A fix for coding declarations, bug #529

3 files changed, 67 insertions, 1 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 431fa19b..637537ec 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -40,6 +40,9 @@ Unreleased
     call stack printed for every line in the multi-line config output. This is
     now fixed.
 
+- Fixed an unusual bug involving multiple coding declarations affecting code
+  containing code in multi-line strings: `issue 529`_.
+  
 - Corrected the name of the jquery.ba-throttle-debounce.js library. Thanks,
   Ben Finney.  Closes `issue 505`_.
 
@@ -51,6 +54,7 @@ Unreleased
 .. _issue 511: https://bitbucket.org/ned/coveragepy/issues/511/version-42-coverage-combine-empties
 .. _issue 516: https://bitbucket.org/ned/coveragepy/issues/516/running-coverage-combine-twice-deletes-all
 .. _issue 525: https://bitbucket.org/ned/coveragepy/issues/525/coverage-combine-when-not-in-parallel-mode
+.. _issue 529: https://bitbucket.org/ned/coveragepy/issues/529/encoding-marker-may-only-appear-on-the
 
 
 Version 4.2 --- 2016-07-26
diff --git a/coverage/phystokens.py b/coverage/phystokens.py
index 5e80ed54..9a697b60 100644
--- a/coverage/phystokens.py
+++ b/coverage/phystokens.py
@@ -290,5 +290,9 @@ def compile_unicode(source, filename, mode):
 @contract(source='unicode', returns='unicode')
 def neuter_encoding_declaration(source):
     """Return `source`, with any encoding declaration neutered."""
-    source = COOKIE_RE.sub("# (deleted declaration)", source, count=2)
+    if COOKIE_RE.search(source):
+        source_lines = source.splitlines(True)
+        for lineno in range(min(2, len(source_lines))):
+            source_lines[lineno] = COOKIE_RE.sub("# (deleted declaration)", source_lines[lineno])
+        source = "".join(source_lines)
     return source
diff --git a/tests/test_phystokens.py b/tests/test_phystokens.py
index ccbe01b0..68456b5b 100644
--- a/tests/test_phystokens.py
+++ b/tests/test_phystokens.py
@@ -5,6 +5,7 @@
 
 import os.path
 import re
+import textwrap
 
 from coverage import env
 from coverage.phystokens import source_token_lines, source_encoding
@@ -177,6 +178,63 @@ class NeuterEncodingDeclarationTest(CoverageTest):
                 "Wrong encoding in %r" % neutered
             )
 
+    def test_two_encoding_declarations(self):
+        input_src = textwrap.dedent(u"""\
+            # -*- coding: ascii -*-
+            # -*- coding: utf-8 -*-
+            # -*- coding: utf-16 -*-
+            """)
+        expected_src = textwrap.dedent(u"""\
+            # (deleted declaration) -*-
+            # (deleted declaration) -*-
+            # -*- coding: utf-16 -*-
+            """)
+        output_src = neuter_encoding_declaration(input_src)
+        self.assertEqual(expected_src, output_src)
+
+    def test_one_encoding_declaration(self):
+        input_src = textwrap.dedent(u"""\
+            # -*- coding: utf-16 -*-
+            # Just a comment.
+            # -*- coding: ascii -*-
+            """)
+        expected_src = textwrap.dedent(u"""\
+            # (deleted declaration) -*-
+            # Just a comment.
+            # -*- coding: ascii -*-
+            """)
+        output_src = neuter_encoding_declaration(input_src)
+        self.assertEqual(expected_src, output_src)
+
+
+class Bug529Test(CoverageTest):
+    """Test of bug 529"""
+
+    def test_bug_529(self):
+        self.make_file("the_test.py", '''\
+            # -*- coding: utf-8 -*-
+            import unittest
+            class FailsUnderCoverageTest(unittest.TestCase):
+                def test_fails_under_coverage(self):
+                    src1 = u"""\\
+                        # -*- coding: utf-8 -*-
+                        # Just a comment.
+                        """
+                    src2 = u"""\\
+                        # -*- coding: utf-8 -*-
+                        # Just a comment.
+                        """
+                    self.assertEqual(src1, src2)
+
+            if __name__ == "__main__":
+                unittest.main()
+            ''')
+        status, out = self.run_command_status("coverage run the_test.py")
+        self.assertEqual(status, 0)
+        self.assertIn("OK", out)
+        # If this test fails, the output will be super-confusing, because it
+        # has a failing unit test contained within the failing unit test.
+
 
 class CompileUnicodeTest(CoverageTest):
     """Tests of compiling Unicode strings."""