Support fix option

[kui]

Add gulpEslint.outputFixes which write fixed contents to the files.

For example:

gulp.src('js/**/*.js')
    .pipe(eslint({ fix: true })
    .pipe(eslint.outputFixes())
    .pipe(eslint.format())

[shinnn]

No tests.

[kui]

@shinnn
Sorry about that. I added tests.

[adametry]

I appreciate the PR and tests; however, I'm not certain of the approach. Since gulp is basically streaming transformation tool, I believe it would be better to apply the fix to file.contents and use standard gulp.dest to write to disk.

I've recently published a release candidate that includes support for the "fix" option (among other things). This pre-release version can be installed using the "rc" tag, like so:

npm install gulp-eslint@rc

If you could, try it out and see if the following approach works for you:

var gulp = require('gulp');
var eslint = require('gulp-eslint');
gulp.task('lint-fix', function () {
    return gulp.src('js/**/*.js')
        .pipe(eslint({ fix: true }))
        .pipe(eslint.format())
        .pipe(gulp.dest('./'));
});

Alternatively, here's a version that writes only writes files that eslint fixed, using gulp-if:

var gulp = require('gulp');
var eslint = require('gulp-eslint');
var gulpIf = require('gulp-if');
function isFixed(file) {
    return file.eslint && typeof file.eslint.output === 'string';
}
gulp.task('lint-fix', function () {
    return gulp.src('js/**/*.js')
        .pipe(eslint({ fix: true }))
        .pipe(eslint.format())
        .pipe(gulpIf(isFixed, gulp.dest('./')));
});

By folding the fix to the gulp stream, it leaves the possibility for additional linting, transforms, concatenation, etc. Besides, with eslint able to "fix" source now, it's becoming a transformation tool (like a rule-based browserify-lite).

[kui]

@adametry
I think it's the better way than my patch. I'll close this.
But I want your answer before @shinnn's comment if possible. I misunderstood that this patch will be merged. I found that the tests were required by coveralls.
Thanks.

[grssam]

Hi, I am using the rc version like this:

function isFixed(file) {
  return file.eslint && typeof file.eslint.output === 'string';
}

gulp.task("lint", function() {
  return gulp.src("js/**/*.js")
    .pipe(eslint({
      fix: true,
      rules: {
        "no-multi-spaces": 2,
        "indent": [2, 2, {"SwitchCase": 1}]
      }
    }))
    .pipe(eslint.formatEach())
    .pipe(eslint.failAfterError())
    .pipe(gulpIf(isFixed, gulp.dest("./")));
});

When I run gulp lint, it does nothing - Neither does it fix the indentation or multiple spaces, nor does it output the errors on console. If I make fix as false, it reports the errors correctly. failAfterError has no effect.

[grssam]

And I found the issue - in gulp.dest you need to give the base directory. So in my case (and in the case of the example provided), it should be gulp.dest("js")