fix: Provide correct mime type for javascript and css

[Artur-]

The correct mimetype for javascript is a requirement when loading javascript modules

[deki]

@Artur- Agree that this needs to be fixed. I've changed the implementation to be more generic instead of hard-coding two types. Could you please have a look?

[Artur-]

It does not seem to work for me. Files.probeContentType returns null for a filename like /VAADIN/build/app.afe73ca6.js

[deki]

Hmm can you replicate that in your testcase? Because that succeeds with the implementation...

[Artur-]

It works on my local JVM, fails when deployed

[deki]

Hmm ok did some more testing:

• Corretto 8.362.08.1 - fail
• Corretto 11.0.18.10.1 - success
• Corretto 17.0.6.10.1 - success

Which runtime are you using?

[Artur-]

[deki]

Ok I was able to reproduce it. Looks like the method is highly platform specific but I want to avoid pulling in another library like Apache Tika to solve it.
Will get in touch with our Lambda team internally...

[deki]

Made another change, this implementation should be close to what you proposed (using the filename to guess the context type).

[Artur-]

Still does not work in my case:

With file being e.g. /VAADIN/build/react.8caaa40e.js I see
mimeTypes.getContentType(file): application/octet-stream
mimeTypeGuess: null

and the result is then application/octet-stream

[deki]

It turned out the related mailcap package is present on Amazon Linux but not part of the Lambda managed runtime. Still waiting for feedback from our service team, afterwards we'll make a decision on how to fix it.

[Artur-]

Any luck in couple of months? :)

[deki]

Our Lambda service team confirmed they will fix it but I can't tell a date yet.

Afterwards /etc/mime.types will be present and https://github.com/corretto/corretto-11/blob/b99712f303f94fffcb8af283e80a3c71f9a1ae0b/src/java.base/linux/classes/sun/nio/fs/LinuxFileSystemProvider.java#L107 will work as designed.

[deki]

Starting with 2.0 we return null instead of application/octet-stream if content type cannot be resolved (as per servlet-api docs), a fix to make probeContentType work in Lambda execution environment is being worked on by the Lambda service team.
I opened #562 to improve test coverage.

[deki]

The Java 21 managed runtime that was just released contains the necessary fix to make probeContentType work as well.