Reader changes external reference

[richardkaspar]

Describe the bug
Microsoft.OpenApi.Readers 1.3.2 changes external references, that contains the character #.
The behavior of Microsoft.OpenApi.Readers 1.2.3 is as expected. It does not change external references. I did not check other Versions.
Example:
Reference in the OpenAPI file: https://gigantic-server.com/schemas/Monster#/?id=foo
After reading: https://gigantic-server.com/schemas/Monster#/components/schemas//?id=foo

To Reproduce
Use the following code to read 'readFile' and write 'writeFile'.
Open the two files in a compare tool.
Code:

        using var stream = new FileStream(readFile, FileMode.Open);
        var doc =
            new OpenApiStreamReader(
                    new OpenApiReaderSettings
                    {
                        ReferenceResolution = ReferenceResolutionSetting.DoNotResolveReferences
                    })
               .Read(stream, out _);

        var sb = new StringBuilder();

        var writer = new OpenApiYamlWriter(new StringWriter(sb, new CultureInfo("en_us")));

        doc.SerializeAsV3(writer);

        File.WriteAllText(writeFile, sb.ToString());

readFile:

    openapi: 3.0.1
    info:
      title: anyOf-oneOf
      license:
        name: MIT
      version: 1.0.0
    paths: { }
    components:
      schemas:
        Nested:
          type: object
          properties:
            AnyOf:
              anyOf:
                - $ref: '#/components/schemas/OneOf'
                - $ref: file:///C:/MySchemas.json#/definitions/ArrayObject
                - $ref: https://gigantic-server.com/schemas/Monster#/?id=foo
                - $ref: '#/components/schemas/ExtRef'
            OneOf:
              oneOf:
                - $ref: ../foo/schemas.yaml#/components/schemas/Number
                - $ref: '#/components/schemas/ExtRef'
                - $ref: '#/components/schemas/AnyOf'
                - type: string
        OneOf:
          oneOf:
            - $ref: ../foo/schemas.yaml#/components/schemas/Number
            - $ref: file:///C:/MySchemas.json#/definitions/ArrayObject
            - $ref: https://gigantic-server.com/schemas/Monster#/?id=foo
            - $ref: '#/components/schemas/ExtRef'
            - $ref: '#/components/schemas/AnyOf'
            - type: string
        AnyOf:
          anyOf:
            - $ref: '#/components/schemas/OneOf'
            - $ref: ../foo/schemas.yaml#/components/schemas/Number
            - $ref: file:///C:/MySchemas.json#/definitions/ArrayObject
            - $ref: https://gigantic-server.com/schemas/Monster#/?id=foo
            - $ref: '#/components/schemas/ExtRef'
        ExtRef:
          $ref: https://www.mid.de/OpenAPI/Schema/foo#/

writeFile:

    openapi: 3.0.1
    info:
      title: anyOf-oneOf
      license:
        name: MIT
      version: 1.0.0
    paths: { }
    components:
      schemas:
        Nested:
          type: object
          properties:
            AnyOf:
              anyOf:
                - $ref: '#/components/schemas/OneOf'
                - $ref: file:///C:/MySchemas.json#/components/schemas//definitions/ArrayObject
                - $ref: https://gigantic-server.com/schemas/Monster#/components/schemas//?id=foo
                - $ref: '#/components/schemas/ExtRef'
            OneOf:
              oneOf:
                - $ref: ../foo/schemas.yaml#/components/schemas/Number
                - $ref: '#/components/schemas/ExtRef'
                - $ref: '#/components/schemas/AnyOf'
                - type: string
        OneOf:
          oneOf:
            - $ref: ../foo/schemas.yaml#/components/schemas/Number
            - $ref: file:///C:/MySchemas.json#/components/schemas//definitions/ArrayObject
            - $ref: https://gigantic-server.com/schemas/Monster#/components/schemas//?id=foo
            - $ref: '#/components/schemas/ExtRef'
            - $ref: '#/components/schemas/AnyOf'
            - type: string
        AnyOf:
          anyOf:
            - $ref: '#/components/schemas/OneOf'
            - $ref: ../foo/schemas.yaml#/components/schemas/Number
            - $ref: file:///C:/MySchemas.json#/components/schemas//definitions/ArrayObject
            - $ref: https://gigantic-server.com/schemas/Monster#/components/schemas//?id=foo
            - $ref: '#/components/schemas/ExtRef'
        ExtRef:
          $ref: https://www.mid.de/OpenAPI/Schema/foo#/components/schemas//

Expected behavior
The content of writeFile and readFile should be equal.

Screenshots/Code Snippets

Additional context

[darrelmiller]

Thank you for reporting this. This issue seems to be as a result of us adding support for inlining external references to OpenAPI descriptions. We currently don't support external references to files that are not OpenAPI descriptions (what we call fragments). However, we should not be changing the URL to external files that are fragments. I will investigate.