Add RedundantStringEnumValueRule

CHANGELOG.md

@@ -21,6 +21,11 @@
 
 * Add `EmojiReporter`: a human friendly reporter.  
   [Michał Kałużny](https://github.com/justMaku)
+
+* Add `redundant_string_enum_value` rule that warns against String enums
+  with redundant value assignments.  
+  [Marcelo Fabri](https://github.com/marcelofabri)
+  [#946](https://github.com/realm/SwiftLint/issues/946)
 
 ##### Bug Fixes
 

Source/SwiftLintFramework/Models/MasterRuleList.swift

@@ -75,6 +75,7 @@ public let masterRuleList = RuleList(rules:
     PrivateOutletRule.self,
     PrivateUnitTestRule.self,
     RedundantNilCoalescingRule.self,
+    RedundantStringEnumValueRule.self,
     ReturnArrowWhitespaceRule.self,
     StatementPositionRule.self,
     SwitchCaseOnNewlineRule.self,

Source/SwiftLintFramework/Rules/RedundantStringEnumValueRule.swift

@@ -0,0 +1,141 @@
+//
+//  RedundantStringEnumValueRule.swift
+//  SwiftLint
+//
+//  Created by Marcelo Fabri on 08/12/16.
+//  Copyright © 2016 Realm. All rights reserved.
+//
+
+import Foundation
+import SourceKittenFramework
+
+private func children(of dict: [String: SourceKitRepresentable],
+                      matching kind: SwiftDeclarationKind) -> [[String: SourceKitRepresentable]] {
+    return (dict["key.substructure"] as? [SourceKitRepresentable] ?? []).flatMap { item in
+        if let subDict = item as? [String: SourceKitRepresentable],
+            let kindString = subDict["key.kind"] as? String,
+            SwiftDeclarationKind(rawValue: kindString) == kind {
+                return subDict
+        }
+        return nil
+    }
+}
+
+public struct RedundantStringEnumValueRule: ASTRule, ConfigurationProviderRule {
+    public var configuration = SeverityConfiguration(.warning)
+
+    public init() {}
+
+    public static let description = RuleDescription(
+        identifier: "redundant_string_enum_value",
+        name: "Redudant String Enum Value",
+        description: "String enum values can be omitted when they are equal to the enumcase name.",
+        nonTriggeringExamples: [
+            "enum Numbers: String {\n case one\n case two\n}\n",
+            "enum Numbers: Int {\n case one = 1\n case two = 2\n}\n",
+            "enum Numbers: String {\n case one = \"ONE\"\n case two = \"TWO\"\n}\n",
+            "enum Numbers: String {\n case one = \"ONE\"\n case two = \"two\"\n}\n",
+            "enum Numbers: String {\n case one, two\n}\n"
+        ],
+        triggeringExamples: [
+            "enum Numbers: String {\n case one = ↓\"one\"\n case two = ↓\"two\"\n}\n",
+            "enum Numbers: String {\n case one = ↓\"one\", two = ↓\"two\"\n}\n",
+            "enum Numbers: String {\n case one, two = ↓\"two\"\n}\n"
+        ]
+    )
+
+    public func validateFile(_ file: File,
+                             kind: SwiftDeclarationKind,
+                             dictionary: [String: SourceKitRepresentable]) -> [StyleViolation] {
+        guard kind == .enum else {
+            return []
+        }
+
+        // Check if it's a String enum
+        let inheritedTypes = (dictionary["key.inheritedtypes"] as? [SourceKitRepresentable])?
+            .flatMap({ ($0 as? [String: SourceKitRepresentable]) as? [String: String] })
+            .flatMap({ $0["key.name"] }) ?? []
+        guard inheritedTypes.contains("String") else {
+            return []
+        }
+
+        let violations = violatingOffsetsForEnum(dictionary: dictionary, file: file)
+        return violations.map {
+            StyleViolation(ruleDescription: type(of: self).description,
+                           severity: configuration.severity,
+                           location: Location(file: file, byteOffset: $0))
+        }
+    }
+
+    private func violatingOffsetsForEnum(dictionary: [String: SourceKitRepresentable],
+                                         file: File) -> [Int] {
+        var caseCount = 0
+        var violations = [Int]()
+
+        for enumCase in children(of: dictionary, matching: .enumcase) {
+            caseCount += enumElementsCount(dictionary: enumCase)
+            violations += violatingOffsetsForEnumCase(dictionary: enumCase, file: file)
+        }
+
+        guard violations.count == caseCount else {
+            return []
+        }
+
+        return violations
+    }
+
+    private func enumElementsCount(dictionary: [String: SourceKitRepresentable]) -> Int {
+        return children(of: dictionary, matching: .enumelement).filter({ element in
+            return !filterEnumInits(dictionary: element).isEmpty
+        }).count
+    }
+
+    private func violatingOffsetsForEnumCase(dictionary: [String: SourceKitRepresentable],
+                                             file: File) -> [Int] {
+        return children(of: dictionary, matching: .enumelement).flatMap { element -> [Int] in
+            guard let name = element["key.name"] as? String else {
+                return []
+            }
+            return violatingOffsetsForEnumElement(dictionary: element, name: name, file: file)
+        }
+    }
+
+    private func violatingOffsetsForEnumElement(dictionary: [String: SourceKitRepresentable],
+                                                name: String,
+                                                file: File) -> [Int] {
+        let enumInits = filterEnumInits(dictionary: dictionary)
+
+        return enumInits.flatMap { dictionary -> Int? in
+            guard let offset = (dictionary["key.offset"] as? Int64).flatMap({ Int($0) }),
+                let length = (dictionary["key.length"] as? Int64).flatMap({ Int($0) }) else {
+                    return nil
+            }
+
+            // the string would be quoted if offset and length were used directly
+            let enumCaseName = file.contents.substringWithByteRange(start: offset + 1,
+                                                                    length: length - 2) ?? ""
+            guard enumCaseName == name else {
+                return nil
+            }
+
+            return offset
+        }
+    }
+
+    private func filterEnumInits(dictionary: [String: SourceKitRepresentable]) ->
+                                                                [[String: SourceKitRepresentable]] {
+        guard let elements = dictionary["key.elements"] as? [SourceKitRepresentable] else {
+            return []
+        }
+
+        let enumInitKind = "source.lang.swift.structure.elem.init_expr"
+        return elements.flatMap { element in
+            guard let dict = element as? [String: SourceKitRepresentable],
+                dict["key.kind"] as? String == enumInitKind else {
+                    return nil
+            }
+
+            return dict
+        }
+    }
+}

