Fix creating CIMultiDict from MultiDict not making keys case-insentive

multidict/_multidict.c

@@ -78,7 +78,7 @@ _multidict_extend(MultiDictObject *self, PyObject *arg,
     }
 
     if (arg != NULL) {
-        if (MultiDict_CheckExact(arg) || CIMultiDict_CheckExact(arg)) {
+        if (CIMultiDict_CheckExact(arg) || (!CIMultiDict_CheckExact(self) && MultiDict_CheckExact(arg))) {
             list = &((MultiDictObject*)arg)->pairs;
             if (pair_list_update_from_pair_list(&self->pairs, used, list) < 0) {
                 goto fail;

multidict/_multidict_py.py

@@ -453,6 +453,8 @@ def _title(self, key: str) -> str:
 
 
 class _CIMixin:
+    _ci: bool = True
+
     def _key(self, key: str) -> str:
         if type(key) is istr:
             return key
@@ -474,6 +476,7 @@ def _title(self, key: str) -> str:
 
 class _Base(MultiMapping[_V]):
     _impl: _Impl[_V]
+    _ci: bool = False
 
     @abstractmethod
     def _key(self, key: str) -> str: ...
@@ -628,7 +631,10 @@ def _extend(
     ) -> None:
         if arg:
             if isinstance(arg, (MultiDict, MultiDictProxy)):
-                items = arg._impl._items
+                if self._ci and not arg._ci:
+                    items = [(self._title(k), k, v) for _, k, v in arg._impl._items]
+                else:
+                    items = arg._impl._items
                 if kwargs:
                     for key, value in kwargs.items():
                         items.append((self._title(key), key, value))

tests/test_multidict.py

@@ -19,6 +19,8 @@
     MultiMapping,
     MutableMultiMapping,
 )
+from multidict._multidict_py import CIMultiDict as PyCIMultiDict
+from multidict._multidict_py import MultiDict as PyMultiDict
 
 _T = TypeVar("_T")
 
@@ -1189,3 +1191,38 @@ def test_items_case_insensitive_isdisjoint(
     ) -> None:
         d = cls([("KEY", "one")])
         assert d.items().isdisjoint(arg) == expected
+
+
+def test_convert_multidict_to_cimultidict() -> None:
+    """Test conversion from MultiDict to CIMultiDict."""
+    start_as_md = MultiDict([("KEY", "value1"), ("key2", "value2")])
+    assert start_as_md.get("KEY") == "value1"
+    assert start_as_md["KEY"] == "value1"
+    assert start_as_md.get("key2") == "value2"
+    assert start_as_md["key2"] == "value2"
+    start_as_cimd = CIMultiDict([("KEY", "value1"), ("key2", "value2")])
+    assert start_as_cimd.get("key") == "value1"
+    assert start_as_cimd["key"] == "value1"
+    assert start_as_cimd.get("key2") == "value2"
+    assert start_as_cimd["key2"] == "value2"
+    converted_to_ci = CIMultiDict(start_as_md)
+    assert converted_to_ci.get("key") == "value1"
+    assert converted_to_ci["key"] == "value1"
+    assert converted_to_ci.get("key2") == "value2"
+    assert converted_to_ci["key2"] == "value2"
+
+
+def test_pure_python_convert_multidict_to_cimultidict_eq() -> None:
+    """Test compare after conversion from MultiDict to CIMultiDict."""
+    original = PyMultiDict([("h1", "header1"), ("h2", "header2"), ("h3", "header3")])
+    assert PyCIMultiDict(original) == PyCIMultiDict(
+        [("H1", "header1"), ("H2", "header2"), ("H3", "header3")]
+    )
+
+
+def test_convert_multidict_to_cimultidict_eq() -> None:
+    """Test compare after conversion from MultiDict to CIMultiDict."""
+    original = MultiDict([("h1", "header1"), ("h2", "header2"), ("h3", "header3")])
+    assert CIMultiDict(original) == CIMultiDict(
+        [("H1", "header1"), ("H2", "header2"), ("H3", "header3")]
+    )