Fix typing issues of StringSetFlag (#107)

* Selectively ignore override errors as this is a custom class
* Use a separate interface declaration file (.pyi) by refactoring out
  StringSetFlag class from the utils module to overcome limitation of
  mypy semantic analysis on "__ror__ = __or__" in subclasses of
  Enum/Flag classes.

changes/107.fix.md

@@ -0,0 +1 @@
+Fix typing issues of `StringSetFlag` by refactoring it using a separate interface definition file

src/ai/backend/common/enum_extension.py

@@ -0,0 +1,57 @@
+from __future__ import annotations
+
+import enum
+
+__all__ = (
+    'StringSetFlag',
+)
+
+
+class StringSetFlag(enum.Flag):
+
+    def __eq__(self, other):
+        return self.value == other
+
+    def __hash__(self):
+        return hash(self.value)
+
+    def __or__(self, other):
+        if isinstance(other, type(self)):
+            other = other.value
+        if not isinstance(other, (set, frozenset)):
+            other = set((other,))
+        return set((self.value,)) | other
+
+    __ror__ = __or__
+
+    def __and__(self, other):
+        if isinstance(other, (set, frozenset)):
+            return self.value in other
+        if isinstance(other, str):
+            return self.value == other
+        raise TypeError
+
+    __rand__ = __and__
+
+    def __xor__(self, other):
+        if isinstance(other, (set, frozenset)):
+            return set((self.value,)) ^ other
+        if isinstance(other, str):
+            if other == self.value:
+                return set()
+            else:
+                return other
+        raise TypeError
+
+    def __rxor__(self, other):
+        if isinstance(other, (set, frozenset)):
+            return other ^ set((self.value,))
+        if isinstance(other, str):
+            if other == self.value:
+                return set()
+            else:
+                return other
+        raise TypeError
+
+    def __str__(self):
+        return self.value

src/ai/backend/common/enum_extension.pyi

@@ -0,0 +1,22 @@
+import enum
+
+
+class StringSetFlag(enum.Flag):
+    def __eq__(self, other: object) -> bool: ...
+    def __hash__(self) -> int: ...
+    def __or__(  # type: ignore[override]
+        self,
+        other: StringSetFlag | str | set[str] | frozenset[str],
+    ) -> set[str]: ...
+    def __and__(  # type: ignore[override]
+        self,
+        other: StringSetFlag | str | set[str] | frozenset[str],
+    ) -> bool: ...
+    def __xor__(  # type: ignore[override]
+        self,
+        other: StringSetFlag | str | set[str] | frozenset[str],
+    ) -> set[str]: ...
+    def __ror__(self, other: StringSetFlag | str | set[str] | frozenset[str]) -> set[str]: ...
+    def __rand__(self, other: StringSetFlag | str | set[str] | frozenset[str]) -> bool: ...
+    def __rxor__(self, other: StringSetFlag | str | set[str] | frozenset[str]) -> set[str]: ...
+    def __str__(self) -> str: ...

src/ai/backend/common/utils.py

@@ -3,7 +3,6 @@
 import base64
 from collections import OrderedDict
 from datetime import timedelta
-import enum
 from itertools import chain
 import numbers
 import random
@@ -34,6 +33,7 @@
     current_loop,
     run_through,
 )
+from .enum_extension import StringSetFlag  # for legacy imports  # noqa
 from .files import AsyncFileWriter  # for legacy imports  # noqa
 from .networking import (  # for legacy imports  # noqa
     curl,
@@ -198,56 +198,6 @@ def str_to_timedelta(tstr: str) -> timedelta:
     return timedelta(**params)  # type: ignore
 
 
-class StringSetFlag(enum.Flag):
-
-    def __eq__(self, other):
-        return self.value == other
-
-    def __hash__(self):
-        return hash(self.value)
-
-    def __or__(self, other):
-        if isinstance(other, type(self)):
-            other = other.value
-        if not isinstance(other, (set, frozenset)):
-            other = set((other,))
-        return set((self.value,)) | other
-
-    __ror__ = __or__
-
-    def __and__(self, other):
-        if isinstance(other, (set, frozenset)):
-            return self.value in other
-        if isinstance(other, str):
-            return self.value == other
-        raise TypeError
-
-    __rand__ = __and__
-
-    def __xor__(self, other):
-        if isinstance(other, (set, frozenset)):
-            return set((self.value,)) ^ other
-        if isinstance(other, str):
-            if other == self.value:
-                return set()
-            else:
-                return other
-        raise TypeError
-
-    def __rxor__(self, other):
-        if isinstance(other, (set, frozenset)):
-            return other ^ set((self.value,))
-        if isinstance(other, str):
-            if other == self.value:
-                return set()
-            else:
-                return other
-        raise TypeError
-
-    def __str__(self):
-        return self.value
-
-
 class FstabEntry:
     """
     Entry class represents a non-comment line on the `fstab` file.

tests/test_utils.py

@@ -12,14 +12,14 @@
 import pytest
 
 from ai.backend.common.asyncio import AsyncBarrier, run_through
+from ai.backend.common.enum_extension import StringSetFlag
 from ai.backend.common.files import AsyncFileWriter
 from ai.backend.common.networking import curl
 from ai.backend.common.utils import (
     odict, dict2kvlist, nmget,
     generate_uuid, get_random_seq,
     readable_size_to_bytes,
     str_to_timedelta,
-    StringSetFlag,
 )
 from ai.backend.common.testutils import (
     mock_corofunc, mock_awaitable, AsyncContextManagerMock,
@@ -156,9 +156,7 @@ async def test_curl_returns_default_value_if_not_success(mocker) -> None:
 
 def test_string_set_flag() -> None:
 
-    # FIXME: Remove "type: ignore" when mypy gets released with
-    #        python/mypy#11579.
-    class MyFlags(StringSetFlag):   # type: ignore
+    class MyFlags(StringSetFlag):
         A = 'a'
         B = 'b'
 
@@ -182,7 +180,7 @@ class MyFlags(StringSetFlag):   # type: ignore
     assert {'b'} == MyFlags.A ^ {'a', 'b'}
     assert {'a', 'b', 'c'} == MyFlags.A ^ {'b', 'c'}
     with pytest.raises(TypeError):
-        123 & MyFlags.A
+        123 & MyFlags.A  # type: ignore[operator]
 
     assert {'a', 'c'} & MyFlags.A
     assert not {'a', 'c'} & MyFlags.B