Selective build clobbering feature (landmines.py and android build scripts).

build/landmines.py

Index: build/landmines.py
diff --git a/build/landmines.py b/build/landmines.py
new file mode 100644
index 0000000000000000000000000000000000000000..5254b504197c29ae67ed941e9a3eb9b6af9a3795
--- /dev/null
+++ b/build/landmines.py
@@ -0,0 +1,42 @@
+# Copyright (c) 2012 The Chromium Authors. All rights reserved.

[cmp_google, 2012/10/20 22:27:16]

before line 1, insert a #!/usr/bin/python call

+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+This file holds a list of reasons why a particular build needs to be clobbered
+(or a list of 'landmines').
+
+On every bulid, a list of landmines is generated by running this file and

[cmp_google, 2012/10/20 22:27:16]

bulid -> build

+saving its output to <build_dir>/<target>/.landmines
+
+A landmine is tripped when a builder checks out a different revision, and the
+diff between the new landmines and the old ones is non-null. At this point, the
+build is clobbered.
+"""
+
+import sys
+import json

[cmp_google, 2012/10/20 22:27:16]

line 18 before line 17

+
+# Expect no args, JSON on stdin

[cmp_google, 2012/10/20 22:27:16]

append a period

+assert len(sys.argv) == 1

[cmp_google, 2012/10/20 22:27:16]

would be better to output usage text here, and print something like lines 24-31
as an example for a user

+OPTIONS = json.load(sys.stdin)
+
+# Some keys in OPTIONS, and example values
+# target      -> release, debug
+# distributor -> goma, ib     // build distribution platform
+# platform    -> win32, mac, linux, android, ios
+# arch        -> ia32, x64, ...
+# builder     -> make, ninja, vs
+# msvs        ->
+#   version   -> 2010, 2012
+
+def o(key, default=''):

[cmp_google, 2012/10/20 22:27:16]

o is very bare, how about opt instead

+  return OPTIONS.get(key, default)
+
+MSVS_VERSION = o('msvs', {}).get('version', '')

[cmp_google, 2012/10/20 22:27:16]

this line is not used, let's remove it

+
+# Now for the good part

[cmp_google, 2012/10/20 22:27:16]

let's ditch this comment

+
+if o('distributor') == 'goma' and o('platform') == 'win32' and \
+   o('builder') == 'ninja':

[cmp_google, 2012/10/20 22:27:16]

to span multiple lines, we prefer to prepend a parens to the conditional
beginning on line 40, drop the \, and append a parens to the end of line 41

+  print 'Need to clobber winja goma due to backend cwd cache fix'

[cmp_google, 2012/10/20 22:27:16]

append a period to the end of the sentence here

let's call sys.exit(1) in this if after line 42

i'd prefer it if you encapsulated lines 40-42+ into a main() method, then called
it via something like:

if __name__ == 'main':
  sys.exit(main())