v0.14.0: response validation fails with "schema node was not found in its root document" for multi-file specs (inline schemas with cross-file $refs)

[vibexp-gh]

Regression in v0.14.0

After upgrading from v0.13.10 to v0.14.0, ValidateHttpResponse fails at schema-compile time for any operation whose response schema is an inline schema (in an externally-referenced path file) that contains cross-file $refs — a layout used by multi-file OpenAPI projects (e.g. openapi.yaml + paths/*.yaml + schemas/*.yaml).

The error:

200 response body for '/inline-oneof' failed schema compilation: The response schema for status code '200' failed to compile: schema node was not found in its root document

It comes from buildSchemaDocumentResources → jsonPointerForNode(schemaIndex.GetRootNode(), schema.GoLow().GetRootNode()) in schema_validation/schema_resources.go: the pointer walk can't locate the schema's YAML node in the index root document.

Minimal repro

openapi.yaml:

openapi: 3.1.0
info:
  title: repro
  version: 1.0.0
paths:
  /direct-ref:
    $ref: './paths/direct.yaml#/p'
  /inline-oneof:
    $ref: './paths/inline.yaml#/p'
components:
  schemas:
    Widget:
      type: object
      properties:
        name:
          type: string

paths/direct.yaml:

p:
  get:
    responses:
      '200':
        description: ok
        content:
          application/json:
            schema:
              $ref: '../openapi.yaml#/components/schemas/Widget'

paths/inline.yaml:

p:
  get:
    responses:
      '200':
        description: ok
        content:
          application/json:
            schema:
              oneOf:
                - $ref: '../openapi.yaml#/components/schemas/Widget'
                - type: object
                  properties:
                    other:
                      type: string

Validation code:

doc, _ := libopenapi.NewDocumentWithConfiguration(raw, &datamodel.DocumentConfiguration{
    BasePath:            filepath.Dir(specPath),
    SpecFilePath:        specPath,
    AllowFileReferences: true,
})
model, _ := doc.BuildV3Model()
v := validator.NewValidatorFromV3Model(&model.Model)
ok, errs := v.ValidateHttpResponse(req, resp) // req: GET /inline-oneof, body {name:x}

Observed (v0.14.0)

case	result
/direct-ref (response schema is a bare cross-file $ref)	✅ ok
/inline-oneof (inline oneOf with cross-file $refs)	❌ schema node was not found in its root document
inline allOf with cross-file $refs (same layout)	❌ same error
inline type: array / items: {$ref: cross-file} in a path file	❌ same error
same compositions moved into components/schemas with file-internal refs	✅ ok

On v0.13.10 all of these pass.

Also possibly related: an allOf defined in an external schema file (./schemas/foo.yaml#/Bar) whose members reference another component in the root document (../openapi.yaml#/components/schemas/Baz) hits the same compile error when reached through a path-level reference.

v0.14.0, libopenapi v0.38.7, go 1.25.