maven IDE hook for jj fix

[victornoel]

Hi,

I am trying to setup jujutsu so that it runs spotless (configured using the maven plugin in my repository) when using jj fix, see https://jj-vcs.github.io/jj/latest/cli-reference/#jj-fix.

The problem is that the requirement from jujutsu is that the tool that does formatting should respect the following rule:

The external tools must accept the current file content on standard input, and return the updated file content on standard output. A tool's output will not be used unless it exits with a successful exit code. Output on standard error will be passed through to the terminal.

Would that be something that could be added to spotless?

Thanks!

[nedtwigg]

Spotless Gradle supports this, but the Maven support is immature. @SapiensAnatis has made some progress here.

[SapiensAnatis]

I didn’t write the IDE hook to be clear, but it sounds broadly like what you are looking for.

If you use these arguments: https://github.com/SapiensAnatis/vscode-spotless-maven/blob/5cb5fa5a1cc444e47aa50e33547b2ffefdf56dec/src/maven/basicMavenExecutor.ts#L28

You will get a process that takes a document on stdin and then returns on stderr IS CLEAN / IS DIRTY and on stdout the formatted document.

The only problem is I can’t remember if you get the formatted document on stdout if Spotless returns IS CLEAN. In the vscode extension we just return ‘no changes’ if we get that back.

[victornoel]

Hey @SapiensAnatis @nedtwigg thank you for the feedback, I will do a bit of experimentation with that to see how it behaves and come back here to share my findings!

[victornoel]

I can already share this:

• on "IS CLEAN", the file is not outputted indeed, that could be a problem for jj fix but I'm sure I will find a temporary workaround until we decide here if we should change the behaviour or not
• on "IS DIRTY" it looks like it's doing exactly what I am expecting
• in the long run there will also be the concern of performance
  • mvn is slow to startup, so for tens of file it's going to be long to run… well, it's always better than doing it by hand 😃
  • I'm not sure how this can be solved in practice: I mean, spotless already starts a separate npm process to be able to format multiple files faster, now will we need a separate mvn process to submit the files to format? 😅

[SapiensAnatis]

Performance wise I think the way forward is to use mvnd which runs as a daemon and is much faster for ad-hoc formatting. However it doesn’t seem to be compatible with the IDE hook at the minute, I’ve raised a few issues over there so hopefully those will be fixed soon!

[victornoel]

I did a few tests with mvnd using both -DspotlessFiles and -DspotlessIdeHook (without stdin/out) and performances are still not great

It's taking something like 2.8sec with -DspotlessFiles and 3.8sec with -DspotlessIdeHook. The IDE Hook actually restarts the npm process every time ^^

running spotless:apply on ALL my files takes the same time btw, so the overhead is somewhere else, which means there is maybe some margin for improvement on the spotless side :)

[SapiensAnatis]

Oh the IDE hook is really only for a single file (hence IDE). On a single file it takes about 0.4s for me (assuming the daemon is warm) but if you are formatting your entire solution it will probably be slower.