fix: check if endpoint exists for dynamic pages when checking for red…

[VitaliyR]

…irect

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Summary

Fixes WRFL-2122

Basically we are checking only for static files when trying to determinate if we should do the non forced redirect.

In dynamic SSG, when they either run in dev mode or having dynamic endpoints (not a static files), we are not detecting it and doing the redirect, which is wrong.

I've added a simple checker via fetch url, { method: HEAD } - which checks if the endpoint exists.

Example

Assume next netlify.toml:

[[redirects]]
from = "*"
to = "https://www.netlify.app/:splat"
status = 200
force = false # by default

Run netlify dev.

Make change to some code file.

Open http://localhost:8888. See that change is not applied. See in console Proxying to https://www.netlify.app/.

Thats wrong, it should actually detect that there is an index route in current site and not proxy.

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[github-actions]

📊 Benchmark results

Comparing with 1ff368f

• Dependency count: 1,201 (no change)
• Package size: 316 MB (no change)
• Number of ts-expect-error directives: 830 (no change)

[VitaliyR]

@smnh you added this, but when there is transfer-encoding, you should not send content-length.
sindresorhus/got#1576

WDYT about this change?

[smnh]

According to MDN, It looks like it should be ommitted only when Transfer-Encoding is chunked.
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Transfer-Encoding#syntax

And it make sense, because for regular non chunked encodings like gzip and deflate you do want to have content-length.

if (proxyResHeaders['transfer-encoding']?.includes('chunked') {
  ...
}