bpo-42345: Literal equality no longer depends on order of arguments

python · miss-islington · Nov 17, 2020 · Nov 15, 2020 · Nov 15, 2020 · Nov 15, 2020
commit 03637e2cb248f7ebf7ac45f6ecce439ffe3f6c61
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
@@ -559,6 +559,15 @@ def test_no_multiple_subscripts(self):
         with self.assertRaises(TypeError):
             Literal[1][1]
 
+    def test_equal(self):
+        self.assertEqual(Literal[1, 2], Literal[2, 1])
+        self.assertNotEqual(Literal[1, True], Literal[1])
+
+    def test_flatten(self):
+        self.assertEqual(Literal[Literal[1], Literal[2], Literal[3]], Literal[1, 2, 3])
+        self.assertEqual(Literal[Literal[1, 2], 3], Literal[1, 2, 3])
+        self.assertEqual(Literal[Literal[1, 2, 3]], Literal[1, 2, 3])
+
 
 XK = TypeVar('XK', str, bytes)
 XV = TypeVar('XV')

diff --git a/Lib/typing.py b/Lib/typing.py
@@ -228,6 +228,17 @@ def _remove_dups_flatten(parameters):
     return tuple(params)
 
 
+def _flatten_literal_params(parameters):
+    """An internal helper for Literal creation: flatten Literals among parameters"""
+    params = []
+    for p in parameters:
+        if isinstance(p, _LiteralGenericAlias):
+            params.extend(p.__args__)
+        else:
+            params.append(p)
+    return tuple(params)
+
+
 _cleanups = []
 
 
@@ -460,7 +471,11 @@ def open_helper(file: str, mode: MODE) -> str:
     """
     # There is no '_type_check' call because arguments to Literal[...] are
     # values, not types.
-    return _GenericAlias(self, parameters)
+    if not isinstance(parameters, tuple):
+        parameters = (parameters,)
+
+    parameters = _flatten_literal_params(parameters)
+    return _LiteralGenericAlias(self, parameters)
 
 
 @_SpecialForm
@@ -930,6 +945,14 @@ def __subclasscheck__(self, cls):
                 return True
 
 
+class _LiteralGenericAlias(_GenericAlias, _root=True):
+
+    def __eq__(self, other):
+        if not isinstance(other, _LiteralGenericAlias):
+            return NotImplemented
+
+        return len(self.__args__) == len(other.__args__) and set(self.__args__) == set(other.__args__)
+
 
 class Generic:
     """Abstract base class for generic types.

diff --git a/Misc/ACKS b/Misc/ACKS
@@ -861,6 +861,7 @@ Jan Kanis
 Rafe Kaplan
 Jacob Kaplan-Moss
 Allison Kaptur
+Yurii Karabas
 Janne Karila
 Per Øyvind Karlsen
 Anton Kasyanov

diff --git a/Misc/NEWS.d/next/Library/2020-11-15-15-23-34.bpo-42345.hiIR7x.rst b/Misc/NEWS.d/next/Library/2020-11-15-15-23-34.bpo-42345.hiIR7x.rst
@@ -0,0 +1,2 @@
+Literal equality no longer depends on order of arguments. Patch provided by
+Yurii Karabas.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Literal equality no longer depends on order of arguments. Patch provided by
		Yurii Karabas.