88 lines
3.3 KiB
Swift
88 lines
3.3 KiB
Swift
import SwiftSyntax
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struct RedundantDiscardableLetRule: SwiftSyntaxCorrectableRule, ConfigurationProviderRule {
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var configuration = SeverityConfiguration(.warning)
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init() {}
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static let description = RuleDescription(
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identifier: "redundant_discardable_let",
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name: "Redundant Discardable Let",
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description: "Prefer `_ = foo()` over `let _ = foo()` when discarding a result from a function",
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kind: .style,
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nonTriggeringExamples: [
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Example("_ = foo()\n"),
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Example("if let _ = foo() { }\n"),
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Example("guard let _ = foo() else { return }\n"),
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Example("let _: ExplicitType = foo()"),
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Example("while let _ = SplashStyle(rawValue: maxValue) { maxValue += 1 }\n"),
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Example("async let _ = await foo()")
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],
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triggeringExamples: [
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Example("↓let _ = foo()\n"),
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Example("if _ = foo() { ↓let _ = bar() }\n")
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],
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corrections: [
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Example("↓let _ = foo()\n"): Example("_ = foo()\n"),
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Example("if _ = foo() { ↓let _ = bar() }\n"): Example("if _ = foo() { _ = bar() }\n")
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]
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)
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func makeVisitor(file: SwiftLintFile) -> ViolationsSyntaxVisitor {
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Visitor(viewMode: .sourceAccurate)
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}
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func makeRewriter(file: SwiftLintFile) -> ViolationsSyntaxRewriter? {
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Rewriter(
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locationConverter: file.locationConverter,
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disabledRegions: disabledRegions(file: file)
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)
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}
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}
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private extension RedundantDiscardableLetRule {
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final class Visitor: ViolationsSyntaxVisitor {
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override func visitPost(_ node: VariableDeclSyntax) {
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if node.hasRedundantDiscardableLetViolation {
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violations.append(node.positionAfterSkippingLeadingTrivia)
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}
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}
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}
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final class Rewriter: SyntaxRewriter, ViolationsSyntaxRewriter {
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private(set) var correctionPositions: [AbsolutePosition] = []
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let locationConverter: SourceLocationConverter
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let disabledRegions: [SourceRange]
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init(locationConverter: SourceLocationConverter, disabledRegions: [SourceRange]) {
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self.locationConverter = locationConverter
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self.disabledRegions = disabledRegions
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}
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override func visit(_ node: VariableDeclSyntax) -> DeclSyntax {
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guard
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node.hasRedundantDiscardableLetViolation,
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!node.isContainedIn(regions: disabledRegions, locationConverter: locationConverter)
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else {
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return super.visit(node)
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}
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correctionPositions.append(node.positionAfterSkippingLeadingTrivia)
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let newNode = node
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.with(\.bindingKeyword, .keyword(.let, presence: .missing))
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.with(\.bindings, node.bindings.with(\.leadingTrivia, node.bindingKeyword.leadingTrivia))
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return super.visit(newNode)
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}
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}
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}
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private extension VariableDeclSyntax {
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var hasRedundantDiscardableLetViolation: Bool {
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bindingKeyword.tokenKind == .keyword(.let) &&
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bindings.count == 1 &&
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bindings.first!.pattern.is(WildcardPatternSyntax.self) &&
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bindings.first!.typeAnnotation == nil &&
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modifiers?.contains(where: { $0.name.text == "async" }) != true
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}
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}
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