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SiyetSiyet
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Narrow none_member in JSON schema union handling (#1121)
Follow-up to #1028. #1028 introduced `none_member: mi.Type | None` in the union branch of `_json_schema.py` and guarded the `self.to_schema(none_member)` calls with a separate `has_none` boolean. mypy can't narrow `none_member` through the flag, so it errors: ``` _json_schema.py:363: error: Argument 1 to "to_schema" of "_SchemaGenerator" has incompatible type "Type | None"; expected "Type" [arg-type] ``` This is not caught by current CI because the msgspec source is not type-checked there (only `tests/typing` is); #1116 (adding stubtest) is what surfaces it. Fixing it here so #1116 can go green. The fix drops the redundant `has_none` flag and checks `none_member is not None` at the call sites, which gives mypy the narrowing. No runtime behavior change (`has_none` and `none_member` were always set together): `tests/unit/test_schema.py` still passes (115), and stubtest with mypy 2.2.0 is clean. Co-authored-by: Siyet <[email protected]>
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Lines changed: 4 additions & 6 deletions

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‎src/msgspec/_json_schema.py‎

Lines changed: 4 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -330,7 +330,6 @@ def to_schema(self, t: mi.Type, check_ref: bool = True) -> dict[str, Any]:
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elif isinstance(t, mi.UnionType):
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structs = {}
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other = []
333-
has_none = False
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none_member = None
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tag_field = None
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for subtype in t.types:
@@ -341,7 +340,6 @@ def to_schema(self, t: mi.Type, check_ref: bool = True) -> dict[str, Any]:
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tag_field = real_type.tag_field
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structs[real_type.tag] = real_type
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elif isinstance(real_type, mi.NoneType):
344-
has_none = True
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none_member = subtype
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else:
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other.append(subtype)
@@ -359,21 +357,21 @@ def to_schema(self, t: mi.Type, check_ref: bool = True) -> dict[str, Any]:
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}
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if options:
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options.append(struct_schema)
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if has_none:
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if none_member is not None:
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options.append(self.to_schema(none_member))
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schema["anyOf"] = options
365-
elif has_none:
363+
elif none_member is not None:
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schema["anyOf"] = [struct_schema, self.to_schema(none_member)]
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else:
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schema.update(struct_schema)
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elif len(structs) == 1:
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_, subtype = structs.popitem()
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options.append(self.to_schema(subtype))
372-
if has_none:
370+
if none_member is not None:
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options.append(self.to_schema(none_member))
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schema["anyOf"] = options
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else:
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if has_none:
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if none_member is not None:
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options.append(self.to_schema(none_member))
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schema["anyOf"] = options
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elif isinstance(t, mi.LiteralType):

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