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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"v2.8.0 regression: infinite recursion / stack overflow on self-referential allOf+anyOf schemas (side effect of #1904/#1905)","articleBody":"## Description\n\n`oapi-codegen` v2.8.0 introduced an infinite recursion / stack overflow regression when generating types for a self-referential schema where the recursive `$ref` sits inside an `allOf`, and the referenced schema itself has a top-level `anyOf`/`oneOf`.\n\nThis appears to be a side effect of the fix for #1905 (PR #1904). That fix makes `mergeOpenapiSchemas` propagate a merged schema's `oneOf`/`anyOf` members up to the caller instead of silently dropping them (which is correct — dropping them was a real bug). However, unlike the sibling `allOf` merge path, which tracks visited `$ref`s via `seenSchemaRef` to guard against cycles, the new `oneOf`/`anyOf` propagation added by #1904 has **no cycle detection at all**. When the propagated `anyOf`/`oneOf` transitively re-enters the same `allOf` merge, generation recurses forever instead of terminating or erroring.\n\n## Minimal reproduction\n\n`spec.yaml`:\n```yaml\nopenapi: 3.0.0\ninfo:\n  title: repro\n  version: \"1.0.0\"\npaths: {}\ncomponents:\n  schemas:\n    Node:\n      anyOf:\n        - type: object\n          properties:\n            leaf:\n              type: string\n        - type: object\n          properties:\n            children:\n              type: array\n              items:\n                allOf:\n                  - $ref: '#/components/schemas/Node'\n                  - type: object\n                    properties:\n                      extra:\n                        type: string\n```\n\n`cfg.yaml`:\n```yaml\npackage: repro\ngenerate:\n  models: true\noutput: out.gen.go\n```\n\n```\ngo run github.com/oapi-codegen/oapi-codegen/v2/cmd/oapi-codegen -config cfg.yaml spec.yaml\n```\n\n### Result on v2.8.0\n\nImmediate stack overflow:\n\n```\nruntime: goroutine stack exceeds 1000000000-byte limit\nfatal error: stack overflow\n\ngoroutine 1 [running]:\ngithub.com/oapi-codegen/oapi-codegen/v2/pkg/codegen.mergeSchemas(...)\n\tpkg/codegen/merge_schemas.go:24\ngithub.com/oapi-codegen/oapi-codegen/v2/pkg/codegen.MergeSchemas(...)\n\tpkg/codegen/merge_schemas.go:21\ngithub.com/oapi-codegen/oapi-codegen/v2/pkg/codegen.GenerateGoSchema(...)\n\tpkg/codegen/schema.go:852\ngithub.com/oapi-codegen/oapi-codegen/v2/pkg/codegen.oapiSchemaToGoType(...)\n\tpkg/codegen/schema.go:1233\ngithub.com/oapi-codegen/oapi-codegen/v2/pkg/codegen.GenerateGoSchema(...)\n\tpkg/codegen/schema.go:1210\ngithub.com/oapi-codegen/oapi-codegen/v2/pkg/codegen.GenerateGoSchema(...)\n\tpkg/codegen/schema.go:1005\ngithub.com/oapi-codegen/oapi-codegen/v2/pkg/codegen.generateUnion(...)\n\tpkg/codegen/schema.go:1629\ngithub.com/oapi-codegen/oapi-codegen/v2/pkg/codegen.GenerateGoSchema(...)\n\tpkg/codegen/schema.go:1051\ngithub.com/oapi-codegen/oapi-codegen/v2/pkg/codegen.mergeSchemas(...)\n\tpkg/codegen/merge_schemas.go:112\ngithub.com/oapi-codegen/oapi-codegen/v2/pkg/codegen.MergeSchemas(...)\n\tpkg/codegen/merge_schemas.go:21\n... (repeats identically until the goroutine stack limit is hit)\n```\n\n### Result on v2.7.2 (before #1904)\n\nGeneration succeeds, but silently drops the recursive `$ref` from the `allOf` — the exact data-loss bug #1905/#1904 set out to fix:\n\n```go\n// Node1 defines model for .\ntype Node1 struct {\n\tChildren *[]struct {\n\t\tExtra *string `json:\"extra,omitempty\"`\n\t} `json:\"children,omitempty\"`\n}\n```\n\nNote `Node1.Children` items have no reference back to `Node` at all — the recursive member of the `allOf` was dropped entirely.\n\n## Where we hit this\n\nWe hit this generating a Go client from Kibana's OpenAPI spec, on a real recursive schema shaped exactly like the repro (`Kibana_HTTP_APIs_ContentPackIncludedObjects`, a content-pack \"included objects\" tree with a `routing` array whose items are `allOf: [$ref: self, {destination}]`). Upgrading `oapi-codegen` from v2.7.2 to v2.8.0 turned a silent correctness bug (dropped recursive ref) into a hard crash.\n\n## Suggested fix\n\nExtend the same `seenSchemaRef` cycle-guard already used for `allOf` members in `mergeAllOf`/`mergeSchemas` to the `oneOf`/`anyOf` propagation added in `mergeOpenapiSchemas` (PR #1904), so a schema that re-enters an `allOf` merge it's already inside of is skipped/short-circuited instead of re-expanded indefinitely.\n\n## Environment\n\n- `oapi-codegen` v2.8.0 (regression vs v2.7.2)\n- Go 1.26.1, darwin/arm64 (also reproduces regardless of platform — this is pure recursion, not a goroutine-stack-size issue)\n","author":{"url":"https://github.com/tobio","@type":"Person","name":"tobio"},"datePublished":"2026-08-26T07:53:08Z","url":"https://github.com/oapi-codegen/oapi-codegen/issues/2542"}