Rule request: Empty lines in function bodies

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• Updated SwiftLint to the latest version
• I searched for existing GitHub issues

Rule Request

Description

Each method should fulfill only one goal, therefore, it should not contain any "parts". If you see that the code blocks in your method beg for logical separation - do not separate these blocks using an empty line, instead, refactor your method by splitting it into several ones or create a new class.

Read:
An Empty Line is a Code Smell,
Adoption of a custom checkstyle rule

What would trigger?

// Notice empty line in the method body
internal func exceedsLineCountExcludingCommentsAndWhitespace(_ start: Int, _ end: Int, _ limit: Int) -> (Bool, Int) {
        guard end - start > limit else {
            return (false, end - start)
        }

        let count = end - start - numberOfCommentAndWhitespaceOnlyLines(startLine: start, endLine: end)
        return (count > limit, count)
    }

What would not trigger?

internal func exceedsLineCountExcludingCommentsAndWhitespace(_ start: Int, _ end: Int, _ limit: Int) -> (Bool, Int) {
        guard end - start > limit else {
            return (false, end - start)
        }
        let count = end - start - numberOfCommentAndWhitespaceOnlyLines(startLine: start, endLine: end)
        return (count > limit, count)
    }

Configurable?

The rule should not be configurable.

Opt-in or enabled?

This rule could be a personal preference or coding style from various individuals, so it could be kept as opt-in.

Start by reviewing SwiftLint's existing rule implementations and tests to find the entry point for an opt-in rule that inspects empty lines inside function bodies. Use the triggering and non-triggering examples in this issue to define the expected behavior, and consider the rule complete when those cases are detected correctly without configuration.