Quote keys containing '=' when writing (fixes #273)

src/configobj/__init__.py

@@ -1760,7 +1760,7 @@ def _unquote(self, value):
         return value
 
 
-    def _quote(self, value, multiline=True):
+    def _quote(self, value, multiline=True, is_key=False):
         """
         Return a safely quoted version of a value.
 
@@ -1808,7 +1808,12 @@ def _quote(self, value, multiline=True):
         check_for_single = (no_lists_no_quotes or not need_triple) and not hash_triple_quote
 
         if check_for_single:
-            if not self.list_values:
+            if is_key and '=' in value:
+                # A key containing '=' must be quoted, otherwise the first
+                # '=' is read back as the key/value divider, splitting the
+                # key and corrupting the value on the next parse.
+                quot = self._get_single_quote(value)
+            elif not self.list_values:
                 # we don't quote if ``list_values=False``
                 quot = noquot
             # for normal values either single or double quotes will do
@@ -1992,7 +1997,7 @@ def _write_line(self, indent_string, entry, this_entry, comment):
         else:
             val = repr(this_entry)
         return '%s%s%s%s%s' % (indent_string,
-                               self._decode_element(self._quote(entry, multiline=False)),
+                               self._decode_element(self._quote(entry, multiline=False, is_key=True)),
                                self._a_to_u(' = '),
                                val,
                                self._decode_element(comment))

src/tests/test_configobj.py

@@ -1295,6 +1295,19 @@ def test_hash_escaping(self, empty_cfg):
         empty_cfg.write(collector)
         assert collector.getvalue() == b'a = "b # something", "c # something"\n'
 
+    def test_key_with_equals_is_quoted(self, empty_cfg):
+        # issue #273: a key containing '=' was written unquoted, so on the
+        # next parse the first '=' was read as the key/value divider,
+        # splitting the key and corrupting the value.
+        empty_cfg.newlines = '\n'
+        empty_cfg['a = b'] = 'val'
+        collector = io.BytesIO()
+        empty_cfg.write(collector)
+        assert collector.getvalue() == b'"a = b" = val\n'
+        # and the written form round-trips back to the original key/value
+        collector.seek(0)
+        assert dict(ConfigObj(collector)) == {'a = b': 'val'}
+
     def test_detecting_line_endings_from_existing_files(self):
         for expected_line_ending in ('\r\n', '\n'):
             with open('temp', 'w') as h: