": [
     "mjsunit",
     "cctest",
@@ skipping 219 matching lines @@
                     default=False, dest="no_variants", action="store_true")
   result.add_option("--variants",
                     help="Comma-separated list of testing variants;"
                     " default: \"%s\"" % ",".join(VARIANTS))
   result.add_option("--exhaustive-variants",
                     default=False, action="store_true",
                     help="Use exhaustive set of default variants:"
                     " \"%s\"" % ",".join(EXHAUSTIVE_VARIANTS))
   result.add_option("--outdir", help="Base directory with compile output",
                     default="out")
+  result.add_option("--gn", help="Scan out.gn for the last built configuration",
+                    default=False, action="store_true")
   result.add_option("--predictable",
                     help="Compare output of several reruns of each test",
                     default=False, action="store_true")
   result.add_option("-p", "--progress",
                     help=("The style of progress indicator"
                           " (verbose, dots, color, mono)"),
                     choices=progress.PROGRESS_INDICATORS.keys(), default="mono")
   result.add_option("--quickcheck", default=False, action="store_true",
                     help=("Quick check mode (skip slow tests)"))
   result.add_option("--report", help="Print a summary of the tests to be run",
@@ skipping 113 matching lines @@
       'history_size=7',
       'report_destroy_locked=0',
     ])
 
 def ProcessOptions(options):
   global VARIANTS
 
   # First try to auto-detect configurations based on the build if GN was
   # used. This can't be overridden by cmd-line arguments.
   options.auto_detect = False
+  if options.gn:
+    gn_out_dir = os.path.join(BASE_DIR, DEFAULT_OUT_GN)
+    latest_timestamp =  -1

[Michael Achenbach, 2016/08/30 11:32:17]

nit: space too much

[jochen (gone - plz use gerrit), 2016/08/30 11:40:59]

done

+    latest_config = None
+    for gn_config in os.listdir(gn_out_dir):
+      gn_config_dir = os.path.join(gn_out_dir, gn_config)
+      if not isdir(gn_config_dir):
+        continue
+      if os.path.getmtime(gn_config_dir) > latest_timestamp:

[Michael Achenbach, 2016/08/30 11:32:17]

The modified time of the directory only changes if you add/remove files. What if
all files keep existing and are just modified?

[jochen (gone - plz use gerrit), 2016/08/30 11:40:59]

I think compiling will always first remove the target and add it (at least in my
local test that seems to work)

+        latest_timestamp = os.path.getmtime(gn_config_dir)
+        latest_config = gn_config
+    if latest_config:
+      options.outdir = os.path.join(DEFAULT_OUT_GN, latest_config)
+
   build_config_path = os.path.join(
       BASE_DIR, options.outdir, "v8_build_config.json")
   if os.path.exists(build_config_path):
     try:
       with open(build_config_path) as f:
         build_config = json.load(f)
     except Exception:
       print ("%s exists but contains invalid json. Is your build up-to-date?" %
              build_config_path)
       return False
@@ skipping 439 matching lines @@
         "--coverage-dir=%s" % options.sancov_dir])
     except:
       print >> sys.stderr, "Error: Merging sancov files failed."
       exit_code = 1
 
   return exit_code
 
 
 if __name__ == "__main__":
   sys.exit(Main())