Only show swiftpm errors for current file.

[merisbahti]

The ale linter shows errors for files that aren't open, this can be confusing - especially when the linter shows an error that really doesn't exist in the current open files buffer.

[keith]

Hmm. I think this behavior is desired since we're not really linting. If you change a protocol in the only file you have open and break all consumers, that seems like useful info. Let me check what other Ale linters like this do.

[merisbahti]

You're right, it is practical, however the problem is when the output is confusing, see this picture for info:
https://imgur.com/a/RWkLSo4

It's saying that in the current file Eval.swift, there's this error:
cannot convert value of type 'Int' to expected argument type 'String' which isn't right at all.

Usually I only use the linter to see the problems in the current file, and do a swift build to see the holistic perspective. swiftlint works the same way.

[keith]

Ah interesting, it seems like the incorrect file name in the list is the issue we should fix, instead of filtering the errors all together. Do you know why that is happening?