fix: include route prefix in vercel func names, fix #8401

[slawekkolodziej]

Changes

Recently updated Vercel adapter has a bug. If two routes have identical file names but different directory structures, the adapter will produce only one serverless function and assign it to both routes.

This PR fixes the problem.

Some more details: #8401

Testing

Within vercel adapter I created 'serverless-with-dynamic-routes' fixture and added necessary tests. If you run those tests against current main, the will fail.

Docs

No need to update docs. This PR only fixes a rather major bug and brings the expected behavior.

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[slawekkolodziej]

Since my proposed change injects route path to file name, I begun to wonder what is the maximum allowed length for serverless function name in Vercel build output? Since I couldn't find the answer in their documentation, I had to run some manual tests.

The answer is: less than 240 characters. If *.func folder has 240 characters or more, Vercel responds with

Error: ENAMETOOLONG: name too long

With that in mind, I think that the proposed solution is fine for the time being, just to fix the original issue. However ideally there should be a mechanism that limits function name length.

[matoous]

thought: should we at least throw an error if the length is exceeded? Other option would be to hash the path into fixed-size string and use only the filename, e.g. src/api/some-endpoint-path-here/sub-folder-there/another-subfolder-here/and-we-keep-nesting-forever-and-ever/until-we-get-to/the-final-file.ts would be f526d3493c217e4aaf128fa1cb0f553de92cf30fce348a2b00231c8638fa9626.the-final-file.ts (although this make it way less readable and harder to debug) (the hash length could be reduced).

[slawekkolodziej]

I thought about limiting the file name to a sane number of characters and adding short content hash to the end.

I like to have route included in the function name - as you said, it simplifies debugging and makes debug.

Now when I think about it, we could ditch entry- and -astro parts of function names completely, to improve monitoring even more:

Consider what my original change generates:

After some adjustments, Vercel can accept this too:

[ematipico]

Now when I think about it, we could ditch entry- and -astro parts of function names completely

• entry comes from the core; maybe we should remove it from there?
• .astro is just the extension of the file, you would need to remove .js, .ts, etc., right?

[slawekkolodziej]

• .astro is just the extension of the file, you would need to remove .js, .ts, etc., right?

The complete file extension is .astro.mjs, original code already removed .mjs.

[slawekkolodziej]

I simplified the code a bit, now my routes looks as clean as they can get 💚

[ematipico]

I left some comments. I think overall, we could release this fix.