add link_checker settings for external_level and internal_level

[mwcz]

Based on this convo.

This PR adds new link checker configuration settings: internal_level and external_level, which can both be set to "warn" or "error". The current behavior of zola is to always error on broken internal links and on external links with unparsable URLs, so these new settings allow those to be treated as warnings instead. In other words, it allows zola to build sites even though they have broken links. The current behavior is still the default.

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[Keats]

Why that change? It should be equivalent to bail!

[mwcz]

I made that change so it doesn't bail on the first unparseable URL. It tries to parse everything, and then if there were any failures, it prints out all the unparseable URLs and then bails.

[mwcz]

I'm happy to reverse that change though, I can see how bailing on the first error is more consistent and leads to less complexity.

[Keats]

but I believe the code of get_link_domain before and the one with your changes is exactly the same no? You're just returning the error either way in get_link_domain

It's fine to report all of them though

[mwcz]

Whoops, for some reason I was under the impression that bail caused an immediate panic. Whoops, I'll change it back.

[Keats]

Sorry for writing so much, this PR has gone down several different paths and I'm trying to get my bearings.

No worries!
I was thinking about it today as well and my thoughts might be a bit out of scope for the PR.

What if the link checker was not using Errors but was instead using a Vec<String> string for the errors.
This way we can build the error message ourselves nicely, something like:

Failed to build the site
Error: Found 3 broken anchor links
  1. The anchor in the link `@/post.md#foo` in content/post.md does not exist.
  2. The anchor in the link `@/post.md#bar` in content/post.md does not exist.
  3. The anchor in the link `@/post.md#baz` in content/post.md does not exist.

We can/should obviously apply the same kind of .formatting to external link errors obviously.
What do you think?

[mwcz]

I can imagine check_external_links and check_internal_links_with_anchors emitting a Vec<String> which contains the text for all the errors or warnings that were encountered. Those functions are called from site/src/lib.rs, so I suppose that's where the logging could happen. Seems like a clean solution; the logging code would only need to exist in site/src/lib.rs instead of being duplicated at every early-return site. It would potentially change the ordering of error/warning logs relative to regular printlns since the errors/warnings would be delayed until the function returns, but the link checker hardly has any printlns so I don't see a problem there. Seems good to me, so I guess I'll give it a try next week.

[mwcz]

The internal link checking that happens in markdown.rs would need a similar treatment I suppose, so the code would be more-or-less duplicated, but only in two places. 🤔

[Keats]

Yes the markdown one is unfortunate... maybe keep it as is for now and see if it feels odd when trying it out.

[mwcz]

It seems pretty good. The markdown.rs link checking errors/warnings aren't formatted exactly the same, but it doesn't feel odd when using zola. Here's a demo.

https://asciinema.org/a/Ructp25lMiFB1ztSatUr74ASn

[Keats]

Sweet thanks

[Keats]

FYI I just pushed a commit to make the external link checking a bit more DRY: 1a3b783