bug: Incorrectly strips index from content collection root index page

[techfg]

When a content collection has a page in the root (e.g., /collection/index.md), the slug should remain index unless there is a custom slug defined and if the custom slug is empty string (``), it should be treated as a directory reference and resulting url contain a / at end. For subdirectories (e.g., `/collection/subdir/index.md`), index should be stripped.

Found this issue and confirmed behavior that Astro itself does not strip index for root pages in a collection unless custom slug is defined.

Repro:

• https://stackblitz.com/edit/withastro-astro-7ge5gz

With Proposed Fixes from PR #21:

• https://stackblitz.com/edit/withastro-astro-mtqt5k

Steps to reproduce:

1. Open repro
2. Click on Post 1 link
3. Click on Go to Other Stuff Index under Repro for Issue #16

Expected Behavior:
Link should navigate to /otherstuff/index

Actual Behavior:
index is stripped and link results in 404

4. Go back to Post 1
5. Hover over (or inspect via dev console) the link for Go to Posts Index

Expected Behavior:
Link should be /posts/ since it contains a custom slug of empty string ('')

Actual Behavior:
Link is /posts without the trailing slash

Additional Info:

1. Clicking on Go to Other Stuff Subdir Index works as index is properly stripped
2. Clicking on Go to Posts Index works but the url is wrong (see step 4 & 5) - The existing code does a boolean compare on slug to determine if a custom slug exists but empty string evaluates to false so its treated as not having a custom slug
3. Clicking on Go to Other Stuff 2 Index works as a custom slug of myindex is defined and it is properly detected and transformed
4. You can see all links that Astro generates on home page under Issue #16 heading
5. Related: Special case handling of index files was added in Process index.md files correctly + add contentPath option #3 based on Does not work with index pages #2

[techfg]

FYI - Edited OP to a Stackblitz to the repro that contains the proposed fixes from #21.

[vernak2539]

Released in v0.9.0! Thanks!