Support prerender in Netlify redirects

[matthewp]

Changes

• Fixes [Prerender] Pages with dynamic routes in the same folder don't work in @2.0.0-beta.2 #5860
• A little bit of a refactor of the logic that generates the _redirects file to be a little more structured.
• Rather than use the build-generated "distURL", which is always going to be wrong for dynamic routes, builds it itself and uses Netlify's placeholder syntax. For spread routes it uses the * syntax.
• Prettifys it a bit so that each part, the input, target, and status all line up.

Testing

• Test added for the same scenario that the bug describes.

Docs

N/A, bug fix.

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[bluwy]

Ah I see what needs to be fixed now. I tested this locally, I wonder if the functions/fixtures/404/dist/_redirects is correct now though. It is:

/*      /.netlify/functions/entry    404
/       /.netlify/functions/entry    200
/404    /.netlify/functions/entry    200

where the /* is the first and I think that causes a 404 always? Before this PR it's:

  /    /.netlify/functions/entry    200
  /404    /.netlify/functions/entry    200
  /*    /.netlify/functions/entry    404

I think we need to sort to like before for this case.

[matthewp]

Ah yeah, you're right. I think I was actually wrong about needing to sort dynamic routes first. What you really want is to sort any exact route first. It's the wildcard/spread routes that need to come last. I think I'll add a specificity integer and sort that way. I'll add a test for this too.

[natemoo-re]

Will these conflict? I expect that they might and only /pets/:cat would be matched.

Since all of these are generating actual files we might need to track any files that the dynamic route has generated, then add redirects for the exact route?

expect(redir).to.include('/pets/cat1       /pets/cat1/index.html        200');
expect(redir).to.include('/pets/cat2       /pets/cat2/index.html        200');
expect(redir).to.include('/pets/cat3       /pets/cat3/index.html        200');
expect(redir).to.include('/pets/dog1       /pets/dog1/index.html        200');
expect(redir).to.include('/pets/dog2       /pets/dog2/index.html        200');
expect(redir).to.include('/pets/dog3       /pets/dog3/index.html        200');

[matthewp]

They do conflict in an SSR context but in SSG since they are pre-generated they are just redundant. Meaning Netlify is going to use the first one and ignore the second; but that doesn't matter because it will go to the right file anyways.

The user should probably combine these into 1 route, but we don't require that at the moment so this is a valid (if odd) way to split up different "types" of data in SSG.

[matthewp]

Ok, I think I got it now @bluwy here: 00224f3

The changes are:

• Astro already sorts the route array so we don't need to resort what is produced for _redirects.
• But, the wildcard 404 route is the exception. Since this is a new route that we create we need to sort it. So this change gives it a lower weight so its always sorted last. This is what you want, any defined routes are hit and then there's a final wildcard 404.