René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"A oneOf/anyOf branch that is a whole-file `$ref` generates Go that doesn't parse","articleBody":"When a `oneOf` or `anyOf` branch is a `$ref` to a whole file (`$ref: ./user.yaml`, no `#` fragment), the union's `As*`/`From*`/`Merge*` accessors are named after the branch's inline Go type, so the generated code has methods like `AsStruct {\\n Name *string ... }()` and formatting fails.\n\nWhole-file refs are otherwise generated inline (`IsGoTypeReference` returns false for them, #308): the same file used directly as a body schema or as a property works, and an inline branch (`- {type: object, properties: ...}`) in the same union gets its own type, `GetItems200JSONResponseBody0`.\n\n## Reproduction\n\n`openapi.yaml`:\n\n```yaml\nopenapi: 3.0.3\ninfo: {title: t, version: \"1\"}\npaths:\n  /items:\n    get:\n      responses:\n        \"200\":\n          description: ok\n          content:\n            application/json:\n              schema:\n                oneOf:\n                  - $ref: ./user.yaml\n                  - $ref: ./group.yaml\n```\n\n`user.yaml`:\n\n```yaml\ntype: object\nproperties:\n  name: {type: string}\n```\n\n`group.yaml`:\n\n```yaml\ntype: object\nproperties:\n  id: {type: integer}\n```\n\n```console\n$ oapi-codegen -generate types -package api -o api.gen.go openapi.yaml\nerror generating code: error formatting Go code at line 53: api.go:53:5: expected declaration, found Name (and 2 more errors)\n```\n\nNo configuration file. The unformatted output (with `output-options: skip-fmt: true`) shows where it breaks:\n\n```go\n        // AsStruct {\n    Name *string`json:\"name,omitempty\"`\n} returns the union data inside the GetItems200JSONResponseBody as a struct {\n    Name *string`json:\"name,omitempty\"`\n}\n        func (t GetItems200JSONResponseBody) AsStruct {\n    Name *string`json:\"name,omitempty\"`\n}() (struct {\n```\n\nThe same happens with `anyOf`, with only one branch being a whole-file ref, with `openapi: 3.1.0`, for a property's `oneOf`, and for a component schema (`components.schemas.Item: {oneOf: [$ref: ./user.yaml, $ref: ./group.yaml]}`, referenced from the response). The component form fails the same way on v2.4.1 through v2.6.0; the inline body form has failed since v2.7.0, when inline body unions started getting accessors.\n\n## Expected\n\nThe branches are generated like inline ones: `GetItems200JSONResponseBody0` and `GetItems200JSONResponseBody1`, with `AsGetItems200JSONResponseBody0()` and so on, and the code compiles. Or, if whole-file refs aren't meant to be supported as union branches, an error that says so.\n\n## Versions\n\nv2.8.1 and `main` (15f5714, `v2.8.1-0.20261028140811-15f571472ff8`, error at line 56 there), Go 1.27.3, linux/amd64.\n\n## Likely cause\n\n`generateUnionElement` (`pkg/codegen/union.go:88` on main) names and defines a branch only when `element.Ref == \"\"`. A whole-file ref has a non-empty `Ref`, but `generateGoSchema` inlined it, so its `GoType` is the struct literal. Checking `!IsGoTypeReference(element.Ref)` there instead makes both forms above generate the `...0`/`...1` types, and the output compiles; I haven't run the test suite on that change.\n","author":{"url":"https://github.com/BogdanYarotsky","@type":"Person","name":"BogdanYarotsky"},"datePublished":"2026-10-29T06:28:20Z","url":"https://github.com/oapi-codegen/oapi-codegen/issues/2639"}