[Bug] Markdown xref broken for external xrefmap.yml

[glopesdev]

This is a regression in 2.76.0. Confirmed that the same reference resolves fine in 2.75.3 so we are downgrading for the time being.

Markdown cross-references in articles pointing to UIDs defined in external xrefmap.yml files are resolved as if they are internal API references. For example:

[OtherClass](xref:External.Namespace.OtherClass) will resolve to http://mydomain.org/api/External.Namespace.OtherClass.html instead of http://externaldomain.org/api/External.Namespace.OtherClass.html.

To Reproduce
Steps to reproduce the behavior:

1. Add xref section to docfx.json containing a URL to a xrefmap.yml in another domain.
2. Add a markdown cross-reference to a UID in the external YML file.

Expected behavior
Cross-references should resolve to links pointing to the external website.

Context (please complete the following information):

• OS: Windows
• Docfx version: [e.g. 2.76.0]

Additional context
Downgrading to 2.75.3 fixes the problem.

[filzrev]

@glopesdev
Are you using redirection entry in xrefmap.json?.
If so. it'll be fixed by #9832. (Fix wrong XRefMapRedirection.cs Href attribute that introduced)

It's expected be released same timing with #9824 changes.
But it's not merged yet. (Because I've mixed bugfix in perf optimization PR)

If it's not using redirection entry.
It's expected to be caused by #9824 changes.

Please provide example xrefmap that cause problems.

[glopesdev]

@filzrev this doesn't use redirection (or at least not intentionally. I didn't even know this feature existed until now), both projects use mostly default docfx settings.

Example xrefmap: https://horizongir.github.io/ZedGraph/xrefmap.yml

[filzrev]

@glopesdev
Where is the externaldomain setting is defined?

It seems xrefmap define href as relative URL. and no baseUrl setting is defined.
So it's expected behaviors that are resolved to mydomain based URL.

[glopesdev]

@filzrev I have updated the issue to clarify that externaldomain is part of the example resolved URL, and not a setting. The external websites and xrefmap.yml were generated by DocFX built with default settings.

So it's expected behaviors that are resolved to mydomain based URL.

I am not sure I understand the rationale for this. These are not local xrefmap.yml files, they are added as external additional references using a URL which is outside of the domain, so why should they be assumed to be part of the local project?

Also if this is the case then there is a breaking change which should be documented more clearly since as I mentioned in the issue the behavior changes if we downgrade to 2.75.3 where these external references are resolved correctly to the external website URL.

[filzrev]

Thanks for your reply.

I've confirmed it can reproduce problems when specify xrefmap with URLs.

It's regression introduced by my PR commit.
And it occurred when following conditions met.

1. Specify xrefmap with URL
2. Xrefmap don't define baseUrl. And using relative URL for href.

---

Previous implementation converting all hrefs when file is downloaded.
And my PR commit changes this behaviors. (Changes to rewrite URL on docfx download command)

I'll create fix PR later as soon as possible with relating tests.
Sorry for any inconvenience caused by regression.