[gn] Automatically derive build configs in test runner.

tools/run-tests.py

Index: tools/run-tests.py
diff --git a/tools/run-tests.py b/tools/run-tests.py
index b1c71dd0a76d7e12222dbf85a2465ab4e5dd1075..7e519cfcc4762d0883ebbbbb7603105c57a4da82 100755
--- a/tools/run-tests.py
+++ b/tools/run-tests.py
@@ -30,6 +30,7 @@
 
 from collections import OrderedDict
 import itertools
+import json
 import multiprocessing
 import optparse
 import os
@@ -434,6 +435,29 @@ def ProcessOptions(options):
   global EXHAUSTIVE_VARIANTS
   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.

[vogelheim, 2016/06/30 11:08:02]

Clever. I really like this!

I still have something to [complain|improve], though: :) 

Would it make sense to - instead of checking for v8_build_config.json, to check
for presence of args.gn, and if so use the result of "gn args out/XXX --list
--short" and extract the value from there?

It seems like every single variable we use below should be in there. Also, every
future variable declared in gn would be, too. And we don't need an additional
script and build step.

[Michael Achenbach, 2016/06/30 11:47:49]

Would be nice, unfortunately, the --list command shows you only the default
values. Not what is actually set. And I didn't wanna write a parser for the
gn.args file.

[vogelheim, 2016/06/30 12:09:39]

Pity. I had indeed misunderstood what --list does. :-(

+  options.auto_detect = False
+  build_config_path = os.path.join(
+      BASE_DIR, options.outdir, "v8_build_config.json")
+  if os.path.exists(build_config_path):
+    with open(build_config_path) as f:
+      build_config = json.load(f)
+    options.auto_detect = True
+
+    options.arch_and_mode = None
+    options.arch = build_config["v8_target_cpu"]
+    if options.arch == 'x86':
+      # TODO(machenbach): Transform all to x86 eventually.
+      options.arch = 'ia32'
+    options.asan = build_config["is_asan"]
+    options.dcheck_always_on = build_config["dcheck_always_on"]
+    options.mode = 'debug' if build_config["is_debug"] else 'release'
+    options.msan = build_config["is_msan"]
+    options.no_i18n = not build_config["v8_enable_i18n_support"]
+    options.no_snap = not build_config["v8_use_snapshot"]
+    options.tsan = build_config["is_tsan"]
+
   # Architecture and mode related stuff.
   if options.arch_and_mode:
     options.arch_and_mode = [arch_and_mode.split(".")
@@ -667,6 +691,10 @@ def Execute(arch, mode, args, options, suites):
       # buildbot. Currently this is capitalized Release and Debug.
       shell_dir = os.path.join(BASE_DIR, options.outdir, mode)
       mode = BuildbotToV8Mode(mode)
+    elif options.auto_detect:
+      # If an output dir with a build was passed, test directly in that
+      # directory.
+      shell_dir = os.path.join(BASE_DIR, options.outdir)
     else:
       shell_dir = os.path.join(
           BASE_DIR,
@@ -712,6 +740,8 @@ def Execute(arch, mode, args, options, suites):
                         sancov_dir=options.sancov_dir)
 
   # TODO(all): Combine "simulator" and "simulator_run".
+  # TODO(machenbach): In GN we can derive simulator run from
+  # target_arch != v8_target_arch in the dumped build config.
   simulator_run = not options.dont_skip_simulator_slow_tests and \
       arch in ['arm64', 'arm', 'mipsel', 'mips', 'mips64', 'mips64el', \
                'ppc', 'ppc64'] and \