Add a CLI command to output the config that shall be used for a given file

[bradzacher]

Recently I made a change to Canva's dprint config so that we used dprint-plugin-ruff to format our python code. However I didn't realise that I had accidentally turned off all python formatting in the codebase with my change because I'd forgotten to add associations to the config.

When I ran the formatter with --verbose I saw dprint instantiate dprint-plugin-ruff and it looked like it formatted all of the files.
But it turned out that without associations dprint was only running isort (via dprint-plugin-exec) on the files.

It wasn't until a python dev let me know that their code had violated line length without being formatted did we realise my mistake.

It would be great if there was a way to dump the config for a specific file to help validate that everything is setup as expected. I'd expect such a command to resolve all associations and includes/excludes and dump just the expected configs for the plugins that will be run.

For example eslint has --print-config <file> which will do all of the config resolution and work until just before the lint run actually starts and then prints the config and exits.

[dsherret]

There is already a dprint output-resolved-config sub command. Perhaps that could accept a file path as well and the returned config would be limited to only the plugins being formatted. I'm not sure if it should just be another arg or most likely a flag (not sure about a name).

By the way, what I always do to test that is just open a file, add some spaces, then re-run the formatter.

[bradzacher]

Yeah in hindsight that's what I should have done. And is what I did to verify my fix actually fixed things.

I just ran dprint with verbose mode and saw it had python files and the format time was sane and I stopped there.

And because the codebase was already formatted there ofc weren't CI failures.

Now that I've correctly configured it I can see dprint outputs logs differently if two plugins are running on a file!

Yeah I tried using output-resolved-config but because the plugin is actually configured it shows up there. The issue was that it wasn't associated with python files. Tricky nuance to the config!