Ignore the "c_string_encoding" directive when looking for a "coding" cookie in...

Ignore the "c_string_encoding" directive when looking for a "coding" cookie in the first two source lines.
Closes #2632.

CHANGES.rst

@@ -148,6 +148,10 @@ Bugs fixed
   the return value was non-null.
   Original patch by Matt Wozniski (Github Issue #2603)
 
+* The source file encoding detection could get confused if the
+  ``c_string_encoding`` directive appeared within the first two lines.
+  (Github issue #2632)
+
 Other changes
 -------------
 

Cython/Utils.py

@@ -238,7 +238,7 @@ def decode_filename(filename):
 
 # support for source file encoding detection
 
-_match_file_encoding = re.compile(b"coding[:=]\s*([-\w.]+)").search
+_match_file_encoding = re.compile(br"(\w*coding)[:=]\s*([-\w.]+)").search
 
 
 def detect_opened_file_encoding(f):
@@ -254,8 +254,8 @@ def detect_opened_file_encoding(f):
         if not data:
             break
     m = _match_file_encoding(lines[0])
-    if m:
-        return m.group(1).decode('iso8859-1')
+    if m and m.group(1) != b'c_string_encoding':
+        return m.group(2).decode('iso8859-1')
     elif len(lines) > 1:
         m = _match_file_encoding(lines[1])
         if m:

tests/run/str_default_auto_encoding.pyx

-# cython: c_string_type = str
-# cython: c_string_encoding = default
+# cython: c_string_encoding=default
+# cython: c_string_type=str
+
+# NOTE: the directive order above is specifically meant to trigger (and confuse) the
+# source encoding detector with "coding=default".
 
 import sys
 if sys.version_info[0] >= 3: