Deriving mime type inconsistent with Go 1.17

[cubic3d]

Looks like Go 1.17 changed the source for mime types (golang/go#46013) it's no longer sources from mailcap using /etc/mime.types but from the Shared MIME-Info Database at /usr/share/mime/.

So if I use the official build from current version 2.4.3 and request a file from localhost/file.ign I get the correct header Content-Type: application/vnd.coreos.ignition+json. Building the same version with xcaddy with Go 1.17 will not set a content type because application/vnd.coreos.ignition+json is not part of the shared database on my system it looks like. More popular types like text/plain work fine.

Is there a way to make the lookup more consistent and remove the external dependency? Maybe embedding mime types in the Caddy binary?

[francislavoie]

Hmm. No, Caddy doesn't have anything built-in for overriding MIME types right now.

I think you should open an issue upstream to report this problem, since this is a regression that they introduced.

I would expect that if no MIME type is found in your shared DB, then it should fallback to /etc/mime.types 🤔

The specific PR that made the change is golang/go#45271

[francislavoie]

You may also want to consider asking https://gitlab.freedesktop.org/xdg/shared-mime-info to add that mime type to the database.

[mholt]

Think I'm going to close this, as it seems that having the MIME db properly installed on the system should resolve the issue; not really a Caddy bug. Thanks!