Properly deal with .pyc files missing their sources.

2 files changed, 81 insertions, 10 deletions

diff --git a/coverage/control.py b/coverage/control.py
index 1044fad0..16a92971 100644
--- a/coverage/control.py
+++ b/coverage/control.py
@@ -307,19 +307,35 @@ class Coverage(object):
         return os.path.split(morf_filename)[0]
 
     def _source_for_file(self, filename):
-        """Return the source file for `filename`."""
+        """Return the source file for `filename`.
+
+        Given a filename being traced, return the best guess as to the source
+        file to attribute it to.
+
+        """
         if filename.endswith(".py"):
+            # .py files are themselves source files.
             return filename
+
         elif filename.endswith((".pyc", ".pyo")):
-            try_filename = filename[:-1]
-            if os.path.exists(try_filename):
-                return try_filename
+            # Bytecode files probably have source files near them.
+            py_filename = filename[:-1]
+            if os.path.exists(py_filename):
+                # Found a .py file, use that.
+                return py_filename
             if sys.platform == "win32":
-                try_filename += "w"
-                if os.path.exists(try_filename):
-                    return try_filename
-        elif filename.endswith("$py.class"):    # Jython
-            filename = filename[:-9] + ".py"
+                # On Windows, it could be a .pyw file.
+                pyw_filename = py_filename + "w"
+                if os.path.exists(pyw_filename):
+                    return pyw_filename
+            # Didn't find source, but it's probably the .py file we want.
+            return py_filename
+
+        elif filename.endswith("$py.class"):
+            # Jython is easy to guess.
+            return filename[:-9] + ".py"
+
+        # No idea, just use the filename as-is.
         return filename
 
     def _name_for_module(self, module_globals, filename):
diff --git a/tests/test_summary.py b/tests/test_summary.py
index fa5b4461..77381186 100644
--- a/tests/test_summary.py
+++ b/tests/test_summary.py
@@ -1,6 +1,12 @@
 """Test text-based summary reporting for coverage.py"""
 
-import os, re, sys
+import glob
+import os
+import py_compile
+import re
+import sys
+
+from nose.plugins.skip import SkipTest
 
 import coverage
 from coverage.backward import StringIO
@@ -438,6 +444,55 @@ class SummaryTest(CoverageTest):
             self.assertIn("start.pyw 2 0 100%", report)
             self.assertIn("mod.pyw 1 0 100%", report)
 
+    def test_tracing_pyc_file(self):
+        # Create two Python files.
+        self.make_file("mod.py", "a = 1\n")
+        self.make_file("main.py", "import mod\n")
+
+        # Make one into a .pyc.
+        py_compile.compile("mod.py")
+
+        # Run the program.
+        cov = coverage.coverage()
+        cov.start()
+        import main     # pragma: nested # pylint: disable=import-error,unused-variable
+        cov.stop()      # pragma: nested
+
+        report = self.get_report(cov).splitlines()
+        self.assertIn("mod.py 1 0 100%", report)
+
+    def test_missing_py_file_during_run(self):
+        # PyPy2 doesn't run bare .pyc files.
+        if '__pypy__' in sys.builtin_module_names and sys.version_info < (3,):
+            raise SkipTest("PyPy2 doesn't run bare .pyc files")
+
+        # Create two Python files.
+        self.make_file("mod.py", "a = 1\n")
+        self.make_file("main.py", "import mod\n")
+
+        # Make one into a .pyc, and remove the .py.
+        py_compile.compile("mod.py")
+        os.remove("mod.py")
+
+        # Python 3 puts the .pyc files in a __pycache__ directory, and will
+        # not import from there without source.  It will import a .pyc from
+        # the source location though.
+        if not os.path.exists("mod.pyc"):
+            pycs = glob.glob("__pycache__/mod.*.pyc")
+            self.assertEqual(len(pycs), 1)
+            os.rename(pycs[0], "mod.pyc")
+
+        # Run the program.
+        cov = coverage.coverage()
+        cov.start()
+        import main     # pragma: nested # pylint: disable=import-error,unused-variable
+        cov.stop()      # pragma: nested
+
+        # Put back the missing Python file.
+        self.make_file("mod.py", "a = 1\n")
+        report = self.get_report(cov).splitlines()
+        self.assertIn("mod.py 1 0 100%", report)
+
 
 class SummaryTest2(CoverageTest):
     """Another bunch of summary tests."""