Add resilience in croc to a failed build (e.g. 0 stats generated).

Makes a failure case suck less.

Review URL: http://codereview.chromium.org/660142

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@40138 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 37 insertions, 0 deletions

diff --git a/tools/code_coverage/croc.py b/tools/code_coverage/croc.py
index 9d2f3ac..1ea21ff 100755
--- a/tools/code_coverage/croc.py
+++ b/tools/code_coverage/croc.py
@@ -52,6 +52,14 @@ class CrocStatError(CrocError):
 class CoverageStats(dict):
   """Coverage statistics."""
 
+  # Default dictionary values for this stat.
+  DEFAULTS = { 'files_covered': 0,
+               'files_instrumented': 0,
+               'files_executable': 0,
+               'lines_covered': 0,
+               'lines_instrumented': 0,
+               'lines_executable': 0 }
+
   def Add(self, coverage_stats):
     """Adds a contribution from another coverage stats dict.
 
@@ -64,6 +72,15 @@ class CoverageStats(dict):
       else:
         self[k] = v
 
+  def AddDefaults(self):
+    """Add some default stats which might be assumed present.
+
+    Do not clobber if already present.  Adds resilience when evaling a
+    croc file which expects certain stats to exist."""
+    for k, v in self.DEFAULTS.iteritems():
+      if not k in self:
+        self[k] = v
+
 #------------------------------------------------------------------------------
 
 
@@ -399,6 +416,10 @@ class Coverage(object):
         return default
 
     stats = self.tree.stats_by_group[group]
+    # Unit tests use real dicts, not CoverageStats objects,
+    # so we can't AddDefaults() on them.
+    if group == 'all' and hasattr(stats, 'AddDefaults'):
+      stats.AddDefaults()
     try:
       return eval(stat, {'__builtins__': {'S': self.GetStat}}, stats)
     except Exception, e:
diff --git a/tools/code_coverage/croc_test.py b/tools/code_coverage/croc_test.py
index 035fcf9..36fc546 100644
--- a/tools/code_coverage/croc_test.py
+++ b/tools/code_coverage/croc_test.py
@@ -650,6 +650,22 @@ GetStat('nosuch') = 42
     # In the real os.walk() call this prunes the walk.
     self.assertEqual(self.mock_walk_return[0][1], ['subdir'])
 
+
+  def testEmptyTreeStats(self):
+    """Make sure we don't choke when absolutely nothing happened.
+
+    How we might hit this: bot compile error."""
+    c = self.cov_minimal
+    t = c.tree
+    t.stats_by_group['all'].AddDefaults()
+    self.assertEqual(t.stats_by_group, {
+        'all': { 'files_covered': 0,
+                 'files_instrumented': 0,
+                 'files_executable': 0,
+                 'lines_covered': 0,
+                 'lines_instrumented': 0,
+                 'lines_executable': 0 }})
+
   def testUpdateTreeStats(self):
     """Test UpdateTreeStats()."""