`express.static.mime` is not exported in Express 5.x

[mxxk]

Description

Express 4.x used to export the mime transitive dependency as express.static.mime:

• express@4.21.2 exported serve-static
• serve-static@1.16.2 exported send.mime
• send@0.19.0 exported mime

Express 5.x no longer provides this export, but its documentation still references it:

The newer version send@1.1.0 no longer exports mime, so I'm not sure if this would be considered a documentation issue with Express 5.x, or a bug (which would require changes to serve-static and send). Would you please confirm?

Expectations

If this is considered a documentation issue, here is a proposed revision to the documentation of res.type(type) which would remedy the inconsistency:

 If `type` contains the “/” character, then it sets the `Content-Type` to the
 exact value of `type`, otherwise it is assumed to be a file extension and the
 MIME type is looked up
-in a mapping using the `express.static.mime.lookup()` method.
+using the `lookup` method of the `mime-types` package.

[dpopp07]

I believe this is an oversight in the documentation, as those exports were explicitly removed. Unless I'm corrected, I'll go ahead and make a change to the docs. Thanks for the suggested revision!

Edit: the contentType() method is used under the hood, so I'll amend your suggestion:

express/lib/response.js

Line 497 in af7cd90

? (mime.contentType(type) || 'application/octet-stream')

[wesleytodd]

I think these are the two relevant commits. Unfortunately I do not see these being denoted as breaking changes in any of the changelogs. This is likely an oversight but IMO this is a good change as exporting an entire dependency's api like this is generally never a good idea. Not only should we update the docs shown, we should also probably backtrack to add it to the change log and migration guide.

expressjs/serve-static@50cc670
pillarjs/send@889d310

@dpopp07, is that something you are interested in doing? If so, we can try and fast track those changes so they land before we go latest. If not, let me know and I can take a look at them this week.

[dpopp07]

@wesleytodd Yep, I'm happy to and should be able to work on it today.

Not only should we update the docs shown, we should also probably backtrack to add it to the change log and migration guide.

I already opened expressjs/expressjs.com#1783 to address the docs changes. I'll open something separate to retrofit the changelog/migration guide.

[dpopp07]

I updated the above PR to include the migration guide changes.

PRs for updating the changelogs:

• serve-static: docs: retroactively note 2.0.0-beta.1 api change in history file serve-static#194
• express: docs: retroactively note 5.0.0-beta.1 api change in history file #6333

The changelog for send already notes the export removal, which seems sufficient so I didn't make a change there.

• Use mime-types for file to content type mapping -- removed send.mime

I think that's everything!