fix(typescript): add undefined to index signature for optional properties - #3472
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…ties An interface with both properties and typed additionalProperties emitted an index signature that omitted `undefined`, so optional properties of type `T | undefined` failed `tsc --strict` with TS2411. Also dedupe the index signature members and drop the union when additionalProperties is `any`. Fixes #3123 Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
schani
enabled auto-merge (squash)
September 6, 2026 02:19
Generated-output differences162 files differ — 125 modified, 37 new, 0 deleted |
PHP emits no class for a top-level object with additionalProperties, so the driver echoes the input and the negative sample cannot fail. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Generated-output differences161 files differ — 125 modified, 36 new, 0 deleted |
class-with-additional.schema already covers an optional property next to typed additionalProperties, and class-map-union.schema covers the dedupe and any cases. With strictNullChecks on they catch TS2411. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Generated-output differences125 files differ — 125 modified, 0 new, 0 deleted |
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Fixes #3123
Why
An interface with both
propertiesand a typedadditionalPropertiesgets an index signature. TypeScript requires every declared property to be assignable to it. Optional properties have typeT | undefined, and the index signature omittedundefined, sotsc --strictfailed with TS2411:The fixtures never caught this because
test/fixtures/typescript/tsconfig.jsondisabledstrictNullChecks.What
undefined(voidfor Flow) to the index signature when any property is optional.class-map-union.schemapreviously emittedboolean | BarObject | boolean | number | BarObject | boolean | BarObject | string.any/unknownwhenadditionalPropertiesisany, instead ofunknown | number.strictNullChecksin the TypeScript fixture. With it on, the existingclass-with-additional.schemareproduces the TS2411 error before the fix, andclass-map-union.schemacovers the dedupe andanycases.Supersedes #3127.
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