[rust] fix: make enumUnknownDefaultCase catch unknown enum values

TE
3d ago
+88-0

Fixes #25291
Related: #25271 also changes rust/model.mustache (oneOf with an enum discriminator), in a different section.

With enumUnknownDefaultCase=true the rust client adds an UnknownDefaultOpenApi variant to each enum without #[serde(other)]. So only the literal "unknown_default_open_api" / 11184809 maps to it, and any other value outside the spec still fails to deserialize.

Changes:

  • rust/model.mustache: add #[serde(other)] to the injected unknown variant (the last enumVars entry, only when enumUnknownDefaultCase is set). This covers schema-level and inline property enums, for both string enums (Deserialize) and integer enums (Deserialize_repr; serde_repr supports #[serde(other)]).
  • Serialization does not change: the variant still serializes as "unknown_default_open_api" / 11184809.
  • Output without the option does not change.

Not covered: the rust-server and rust-axum generators. They use separate templates.

Testing:

  • New RustClientCodegenTest#testEnumUnknownDefaultCaseUsesSerdeOther with src/test/resources/3_0/rust/enum-unknown-default-case.yaml. The test fails without the template change.
  • I generated a crate from that spec with the option on and ran a cargo test against it: unknown string, schema-level and integer values deserialize to UnknownDefaultOpenApi, and known values are unchanged.
  • No existing rust sample uses enumUnknownDefaultCase, so regenerating the samples changed nothing.

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cc @frol @farcaller @richardwhiuk @paladinzh @jacob-pro @dsteeley

Summary by cubic

Makes enumUnknownDefaultCase work as documented in the Rust client: unknown enum values now deserialize to the UnknownDefaultOpenApi variant instead of erroring.

Previously the variant only matched its serialized literal ("unknown_default_open_api" / 11184809), so any other out-of-spec value failed deserialization. The injected variant now carries #[serde(other)], which applies to schema-level and inline enums for both string and integer types. Serialization behavior and output without the option are unchanged.

  • Affects the rust generator only; rust-server and rust-axum use separate templates.