Fix (some) SwiftLint violations

[erwald]

Checklist

• Updated CHANGELOG.md.

This PR adds the .swiftlint.yml config file, and runs swiftlint autocorrect to fix some issues. Mind, there are still 740 violations left (of which 601 are classified as "serious").

I disabled the opening_braces rule because it didn't like arrays of closures, like this:

let expectations: [(String) -> Void] = [
  { event in expect(event) == "[] value 1" },
  { event in expect(event) == "[] completed" },
  { event in expect(event) == "[] terminated" },
  { event in expect(event) == "[] disposed" }
]

Maybe some other rules need to be disabled as well, such as the tuple size and identifier name length rules.

[andersio]

It doesn’t need to be in changelog, since it is not relevant to the public API.

[erwald]

I suspected as much. Fixed!

[mdiep]

Can we change this rule? By default SwiftLint enforces no trailing comma. I think we should enforce the trailing comma. This tends to make diffs more readable and merges easier since adding a line doesn't alter the previously last item in the array.

[erwald]

Makes sense. I added the exception and reinserted the commas.

[mdiep]

Instead of disabling it, you can actually require the comma by adding this at the top level:

trailing_comma:
  mandatory_comma: true

Would you mind doing that instead? Sorry that wasn't clear before. 😅

[erwald]

Ah-ha! Done and done.

[erwald]

Not quite sure why the Linux build fails – it seems Test Case 'XCTestCase.MutableProperty, should not deadlock' started at 18:02:17.226 does, in fact, deadlock.

But I'm not sure how this PR could affect that. Are the tests sometimes unstable, by any chance?

[mdiep]

I think that particular test is unstable. I've rerun those tests—hopefully they'll pass this time.