Use assert_never for enum fallbacks (#3177)

Author: adamtheturtle

pyproject.toml

@@ -385,6 +385,7 @@ run.patch = [ "subprocess" ]
 run.relative_files = true
 run.source = [ "ci/", "src/", "tests/" ]
 report.exclude_also = [
+    "case _ as unreachable:\n\\s*assert_never\\(",
     "class .*\\bProtocol\\):",
     "if TYPE_CHECKING:",
 ]

src/mock_vws/_flask_server/target_manager.py

@@ -6,6 +6,7 @@
 import json
 from enum import StrEnum, auto
 from http import HTTPMethod, HTTPStatus
+from typing import assert_never
 from zoneinfo import ZoneInfo
 
 from beartype import beartype
@@ -37,17 +38,19 @@ class _TargetRaterChoice(StrEnum):
     PERFECT = auto()
     RANDOM = auto()
 
-    def to_target_rater(self) -> TargetTrackingRater:
+    def to_target_rater(
+        self: _TargetRaterChoice,
+    ) -> TargetTrackingRater:
         """Get the target rater."""
         match self:
-            case self.BRISQUE:
+            case _TargetRaterChoice.BRISQUE:
                 return BrisqueTargetTrackingRater()
-            case self.PERFECT:
+            case _TargetRaterChoice.PERFECT:
                 return HardcodedTargetTrackingRater(rating=5)
-            case self.RANDOM:
+            case _TargetRaterChoice.RANDOM:
                 return RandomTargetTrackingRater()
-            case _:  # pragma: no cover
-                raise ValueError
+            case _ as unreachable:
+                assert_never(unreachable)
 
 
 @beartype

src/mock_vws/_flask_server/vwq.py

@@ -8,6 +8,7 @@
 import time
 from enum import StrEnum, auto
 from http import HTTPMethod, HTTPStatus
+from typing import assert_never
 
 import requests
 from beartype import beartype
@@ -39,15 +40,15 @@ class _ImageMatcherChoice(StrEnum):
     EXACT = auto()
     STRUCTURAL_SIMILARITY = auto()
 
-    def to_image_matcher(self) -> ImageMatcher:
+    def to_image_matcher(self: _ImageMatcherChoice) -> ImageMatcher:
         """Get the image matcher."""
         match self:
-            case self.EXACT:
+            case _ImageMatcherChoice.EXACT:
                 return ExactMatcher()
-            case self.STRUCTURAL_SIMILARITY:
+            case _ImageMatcherChoice.STRUCTURAL_SIMILARITY:
                 return StructuralSimilarityMatcher()
-            case _:  # pragma: no cover
-                raise ValueError
+            case _ as unreachable:
+                assert_never(unreachable)
 
 
 @beartype

src/mock_vws/_flask_server/vws.py

@@ -12,6 +12,7 @@
 import uuid
 from enum import StrEnum, auto
 from http import HTTPMethod, HTTPStatus
+from typing import assert_never
 
 import requests
 from beartype import beartype
@@ -62,15 +63,15 @@ class _ImageMatcherChoice(StrEnum):
     EXACT = auto()
     STRUCTURAL_SIMILARITY = auto()
 
-    def to_image_matcher(self) -> ImageMatcher:
+    def to_image_matcher(self: _ImageMatcherChoice) -> ImageMatcher:
         """Get the image matcher."""
         match self:
-            case self.EXACT:
+            case _ImageMatcherChoice.EXACT:
                 return ExactMatcher()
-            case self.STRUCTURAL_SIMILARITY:
+            case _ImageMatcherChoice.STRUCTURAL_SIMILARITY:
                 return StructuralSimilarityMatcher()
-            case _:  # pragma: no cover
-                raise ValueError
+            case _ as unreachable:
+                assert_never(unreachable)
 
 
 @beartype