Recover from corrupted fixed-format cache meta file (#20780)

JukkaL · web-flow · commit 825c0bb1edae · 2026-02-11T15:26:53.000Z
Various read functions may raise AssertionError in addition to
ValueError.
diff --git a/mypy/cache.py b/mypy/cache.py
@@ -224,7 +224,7 @@ def read(cls, data: ReadBuffer, data_file: str) -> CacheMeta | None:
                 ignore_all=read_bool(data),
                 plugin_data=read_json_value(data),
             )
-        except ValueError:
+        except (ValueError, AssertionError):
             return None
 
 

Original file line number	Diff line number	Diff line change
`@@ -224,7 +224,7 @@ def read(cls, data: ReadBuffer, data_file: str) -> CacheMeta \| None:`
`224`	`224`	`ignore_all=read_bool(data),`
`225`	`225`	`plugin_data=read_json_value(data),`
`226`	`226`	`)`
`227`		`- except ValueError:`
	`227`	`+ except (ValueError, AssertionError):`
`228`	`228`	`return None`
`229`	`229`
`230`	`230`