Add rule: no_multiline_collapse

[kj6dev]

Overview

Never collapse multi-line code into a single line to meet line limits. The fix is always to extract into a named subview/property.

Rule Identifier

no_multiline_collapse

Rationale

Collapsing multi-line code into a single line destroys readability. Line limits exist to encourage extraction, not compression.

Example

// ORIGINAL - triggered skimmable_body warning
@ViewBuilder private var presetButtons: some View {
    if !config.presets.isEmpty {
        HStack {
            ForEach(config.presets.indices, id: \.self) { index in
                presetButton(at: index)
            }
        }
    }
}

// ❌ BAD "fix" - cramming code to reduce line count
@ViewBuilder private var presetButtons: some View {
    if !config.presets.isEmpty {
        HStack {
            ForEach(config.presets.indices, id: \.self) { presetButton(at: $0) }
        }
    }
}

// ✅ GOOD fix - extract complexity
@ViewBuilder private var presetButtons: some View {
    if !config.presets.isEmpty {
        presetButtonsRow
    }
}

private var presetButtonsRow: some View {
    HStack {
        ForEach(config.presets.indices, id: \.self) { index in
            presetButton(at: index)
        }
    }
}

Detection Challenge

Hard to detect programmatically - this is more of a code review principle. Could potentially detect:

• Lines significantly longer than surrounding code
• Closures with complex expressions crammed onto one line
• { $0.something } patterns that could be expanded

Notes

May be better as skill/guidance than automated rule. Consider implementing as a "suggestion" level rather than warning/error.

Priority

High (as guidance), Medium (as automated rule)