fix coding cookie detection logic

CHANGELOG

@@ -1,3 +1,8 @@
+Changes between 2.4.2 and 2.4.3
+-----------------------------------
+
+- In assertion rewriting mode on Python 2, fix the detection of coding cookies.
+
 Changes between 2.4.1 and 2.4.2
 -----------------------------------
 

_pytest/assertion/rewrite.py

@@ -196,7 +196,7 @@ def _write_pyc(state, co, source_path, pyc):
 RN = "\r\n".encode("utf-8")
 N = "\n".encode("utf-8")
 
-cookie_re = re.compile("coding[:=]\s*[-\w.]+")
+cookie_re = re.compile(r"^[ \t\f]*#.*coding[:=][ \t]*[-\w.]+")
 BOM_UTF8 = '\xef\xbb\xbf'
 
 def _rewrite_test(state, fn):
@@ -220,8 +220,8 @@ def _rewrite_test(state, fn):
         end1 = source.find("\n")
         end2 = source.find("\n", end1 + 1)
         if (not source.startswith(BOM_UTF8) and
-            (not cookie_re.match(source[0:end1]) or
+            cookie_re.match(source[0:end1]) is None and
-            not cookie_re.match(source[end1:end2]))):
+            cookie_re.match(source[end1:end2]) is None):
             if hasattr(state, "_indecode"):
                 return None  # encodings imported us again, we don't rewrite
             state._indecode = True

testing/test_assertrewrite.py

@@ -441,7 +441,6 @@ class TestAssertionRewriteHookDetails(object):
             '* 3 passed*',
         ])
 
-
     @pytest.mark.skipif("sys.version_info[0] >= 3")
     def test_assume_ascii(self, testdir):
         content = "u'\xe2\x99\xa5'"
@@ -450,6 +449,13 @@ class TestAssertionRewriteHookDetails(object):
         assert res.ret != 0
         assert "SyntaxError: Non-ASCII character" in res.stdout.str()
 
+    @pytest.mark.skipif("sys.version_info[0] >= 3")
+    def test_detect_coding_cookie(self, testdir):
+        testdir.tmpdir.join("test_utf8.py").write("""# -*- coding: utf-8 -*-
+u"St\xc3\xa4d"
+def test_rewritten():
+    assert "@py_builtins" in globals()""", "wb")
+        assert testdir.runpytest().ret == 0
 
     def test_write_pyc(self, testdir, tmpdir, monkeypatch):
         from _pytest.assertion.rewrite import _write_pyc