In my Swift codebase, I put brackets on newlines in some specific cases due to my poor vision. I want to enforce this rule using SwiftLint.

My requirements are simple:

• Show a warning when the character { is on the same line as the following strings:

  • func, if, else, class, struct, catch, try, init, guard, switch

I’m far from a REGEX expert, but I came up with this REGEX string: ^(?=.*{)(?=.*(?:func|if|else|class|struct|catch|try|init|guard|switch)).*$

The rule ends up looking like this:

custom_rules:
  brackets_newline:
      name: "Opening Brackets not on Next Line"
      message: "Opening brackets should be placed on their own lines"
      include: "*.swift"
      regex: '^(?=.*{)(?=.*(?:func|if|else|class|struct|catch|try|init|guard|switch)).*$'
      severity: warning

Now, in a REGEX playground, this works well with no problems. Try this file, for example: https://pastebin.ai/urmb1ejoly

However, when I run SwiftLint on this file in Xcode, it produces the brackets_newline warning on top of any Swift file, even if it has no violation of the brackets_newline rule:

I tried excluding lines starting with the characters //, but that just shifts the error to the first empty line.

I’m expecting the rule violation warning to show up only on the relevant lines.

What am I doing wrong?