Upgrade to coverage 3.7.1 and have it auto-build itself on first use.

scripts/slave/unittests/test_env.py

Index: scripts/slave/unittests/test_env.py
diff --git a/scripts/slave/unittests/test_env.py b/scripts/slave/unittests/test_env.py
index f299b6f780c55ff28d36a3a6fe0f07718975122c..832b4bc79942c66d5fbe6d45320eeeb6c95bbb60 100644
--- a/scripts/slave/unittests/test_env.py
+++ b/scripts/slave/unittests/test_env.py
@@ -22,22 +22,46 @@ sys.path.insert(0, os.path.join(BASE_DIR, 'third_party', 'buildbot_slave_8_4'))
 sys.path.insert(0, os.path.join(BASE_DIR, 'third_party', 'twisted_10_2'))
 sys.path.insert(0, os.path.join(BASE_DIR, 'third_party', 'mock-1.0.1'))
 
-try:
-  # The C-compiled coverage engine is WAY faster than the pure python version.
-  # If we have it, then don't bother with the pure python one.
-  import coverage
-except ImportError:
-  sys.path.insert(0, os.path.join(BASE_DIR, 'third_party', 'coverage-3.6'))
-  import coverage
-
-def print_coverage_warning():
-  if not hasattr(coverage.collector, 'CTracer'):
-    print "WARNING: Using the pure-python coverage module."
-    print "         Install the native python coverage module to speed recipe"
-    print "         training up by an order of magnitude."
-    print
-    print "           pip install coverage"
-    print "         OR"
-    print "           easy_install coverage"
+def ensure_coverage_importable():
+  try:
+    from distutils.version import StrictVersion
+    import coverage
+    if (StrictVersion(coverage.__version__) < StrictVersion('3.7') or
+        not coverage.collector.CTracer):
+      del sys.modules['coverage']
+      del coverage
+    else:
+      return
+  except ImportError:
+    pass
+
+  from pkg_resources import get_build_platform
+  try:
+    # Python 2.7 or >= 3.2
+    from sysconfig import get_python_version
+  except ImportError:
+    from distutils.sysconfig import get_python_version
+
+  cov_dir = os.path.join(BASE_DIR, 'third_party', 'coverage-3.7.1')
+  cov_egg = os.path.join(cov_dir, 'dist', 'coverage-3.7.1-py%s-%s.egg' % (

[Vadim Sh., 2014/04/04 19:21:59]

That's what bdist_egg produces? It there a way to FORCE it to produce this file,
instead of guessing it?

[iannucci, 2014/04/04 19:34:35]

This is taken from setuptools' code. I can force get_build_platform, but not
get_python_version. Setuptools is going to import these exact same functions
anyway.

+      get_python_version(), get_build_platform()))
+
+  # The C-compiled coverage engine is WAY faster (and less buggy) than the pure
+  # python version, so we build the dist_egg if necessary.
+  if not os.path.exists(cov_egg):
+    import subprocess
+    print 'Building Coverage 3.7.1'
+    p = subprocess.Popen([sys.executable, 'setup.py', 'bdist_egg'], cwd=cov_dir,

[Vadim Sh., 2014/04/04 19:21:59]

It may be worth to add some instructions how to build it on windows. OR, allow
system-wide coverage 3.7.1 to be used on windows and refer to
https://pypi.python.org/packages/2.7/c/coverage/coverage-3.7.1.win32-py2.7.ex...
(or whatever, from PyPI: https://pypi.python.org/pypi/coverage/3.7.1)

That may be easier than requiring working MSVC environment.

[Vadim Sh., 2014/04/04 19:32:21]

Oh, it's already possible to import it from system location. Then just add a
pointer to PyPI page? To let people know that failure on windows is
half-expected and there's a workaround.

[iannucci, 2014/04/04 19:34:35]

Yeah I wasn't sure how to support windows, but if you look at the first import
block at the top, if there is a correctly-configured system-wide python, it'll
take that.

I'll add a message on windows which links to 'how to install python-coverage on
winders'

[Vadim Sh., 2014/04/04 19:47:08]

Also, bdist_egg needs python-dev and setuptools, right? They are not installed
by default...

+                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    stdout, stderr = p.communicate()
+    if p.returncode != 0:
+      print 'Error while building :('
+      print stdout
+      print stderr
+      sys.exit(1)
+
+  sys.path.insert(0, cov_egg)

[Vadim Sh., 2014/04/04 19:21:59]

Call 'ensure_coverage_importable' again, to ensure it is importable now? With a
flag to disable auto build...

[iannucci, 2014/04/04 19:34:35]

? It's called below... it will either pass (and coverage will be importable) or
it will sys.exit.

[Vadim Sh., 2014/04/04 19:47:08]

I mean second time, after egg is build, to assert it is indeed used. Well, fine.

+
+ensure_coverage_importable()
 
 from common import find_depot_tools  # pylint: disable=W0611