Fixes regression on routing priority for multi-layer index pages

[Fryuni]

Changes

The sorting algorithm positions more specific routes before less specific routes, and considers index pages to be more specific than a dynamic route with a rest parameter inside of it.
This means that /blog is considered more specific than /blog/[...slug].

But this special case was being applied incorrectly to indexes, which could cause a problem in scenarios like the following:

• /
• /blog
• /blog/[...slug]

The algorithm would make the following comparisons:

• / is more specific than /blog (incorrect)
• /blog/[...slug] is more specific than / (correct)
• /blog is more specific than /blog/[...slug] (correct)

Although the incorrect first comparison is not a problem by itself, it could cause the algorithm to make the wrong decision.
Depending on the other routes in the project, the sorting could perform just the last two comparisons and by transitivity infer the inverse of the third (/blog/[...slug > / > /blog), which is incorrect.

Now the algorithm doesn't have a special case for index pages and instead does the comparison soleley for rest parameter segments and their immediate parents, which is consistent with the transitivity property.

• Closes Issue in Astro 4.2.4+ with dynamic routes ordering #10071

Testing

• Added the reproduction scenario from Issue in Astro 4.2.4+ with dynamic routes ordering #10071
• Added an extra case in an existing test
• Changed some of the tests to verify the expected relation invariants instead of the full order of the routes to make mistakes easier to spot and to understand in error reports
• Changes the order of one test case that was inconsistent with our rules

Docs

No docs changes expected :)

[changeset-bot]

🦋 Changeset detected

Latest commit: bc61b1b

The changes in this PR will be included in the next version bump.

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR