From fd4485a5407564cc2900e47405d0d665db499988 Mon Sep 17 00:00:00 2001
From: Bruno Oliveira <nicoddemus@gmail.com>
Date: Sat, 2 Aug 2014 18:01:28 -0300
Subject: [PATCH 1/2] Fixed assertionrewrite._read_pyc to handle corrupted pyc
 files properly

This seems to be the cause for issues #437 and #301.

--HG--
branch : assertionrewrite-currupted-pyc
---
 _pytest/assertion/rewrite.py  |  5 ++++-
 testing/test_assertrewrite.py | 22 ++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/_pytest/assertion/rewrite.py b/_pytest/assertion/rewrite.py
index 95bf4117d..589dc07d2 100644
--- a/_pytest/assertion/rewrite.py
+++ b/_pytest/assertion/rewrite.py
@@ -308,7 +308,10 @@ def _read_pyc(source, pyc):
         if (len(data) != 8 or data[:4] != imp.get_magic() or
                 struct.unpack("<l", data[4:])[0] != mtime):
             return None
-        co = marshal.load(fp)
+        try:
+            co = marshal.load(fp)
+        except (EOFError, ValueError, TypeError):  # see docs
+            return None
         if not isinstance(co, types.CodeType):
             # That's interesting....
             return None
diff --git a/testing/test_assertrewrite.py b/testing/test_assertrewrite.py
index 21e22c15f..72e2d4e10 100644
--- a/testing/test_assertrewrite.py
+++ b/testing/test_assertrewrite.py
@@ -539,3 +539,25 @@ class TestAssertionRewriteHookDetails(object):
         result.stdout.fnmatch_lines([
             '* 1 passed*',
         ])
+
+    def test_read_pyc(self, tmpdir):
+        """
+        Ensure that the `_read_pyc` can properly deal with corrupted pyc files.
+        In those circumstances it should just give up instead of generating
+        an exception that is propagated to the caller.
+        """
+        import py_compile
+        from _pytest.assertion.rewrite import _read_pyc
+
+        source = tmpdir.join('source.py')
+        pyc = source + 'c'
+
+        source.write('def test(): pass')
+        py_compile.compile(str(source), str(pyc))
+
+        contents = pyc.read(mode='rb')
+        strip_bytes = 20  # header is around 8 bytes, strip a little more
+        assert len(contents) > strip_bytes
+        pyc.write(contents[:strip_bytes], mode='wb')
+
+        assert _read_pyc(source, str(pyc)) is None  # no error

From cc092afd3b1306230449d09e34f7fceec9c1b4c1 Mon Sep 17 00:00:00 2001
From: Bruno Oliveira <nicoddemus@gmail.com>
Date: Mon, 4 Aug 2014 20:38:50 -0300
Subject: [PATCH 2/2] updated CHANGELOG and trace error message as requested in
 review

fixes issue #437

--HG--
branch : assertionrewrite-currupted-pyc
---
 CHANGELOG                    |  3 +++
 _pytest/assertion/rewrite.py | 15 ++++++++++-----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index 88ac07419..cfeb5da10 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,9 @@
 NEXT
 -----------------------------------
 
+- fix issue437 where assertion rewriting could cause pytest-xdist slaves
+  to collect different tests.
+
 - fix issue547 capsys/capfd also work when output capturing ("-s") is disabled.
 
 - address issue170: allow pytest.mark.xfail(...) to specify expected exceptions via
diff --git a/_pytest/assertion/rewrite.py b/_pytest/assertion/rewrite.py
index 589dc07d2..1f791de5e 100644
--- a/_pytest/assertion/rewrite.py
+++ b/_pytest/assertion/rewrite.py
@@ -131,7 +131,7 @@ class AssertionRewritingHook(object):
         pyc = os.path.join(cache_dir, cache_name)
         # Notice that even if we're in a read-only directory, I'm going
         # to check for a cached pyc. This may not be optimal...
-        co = _read_pyc(fn_pypath, pyc)
+        co = _read_pyc(fn_pypath, pyc, state.trace)
         if co is None:
             state.trace("rewriting %r" % (fn,))
             co = _rewrite_test(state, fn_pypath)
@@ -289,11 +289,13 @@ def _make_rewritten_pyc(state, fn, pyc, co):
         if _write_pyc(state, co, fn, proc_pyc):
             os.rename(proc_pyc, pyc)
 
-def _read_pyc(source, pyc):
+def _read_pyc(source, pyc, trace=None):
     """Possibly read a pytest pyc containing rewritten code.
 
     Return rewritten code if successful or None if not.
     """
+    if trace is None:
+        trace = lambda x: None
     try:
         fp = open(pyc, "rb")
     except IOError:
@@ -302,18 +304,21 @@ def _read_pyc(source, pyc):
         try:
             mtime = int(source.mtime())
             data = fp.read(8)
-        except EnvironmentError:
+        except EnvironmentError as e:
+            trace('_read_pyc(%s): EnvironmentError %s' % (source, e))
             return None
         # Check for invalid or out of date pyc file.
         if (len(data) != 8 or data[:4] != imp.get_magic() or
                 struct.unpack("<l", data[4:])[0] != mtime):
+            trace('_read_pyc(%s): invalid or out of date pyc' % source)
             return None
         try:
             co = marshal.load(fp)
-        except (EOFError, ValueError, TypeError):  # see docs
+        except Exception as e:
+            trace('_read_pyc(%s): marshal.load error %s' % (source, e))
             return None
         if not isinstance(co, types.CodeType):
-            # That's interesting....
+            trace('_read_pyc(%s): not a code object' % source)
             return None
         return co
     finally: