99 lines
4.7 KiB
Swift
99 lines
4.7 KiB
Swift
import SwiftSyntax
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struct DiscardedNotificationCenterObserverRule: SwiftSyntaxRule, ConfigurationProviderRule, OptInRule {
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var configuration = SeverityConfiguration(.warning)
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static let description = RuleDescription(
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identifier: "discarded_notification_center_observer",
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name: "Discarded Notification Center Observer",
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description: "When registering for a notification using a block, the opaque observer that is " +
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"returned should be stored so it can be removed later",
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kind: .lint,
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nonTriggeringExamples: [
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Example("let foo = nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil) { }\n"),
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Example("""
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let foo = nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil, using: { })
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"""),
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Example("func foo() -> Any {\n" +
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" return nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil, using: { })\n" +
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"}\n"),
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Example("var obs: [Any?] = []\n" +
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"obs.append(nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil, using: { }))\n"),
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Example("""
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var obs: [String: Any?] = []
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obs["foo"] = nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil, using: { })
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"""),
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Example("var obs: [Any?] = []\n" +
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"obs.append(nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil, using: { }))\n"),
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Example("func foo(_ notif: Any) {\n" +
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" obs.append(notif)\n" +
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"}\n" +
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"foo(nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil, using: { }))\n"),
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Example("""
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var obs: [NSObjectProtocol] = [
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nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil, using: { }),
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nc.addObserver(forName: .CKAccountChanged, object: nil, queue: nil, using: { })
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]
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""")
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],
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triggeringExamples: [
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Example("↓nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil) { }\n"),
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Example("_ = ↓nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil) { }\n"),
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Example("↓nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil, using: { })\n"),
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Example("""
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@discardableResult func foo() -> Any {
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return ↓nc.addObserver(forName: .NSSystemTimeZoneDidChange, object: nil, queue: nil, using: { })
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}
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""")
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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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}
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private extension DiscardedNotificationCenterObserverRule {
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final class Visitor: ViolationsSyntaxVisitor {
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override func visitPost(_ node: FunctionCallExprSyntax) {
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guard
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let calledExpression = node.calledExpression.as(MemberAccessExprSyntax.self),
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case .identifier("addObserver") = calledExpression.name.tokenKind,
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case let argumentLabels = node.argumentList.map({ $0.label?.text }),
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argumentLabels.starts(with: ["forName", "object", "queue"])
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else {
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return
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}
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if
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let firstParent = node.parent?.as(ReturnStmtSyntax.self),
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let secondParent = firstParent.parent?.as(CodeBlockItemSyntax.self),
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let thirdParent = secondParent.parent?.as(CodeBlockItemListSyntax.self),
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let fourthParent = thirdParent.parent?.as(CodeBlockSyntax.self),
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let fifthParent = fourthParent.parent?.as(FunctionDeclSyntax.self),
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!fifthParent.attributes.hasDiscardableResultAttribute
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{
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return // result is returned from a function
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} else if node.parent?.is(TupleExprElementSyntax.self) == true {
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return // result is passed as an argument to a function
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} else if node.parent?.is(ArrayElementSyntax.self) == true {
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return // result is an array literal element
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} else if
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let previousToken = node.previousToken,
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case .equal = previousToken.tokenKind,
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previousToken.previousToken?.tokenKind != .wildcard
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{
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return // result is assigned to something other than the wildcard keyword (`_`)
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}
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violations.append(node.positionAfterSkippingLeadingTrivia)
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}
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}
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}
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private extension AttributeListSyntax? {
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var hasDiscardableResultAttribute: Bool {
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contains(attributeNamed: "discardableResult")
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}
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}
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