In split/multi-file projects - Option for referencing via the root document

No implementation files or tests are named. Start by locating the split/multi-file reference generation and CLI option entry points, then compare them with the attached current and proposed examples. Done should include an option that consistently emits root-file section references, including the unresolved nested subsection case, with coverage for the documented examples.

Enhancement request for split/multi-file process. Only reference the root YAML file and then reference by section of the root file.

For example, a split schema file currently references another schema file by $ref: "schemas/SchemaName.yaml". My request is to allow a CLI flag/option to change these references to look like $ref: "../../root.yaml#components/schemas/SchemaName" where the reference looks at the root YAML file and specifies the section from that file.

Reason for request:
One use case I encountered is maintaining multiple versions (e.g. 0.1.0 and 0.2.0) of a schema with the same name. Differentiating between the two in the API is outside the scope of this issue. The best way to maintain concurrent versions is to utilize OpenAPI's oneOf to reference multiple possible schemas.

Example code snippet:

components:
    schemas:
        TheSchema:
            oneOf:
                - $ref: "components/schemas/TheSchema_0.1.0.yaml"
                - $ref: "components/schemas/TheSchema_0.2.0.yaml"

This versioning occurs AFTER utilizing openapi-format to split an OpenAPI file. However, there are two reasons this change is convenient:

• It keeps the file references simple
  • only one file reference all the time, only need to track the relative depth
  • section references within the root YAML look the same as the original YAML file (plus the prepended root YAML file path, of course)
• Adding multiple version references requires only two things:
  • the root YAML be updated using oneOf (see example above)
  • the addition of the schema files
  • all references to the multiple schema versions propagate downstream to any schemas/paths/etc which reference it, without any other changes

Current behavior:
The root OpenAPI file references other sections via path to the split files. However, whenever something is referenced (e.g a schema referencing another schema, a path referencing a schema, etc.) outside of the root file, it references the file directly rather than the root YAML and corresponding section/item. Below is a brief snippet example of a root YAML, schema, and path for that schema:

# root.yaml
openapi: 3.0.3
info:
  title: splitting example
  version: 0.0.1
paths:
  /some-schemas:
    $ref: "paths/someschemas.yaml"
components:
  schemas:
    SomeSchema:
      $ref: "components/schemas/SomeSchema.yaml"

# components/schemas/SomeSchema.yaml
# The file AnotherSchema.yaml was not included here to keep the examples short.
description: "SomeSchema description"
required:
  - someSchemaProperty
properties:
  someSchemaProperty:
    description: "someSchemaProperty description"
    type: string
    nullable: false
  anotherSchema:
    allOf:
      - $ref: "schemas/AnotherSchema.yaml"
      - nullable: false
      - description: "AnotherSchema used in SomeSchema"

# paths/someschemas.yaml
post:
  tags:
    - SomeSchema
  summary: "SomeSchema path summary"
  description: "SomeSchema path description"
  operationId: post-some-schema
  parameters: []
  requestBody:
    description: "SomeSchema path request body"
    content:
      application/json:
        schema:
          $ref: "../components/schemas/SomeSchema.yaml"
  responses:
    "200":
      description: "SomeSchema path response"
      content:
      application/json:
        schema:
          $ref: "../components/schemas/SomeSchema.yaml"

Proposed behavior:
Keep the root YAML the same. Within other split files, refer back to the root YAML file and then refer to the section instead. Example of the change mirrors the above examples, but with $ref path changes:

# root.yaml
openapi: 3.0.3
info:
  title: splitting example
  version: 0.0.1
paths:
  /some-schemas:
    $ref: "paths/someschemas.yaml"
components:
  schemas:
    SomeSchema:
      $ref: "components/schemas/SomeSchema.yaml"

# components/schemas/SomeSchema.yaml
# The file AnotherSchema.yaml was not included here to keep the examples short.
description: "SomeSchema description"
required:
  - someSchemaProperty
properties:
  someSchemaProperty:
    description: "someSchemaProperty description"
    type: string
    nullable: false
  anotherSchema:
    allOf:
      - $ref: "../../root.yaml#components/schemas/AnotherSchema"
      - nullable: false
      - description: "AnotherSchema used in SomeSchema"

# paths/someschemas.yaml
post:
  tags:
    - SomeSchema
  summary: "SomeSchema path summary"
  description: "SomeSchema path description"
  operationId: post-some-schema
  parameters: []
  requestBody:
    description: "SomeSchema path request body"
    content:
      application/json:
        schema:
          $ref: "../root.yaml#components/schemas/SomeSchema"
  responses:
    "200":
      description: "SomeSchema path response"
      content:
      application/json:
        schema:
          $ref: "../root.yaml#components/schemas/SomeSchema"

Final notes:
I attached two zip files with a full working example of the current and proposed behavior. I thought it may help to see the full file/path structure. I tested both of them and they both validate and render correctly for me.

The only issue that I can think of is when referencing a sub-section of a schema. For example, if the property from schema A references a property from Schema B. The reference $ref: "schemas/AnotherSchema.yaml#properties/aProperty" works correctly while using the proposed method reference $ref: "../../root.yaml#components/schemas/AnotherSchema/properties/aProperty" does not. I am not sure if there is a workaround at the moment.

current-openapi-format-split-example.zip
proposed-openapi-format-split-example.zip