Fix: relative references in subdirectory documents are not loading #1674

[dldl-cmd]

Use OpenApiDocuments BaseUri as location of the document. This allows to have during loading further documents a base Url for retrieval, which can be combined with a relative Uri to get an absolute.
Fixes #1674

[baywet]

Thanks for the contribution!

@MaggieKimani1 can you do an initial review here please?

[MaggieKimani1]

@dldl-cmd sorry for the delay in response/review.
I have checked out the issue that this PR resolves and it seems that this is by design.
Have you considered creating a custom external refs loader, an implementation of our IStreamLoader interface as per Darrel's comment here?
Our default stream reader class is a bit limited as file/resource location might vary depending on use case, hence the exposed interface that you can use to resolve the relative references for documents contained in subdirectories, and pass the custom loader as part of the OpenApiReaderSettings as shown here

OpenAPI.NET/test/Microsoft.OpenApi.Readers.Tests/OpenApiWorkspaceTests/OpenApiWorkspaceStreamTests.cs

Line 53 in ff287bc

CustomExternalLoader = new ResourceLoader(),

Once you do so, the files will automatically be registered with the source document's workspace.

Reference:

OpenAPI.NET/test/Microsoft.OpenApi.Readers.Tests/OpenApiWorkspaceTests/OpenApiWorkspaceStreamTests.cs

Lines 85 to 98 in ff287bc

	public class ResourceLoader : IStreamLoader
	{
	public Stream Load(Uri uri)
	{
	return null;
	}
	public Task<Stream> LoadAsync(Uri uri, CancellationToken cancellationToken = default)
	{
	var path = new Uri(new("http://example.org/V3Tests/Samples/OpenApiWorkspace/"), uri).AbsolutePath;
	path = path[1..]; // remove leading slash
	return Task.FromResult(Resources.GetStream(path));
	}
	}

[dldl-cmd]

@MaggieKimani1 implementing just an own stream loader cannot solve the problem. The reason is, that the stream loader has no idea, which document is the current parent and where this document is located. Therefore it cannot resolve the relative reference as it doesn't know to which location it is relative. An example:

• root.yaml

....
$ref: ./DirA/DirB/DirC/second.yaml#/components/schema/Second

• DirA/DirB/DirC/second.yaml

...
$ref: ../third.yaml#/components/schema/Third

• DirA/DirB/third.yaml

...
$ref: ./DirC/Fourth.yaml#/components/schema/Fourth.yaml

When the reference $ref: ./DirC/Fourth.yaml#/components/schema/Fourth.yaml should be resolved. It is necessary to known that this reference is relative to the document at DirA/DirB/third.yaml.

This information is not only necessary at the time of loading the document but also when OpenApiDocument.ResolveReference tries to resolve a reference.