Preserve comments on merge.

dev-requirements.txt

@@ -2,8 +2,8 @@
 # Development requirements
 #
 
-invoke==0.12.2
-#rituals==0.3.0
+# invoke==0.12.2
+# rituals==0.3.0
 -e git+https://github.com/jhermann/rituals.git#egg=rituals
 
 Sphinx==1.3.4

src/configobj/__init__.py

@@ -760,6 +760,14 @@ def merge(self, indict, decoupled=False):
         >>> c2
         ConfigObj({'section1': {'option1': 'False', 'subsection': {'more_options': 'False'}}})
         """
+        if hasattr(indict, "initial_comment") and indict.initial_comment:
+            self.initial_comment = indict.initial_comment
+        if hasattr(indict, "final_comment") and indict.final_comment:
+            self.final_comment = indict.final_comment
+        if hasattr(indict, "comments") and indict.comments:
+            for k, comment_lines in indict.comments.items():
+                if comment_lines:
+                    self.comments[k] = comment_lines
         for key, val in indict.items():
             if decoupled:
                 val = copy.deepcopy(val)

src/tests/test_configobj.py

@@ -1299,6 +1299,36 @@ def test_merge_coupling(self, data):
         c1['sect']['val'] = 42
         assert c2['sect']['val'] == data[1]
 
+    @pytest.mark.parametrize(
+        "lines1,lines2,expected_lines",
+        [
+            (
+                # both c1 and c2 have comments
+                ["# c1 before config", "[main]", "# c1 for foo", "foo = a", "# c1 after config"],
+                ["# c2 before config", "[main]", "# c2 for foo", "foo = b", "# c2 after config"],
+                ["# c2 before config", "[main]", "# c2 for foo", "foo = b", "# c2 after config"],
+            ),
+            (
+                # c1 has comments, c2 does not
+                ["# c1 before config", "[main]", "# c1 for foo", "foo = a", "# c1 after config"],
+                ["[main]", "foo = b"],
+                ["# c1 before config", "[main]", "# c1 for foo", "foo = b", "# c1 after config"],
+            ),
+            (
+                # c2 has comments, c1 does not
+                ["[main]", "foo = a"],
+                ["# c2 before config", "[main]", "# c2 for foo", "foo = b", "# c2 after config"],
+                ["# c2 before config", "[main]", "# c2 for foo", "foo = b", "# c2 after config"],
+            ),
+        ]
+    )
+    def test_merge_comments(self, lines1, lines2, expected_lines):
+        c1 = ConfigObj(lines1)
+        c2 = ConfigObj(lines2)
+        c1.merge(c2)
+        # comments and values from c2 should win
+        actual_lines = c1.write()
+        assert actual_lines == expected_lines
 
 class TestErrorReporting(object):
     MULTI_ERROR = [