Support decoding link summaries with absolute paths to external pages

[d-ronnqvist]

Bug/issue #, if applicable: rdar://149470919

Summary

Support decoding link summaries from external documentation sources that use absolute paths.

This for exa please allows interfacing with another documentation system that hosts its pages on a different domain.

Dependencies

None.

Testing

• Modify the bin/test-data-external-resolver script on line 95 to return an absolute web URL for the page.

• Set the DOCC_LINK_RESOLVER_EXECUTABLE environment to the path to the bin/test-data-external-resolver script

• Build some documentation with a link to <doc://com.test.bundle/something> in the content.

• Preview the documentation.

  • The link on the web page should have the full absolute web URL from the bin/test-data-external-resolver script.

Checklist

Make sure you check off the following items. If they cannot be completed, provide a reason.

• Added tests
• Ran the ./bin/test script and it succeeded
• Updated documentation if necessary

[d-ronnqvist]

@swift-ci please test

[anferbui]

Verified it works as expected together with swift-docc-render locally 👍🏻

[d-ronnqvist]

@swift-ci please test

[mayaepps]

@d-ronnqvist Could this property be made public to match the rest of this struct? It doesn't make sense to me that a client of DocC's API could access all the other properties in this structure except this one.

[d-ronnqvist]

It does make sense to have API that only DocC can use but that clients can't.

In this case I'm not sure yet if this property fits into the long-term design of linking between documentation and unless we have an explicit need for making it public (in which case I would probably say we should only make it SPI) I would really prefer to not commit to its long term existence.

This type (LinkDestinationSummary) is used for both documentation from other documentation sources (resolved via a separate process) and documentation from other DocC targets (resolved via --dependency arguments). DocC itself doesn't produce any summaries with absolute presentation URLs but we can't make any guarantees about what other documentation systems do.

At this point I would rather not have behaviors of other documentation systems impact the design for DocC's own external documentation information.