Allow output when fixes are automatically applied

Observed in eslint 3.8.1

Right now if you run with --fix and eslint only finds fixable issues, it will output nothing and exit with code 0.

However, it may have caused changes to your files on disk. Developers might not notice this. We’ve found some problems where developers will run eslint and then push to Github, without catching that changes have been applied locally.

Is it currently possible to output messages for fixes that have been automatically applied? Or some other way of differentiating between “everything is good” vs. “there were errors but they were fixed”. I’m happy to put together a PR for this if this functionality does not exist.

[ilyavolodin]

I honestly think that this issue should be moved out of 4.0 and into the next milestone. It doesn’t have an implementation yet, and it doesn’t even look like we are settled on a way to do this. I would rather not rush a solution just to get it into a release. There’s nothing stopping us from doing another major release in a month or two.

[not-an-aardvark]

This seems like a reasonable change. However, in terms of reporting the actual number of fixes, I’m worried about overestimating the number of fixed problems due to the way multi-pass autofixing works.

For example, here’s some code:

/* eslint quote-props: [error, "always"], quotes: [error, "single"] */

({ foo: 1 })

First, the quote-props fixer is applied:

({ "foo": 1 })

Then ESLint is run again on the resulting code, to ensure fix any other linting errors that might have been output. In this case, a new error with quotes has been created, so another fix will be applied:

({ 'foo': 1 })

Then ESLint is run again on the resulting code. No errors are reported, so the process exits.

In this scenario, how many fixes were applied? Technically, 2 fixes were applied, but it might be confusing if we output something like 2 problems fixed, or ``quote-propsandquotes fixed problems, because the original code only had one problem. The second fix was only necessary as a result of the first fix.

I still think this change is doable, but if the message is going to be anything more detailed than some things were fixed, we should think about how we can convey that without confusion.