[adamcavendish]

Summary

Convert camelCase TypeScript untagged unions through one value plan shared by
models, HTTP payloads, multipart inputs, exports, and tagged payloads/type guards.
Mixed client/search tools consistently use input_schema and max_uses on the
wire, including through aliases and nested containers.

Problem

Independent type and conversion walks disagreed about inline unions, aliases,
and container depth. One convertibility flag conflated renamed types with
runtime checks: identical integer | number representations could skip strict
ambiguity checks. Raw aliases could promise ergonomic types while preserving
wire keys instead.

Public/wire representations, required symbols, and runtime effects are separate
facts. Scalar enum constraints survive all supported OpenAPI lowerers; TypeScript
does not recover them by rereading raw specifications.

Behavior

typescript-fetch.untagged_union_strategy controls camelCase union conversion:

Policy	Behavior
firstMatch (default)	Concrete matches precede fallbacks; schema order is retained; unmatched input is preserved
strict	Reject multiple original concrete matches or no match; fallbacks do not add ambiguity
raw	Expose recursive wire types and preserve union subtrees unchanged, including inline aliases

Matching checks required own fields, scalar literals/enums, array and dictionary
values, and typed extensions separately from declared fields. Nested finite
constraints intersect at their original nullability boundaries; an outer enum
does not replace an inner enum or widen its values. Untyped scalar enums match
their finite values without inheriting a synthetic string constraint from the
legacy type projection. Selection is pure:
count/select first, then invoke one original delegate. Inner strict errors
propagate without retrying another member.

Repeated nullable wrappers do not create ambiguity or promote opaque fallbacks.
Authored concrete null matches beside unrestricted fallbacks remain visible to
outer selection. Null already accepted by an inner union still reaches that
union through properties and containers. An outer wrapper can admit null without
calling a non-nullable inner converter. Enum metadata restores an extracted
nullable conversion wrapper rather than passing null to that nonnullable
delegate; already-nullable inner unions still receive null and run strict checks.
Inner finite constraints stay inside that restored wrapper, preserving outer-only
null permission consistently between properties and array items.

Productive recursion and compound conversions use static internal functions,
not a runtime schema interpreter or guards weakened to unrestricted JSON. Only
matchers reachable from union checks are emitted. Helpers are not re-exported
by public barrels. Open dictionaries retain concrete conversion alongside opaque
entries; empty/entirely opaque dictionaries remain fallbacks.

Conversion helper modules retain their own model/child-helper dependencies, so
importing a usable model does not pull unrelated models into its consumer.

Raw subtrees stay wire-typed while ordinary parents and siblings still convert.
Singleton allOf aliases preserve arrays/null and readonly dictionaries. The
same projections handle nested JSON requests, successful and lazy error
responses, JSON multipart parts, and direct tagged payloads/guards. A required
schema-nullable JSON body accepts supplied null but rejects omission. Optional
JSON bodies skip conversion only for undefined; supplied null retains the same
strict checks as direct or required conversion. Multipart preserves supplied
upload filenames, binary bytes and omitted optional parts.

Compatibility and boundaries

Generated converter names and readonly contracts are retained, including the
existing readonly-outer/plain-inner nested array contract. Preserve mode adds no
JSON converters. Helper inputs accept readonly arrays without widening public
API results. Imports, declarations, guards and expressions are laid out directly
for full Vite+ checks before and after packing; no formatter preparation or
generated-source compatibility patch is needed. CI bootstrap follows Vite+ 1.5.1
and TypeScript 7.0.2.

Published sigil-stitch 0.7.5 supplies semantic qualified utility types: models
named Record or Readonly keep their public names, while built-in references
use globalThis.Record or globalThis.Readonly. Open external declarations and
guards share their wrapper type, retaining nested imports without raw types.

The other eight generators consume retained legacy representations rather than
adopting a new enum or serialization policy. Rust library consumers exhaustively
matching IrTypeExpr must handle ScalarEnum, including its
representation_is_constraint fact distinguishing authored constraints from
legacy fallbacks and representation_nullable recording where property
nullability was extracted. Exhaustive TypeScriptFetchConfig literals initialize
untagged_union_strategy or use ..Default::default().

Matching is structural conversion dispatch, not full JSON Schema validation of
formats, bounds or every keyword. Multi-member allOf composition is not
redesigned. Same-value circular aliases remain outside this change and can still
cause TS2456; exploratory consumers do not claim full-barrel compilation when
their fixtures contain those unsupported aliases. No subprocess-driven test
harness, Python tooling/union repair, warning suppression, release change or
publication is introduced.

[codecov]

Codecov Report

❌ Patch coverage is 95.23810% with 130 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/generators/union_match.rs	93.76%	42 Missing ⚠️
src/generators/typescript/fetch/matching.rs	94.47%	19 Missing ⚠️
src/generators/typescript/fetch/tagged.rs	91.74%	18 Missing ⚠️
src/generators/typescript/fetch/layout.rs	93.57%	16 Missing ⚠️
src/generators/typescript/fetch/sigil_emit_api.rs	94.66%	15 Missing ⚠️
src/generators/typescript/fetch/plan.rs	98.18%	13 Missing ⚠️
src/generators/typescript/fetch/codegen.rs	96.77%	2 Missing ⚠️
src/ir/types/type_expr.rs	97.50%	2 Missing ⚠️
src/generators/java/okhttp/util.rs	83.33%	1 Missing ⚠️
src/generators/rust/common/emit_models.rs	80.00%	1 Missing ⚠️
... and 1 more

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