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Cache source lines in vertical_parameter_alignment #6865

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Cache source lines in vertical_parameter_alignment #6865

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7 changes: 6 additions & 1 deletion Source/SwiftLintBuiltInRules/Rules/Style/VerticalParameterAlignmentRule.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,11 @@ struct VerticalParameterAlignmentRule: Rule {

private extension VerticalParameterAlignmentRule {
final class Visitor: ViolationsSyntaxVisitor<ConfigurationType> {
// Computed once per file: `SourceLocationConverter.sourceLines` materializes every line of the
// file as a new `[String]` on each access, and `graphemeColumn(line:column:)` below reads it
// once per parameter, which is quadratic in the size of the file.
private lazy var sourceLines = locationConverter.sourceLines

@SimplyDanny SimplyDanny Aug 8, 2026

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We could also have this cached as part of SwiftLintFile+Cache to make it available to all rules.


override func visitPost(_ node: FunctionDeclSyntax) {
violations.append(contentsOf: violations(for: node.signature.parameterClause.parameters))
}
Expand Down Expand Up @@ -52,7 +57,7 @@ private extension VerticalParameterAlignmentRule {
/// by multi-byte characters (e.g. a non-ASCII function name) are compared by their visible alignment
/// rather than by their byte offset.
private func graphemeColumn(line: Int, column: Int) -> Int {
guard let graphemeClusters = String(locationConverter.sourceLines[line - 1].utf8.prefix(column - 1)) else {
guard let graphemeClusters = String(sourceLines[line - 1].utf8.prefix(column - 1)) else {
return column
}
return graphemeClusters.count + 1
Expand Down