Add only configuration option to todo rule

CHANGELOG.md

@@ -12,7 +12,10 @@
 
 #### Enhancements
 
-* None.
+* Add `only` configuration option to `todo` rule which allows to specify
+  whether the rule shall trigger on `TODO`s, `FIXME`s or both.  
+  [gibachan](https://github.com/gibachan)
+  [#5233](https://github.com/realm/SwiftLint/pull/5233)
 
 #### Bug Fixes
 

Source/SwiftLintBuiltInRules/Rules/Lint/TodoRule.swift

@@ -2,7 +2,7 @@ import Foundation
 import SwiftSyntax
 
 struct TodoRule: SwiftSyntaxRule, ConfigurationProviderRule {
-    var configuration = SeverityConfiguration<Self>(.warning)
+    var configuration = TodoConfiguration()
 
     static let description = RuleDescription(
         identifier: "todo",
@@ -26,41 +26,55 @@ struct TodoRule: SwiftSyntaxRule, ConfigurationProviderRule {
     )
 
     func makeVisitor(file: SwiftLintFile) -> ViolationsSyntaxVisitor {
-        Visitor(viewMode: .sourceAccurate)
+        Visitor(todoKeywords: configuration.only)
     }
 }
 
 private extension TodoRule {
     final class Visitor: ViolationsSyntaxVisitor {
+        private let todoKeywords: [TodoConfiguration.TodoKeyword]
+
+        init(todoKeywords: [TodoConfiguration.TodoKeyword]) {
+            self.todoKeywords = todoKeywords
+            super.init(viewMode: .sourceAccurate)
+        }
+
         override func visitPost(_ node: TokenSyntax) {
-            let leadingViolations = node.leadingTrivia.violations(offset: node.position)
-            let trailingViolations = node.trailingTrivia.violations(offset: node.endPositionBeforeTrailingTrivia)
+            let leadingViolations = node.leadingTrivia.violations(offset: node.position,
+                                                                  for: todoKeywords)
+            let trailingViolations = node.trailingTrivia.violations(offset: node.endPositionBeforeTrailingTrivia,
+                                                                    for: todoKeywords)
             violations.append(contentsOf: leadingViolations + trailingViolations)
         }
     }
 }
 
 private extension Trivia {
-    func violations(offset: AbsolutePosition) -> [ReasonedRuleViolation] {
+    func violations(offset: AbsolutePosition,
+                    for todoKeywords: [TodoConfiguration.TodoKeyword]) -> [ReasonedRuleViolation] {
         var position = offset
         var violations = [ReasonedRuleViolation]()
         for piece in self {
-            violations.append(contentsOf: piece.violations(offset: position))
+            violations.append(contentsOf: piece.violations(offset: position, for: todoKeywords))
             position += piece.sourceLength
         }
         return violations
     }
 }
 
 private extension TriviaPiece {
-    func violations(offset: AbsolutePosition) -> [ReasonedRuleViolation] {
+    func violations(offset: AbsolutePosition,
+                    for todoKeywords: [TodoConfiguration.TodoKeyword]) -> [ReasonedRuleViolation] {
         switch self {
         case
                 .blockComment(let comment),
                 .lineComment(let comment),
                 .docBlockComment(let comment),
                 .docLineComment(let comment):
-            let matches = regex(#"\b((?:TODO|FIXME)(?::|\b))"#)
+
+            // Construct a regex string considering only keywords.
+            let searchKeywords = todoKeywords.map(\.rawValue).joined(separator: "|")
+            let matches = regex(#"\b((?:\#(searchKeywords))(?::|\b))"#)
                 .matches(in: comment, range: comment.bridge().fullNSRange)
             return matches.reduce(into: []) { violations, match in
                 guard let annotationRange = Range(match.range(at: 1), in: comment) else {

Source/SwiftLintBuiltInRules/Rules/RuleConfigurations/TodoConfiguration.swift

@@ -0,0 +1,31 @@
+import SwiftLintCore
+
+struct TodoConfiguration: SeverityBasedRuleConfiguration, Equatable {
+    typealias Parent = TodoRule
+
+    enum TodoKeyword: String, CaseIterable, AcceptableByConfigurationElement {
+        case todo = "TODO"
+        case fixme = "FIXME"
+
+        func asOption() -> OptionType { .symbol(rawValue) }
+    }
+
+    @ConfigurationElement(key: "severity")
+    private(set) var severityConfiguration = SeverityConfiguration<Parent>(.warning)
+    @ConfigurationElement(key: "only")
+    private(set) var only = TodoKeyword.allCases
+
+    mutating func apply(configuration: Any) throws {
+        guard let configuration = configuration as? [String: Any] else {
+            throw Issue.unknownConfiguration(ruleID: Parent.identifier)
+        }
+
+        if let severityString = configuration[$severityConfiguration] as? String {
+            try severityConfiguration.apply(configuration: severityString)
+        }
+
+        if let onlyStrings = configuration[$only] as? [String] {
+            self.only = onlyStrings.compactMap { TodoKeyword(rawValue: $0) }
+        }
+    }
+}

Tests/SwiftLintFrameworkTests/TodoRuleTests.swift

@@ -20,8 +20,28 @@ class TodoRuleTests: SwiftLintTestCase {
         XCTAssertEqual(violations.first!.reason, "FIXMEs should be resolved (Implement)")
     }
 
-    private func violations(_ example: Example) -> [StyleViolation] {
-        let config = makeConfig(nil, TodoRule.description.identifier)!
+    func testOnlyFixMe() {
+        let example = Example("""
+            fatalError() // TODO: Implement todo
+            fatalError() // FIXME: Implement fixme
+        """)
+        let violations = self.violations(example, config: ["only": ["FIXME"]])
+        XCTAssertEqual(violations.count, 1)
+        XCTAssertEqual(violations.first!.reason, "FIXMEs should be resolved (Implement fixme)")
+    }
+
+    func testOnlyTodo() {
+        let example = Example("""
+            fatalError() // TODO: Implement todo
+            fatalError() // FIXME: Implement fixme
+        """)
+        let violations = self.violations(example, config: ["only": ["TODO"]])
+        XCTAssertEqual(violations.count, 1)
+        XCTAssertEqual(violations.first!.reason, "TODOs should be resolved (Implement todo)")
+    }
+
+    private func violations(_ example: Example, config: Any? = nil) -> [StyleViolation] {
+        let config = makeConfig(config, TodoRule.description.identifier)!
         return SwiftLintFrameworkTests.violations(example, config: config)
     }
 }