Add --list option that outputs names of files changed

[ArturGajowy]

Currently, running:

scalafmt Foo.scala

on a non-formatted file outputs:

Reformatting...

I'd expect it to list all the files that were changed during reformatting, or provide an option to do so.

Similarly, running:

scalafmt --test Foo.scala

will output the diffs of files needing formatting - but ideally there'd be an option to just list the names.

[tanishiking]

It would be nice for scalafmt to list all the formating files (if scalafmt receives the list of files to format) without any options 👍

[ArturGajowy]

Not sure if I understand: so if run
scalafmt Foo.scala Bar.scala
and only Foo.scala changes due to formatting, what would be the output?

If I just run:
scalafmt
and that changes just Foo.scala - what would be the the output?

I'm not sure if you mean the outputs to be:

1. Foo.scala in both cases
2. Foo.scala and Bar.scala in the first case, nothing in the second case

?

[tanishiking]

• scalafmt Foo.scala Bar.scala
  • it should print Foo.scala and Bar.scala because those two files are the target (even if Bar.scala doesn't have any change by scalafmt)
• scalafmt
  • it shouldn't show any filenames in any cases.

[ArturGajowy]

That would be useful debugging info, but would not help my use case - I'd like to see the files that changed (when running without --test) or need changing (when running with --test). So I'm after option 1. above.

Maybe there should be two flags: --list and --list-not-formatted?

[mroth]

Also strong want this, and suspect my use case is the same as @ArturGajowy -- I want a list of all files that "would be re-formatted". In my case, it's because we want to run this in CI, and warn if a file was not scalafmt'd. The standard "diff" format is useful for writing changes to a file, but not as an error message.

For comparison, similar options with other formatters:

• prettier --check (https://prettier.io/docs/en/cli.html#check)
• gofmt -l (-l list files whose formatting differs from gofmt's)

In the case of Prettier, you then get output such as:

Checking formatting...
src/fileA.js
src/fileB.js
Code style issues found in the above file(s). Forgot to run Prettier?

This is a much nicer error message to give someone in a failed CI check than dumping many screens of diffs.

[tanishiking]

I want a list of all files that "would be re-formatted".

Ah, finally I got it.
It would be nice to have an option --list or something whose behavior is equivalent to gofmt -l (list files whose formatting differs from scalafmt's)

[tanishiking]

Closed by #1466 👍