fix(graphql): keep distinct GraphQL types with identical shape separate

[schani]

Bug

Distinct GraphQL object types with identical structure were collapsed into a single output class. For example:

type GridConfig {
  items: [ComponentRef]
}

type GridProps {
  items: [ComponentRef]
}

type Grid {
  config: GridConfig
  props: GridProps
}

produced a single merged GridConfigClass used for both config and props, instead of two separate GridConfig/GridProps interfaces. --no-combine-classes had no effect, since that flag only applies to JSON input.

Root cause

quicktype's class type identity/deduplication (classTypeIdentity in TypeBuilder.getClassType) and the CombineClasses graph-rewrite pass both compared classes purely by structural shape (their properties). For JSON/JSON Schema input this is desired — structurally-identical inferred classes should unify. But GraphQL input already knows which types are distinct (from the schema itself), and separate GraphQL types should never be unified just because they happen to have the same fields.

Fix

• packages/quicktype-graphql-input/src/index.ts: each class built from a GraphQL object type is now tagged with a new identity TypeAttributeKind (graphqlTypeName) carrying the GraphQL schema type's name.
• packages/quicktype-core/src/Type/Type.ts: added haveSameIdentityAttributes(a, b) helper. Class type identity in TypeBuilder.getClassType already includes identity attributes, so classes with different GraphQL type names are never unified there.
• packages/quicktype-core/src/rewrites/CombineClasses.ts: the CombineClasses rewrite pass now also requires haveSameIdentityAttributes before considering two class prototypes combinable, so structurally-identical-but-distinct GraphQL classes are not merged there either. Repeated uses of the same GraphQL type still dedupe as before, since they carry the same identity attribute.

This only affects GraphQL input; JSON/JSON Schema-derived classes carry no such identity attribute, so their existing structural deduplication/combining behavior is unchanged.

Test coverage

• New GraphQL fixture: test/inputs/graphql/separate-types1.graphql + separate-types.gqlschema + separate-types1.1.json, modeled on the issue's Grid/GridConfig/GridProps example, wired into the existing graphql fixture mechanism (test/fixtures.ts).
• New unit test test/unit/graphql-separate-types.test.ts: renders TypeScript from that GraphQL input with combineClasses both true and false, and asserts the output keeps Config and Props as two separate interfaces, while a genuinely-repeated type (Item) still dedupes to one interface.

Verification

• npm run build — passes.
• npm run test:unit — 172/172 tests pass.
• QUICKTEST=true FIXTURE=graphql-typescript script/test — 10/10 tests pass (including the new separate-types1.graphql fixture).
• Manually re-ran the issue's exact repro command against the built CLI: GridConfig/GridProps are now emitted as separate interfaces (both with and without --no-combine-classes), while the shared ComponentRef type used by both remains a single interface.
• Full GraphQL fixture suite (all languages) was not run locally since several target-language toolchains aren't installed in this environment; CI will validate those.

Fixes #1072

🤖 Generated with Claude Code

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8423 changed lines — +7830 / −593

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[github-actions]

Generated-output differences

111 files differ — 43 modified, 62 new, 6 deleted
8423 changed lines — +7830 / −593

Open the generated-output report →