SwiftLint.xcodeproj/project.pbxproj

@@ -73,6 +73,7 @@
 		D0E7B65319E9C6AD00EDBA4D /* SwiftLintFramework.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D0D1216D19E87B05005E4BAA /* SwiftLintFramework.framework */; };
 		D0E7B65619E9C76900EDBA4D /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0D1211B19E87861005E4BAA /* main.swift */; };
 		D40F83881DE9179200524C62 /* TrailingCommaConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = D40F83871DE9179200524C62 /* TrailingCommaConfiguration.swift */; };
+		D41E7E0B1DF9DABB0065259A /* RedundantStringEnumValueRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D41E7E0A1DF9DABB0065259A /* RedundantStringEnumValueRule.swift */; };
 		D4348EEA1C46122C007707FB /* FunctionBodyLengthRuleTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4348EE91C46122C007707FB /* FunctionBodyLengthRuleTests.swift */; };
 		D43DB1081DC573DA00281215 /* ImplicitGetterRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D43DB1071DC573DA00281215 /* ImplicitGetterRule.swift */; };
 		D44254201DB87CA200492EA4 /* ValidIBInspectableRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D442541E1DB87C3D00492EA4 /* ValidIBInspectableRule.swift */; };
@@ -277,6 +278,7 @@
 		D0D1217D19E87B05005E4BAA /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		D0E7B63219E9C64500EDBA4D /* swiftlint.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = swiftlint.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		D40F83871DE9179200524C62 /* TrailingCommaConfiguration.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = TrailingCommaConfiguration.swift; sourceTree = "<group>"; };
+		D41E7E0A1DF9DABB0065259A /* RedundantStringEnumValueRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = RedundantStringEnumValueRule.swift; sourceTree = "<group>"; };
 		D4348EE91C46122C007707FB /* FunctionBodyLengthRuleTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FunctionBodyLengthRuleTests.swift; sourceTree = "<group>"; };
 		D43DB1071DC573DA00281215 /* ImplicitGetterRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ImplicitGetterRule.swift; sourceTree = "<group>"; };
 		D442541E1DB87C3D00492EA4 /* ValidIBInspectableRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ValidIBInspectableRule.swift; sourceTree = "<group>"; };
@@ -664,6 +666,7 @@
 				B2902A0B1D66815600BFCCF7 /* PrivateUnitTestRule.swift */,
 				094385021D5D4F78009168CF /* PrivateOutletRule.swift */,
 				24B4DF0B1D6DFA370097803B /* RedundantNilCoalescingRule.swift */,
+				D41E7E0A1DF9DABB0065259A /* RedundantStringEnumValueRule.swift */,
 				E57B23C01B1D8BF000DEA512 /* ReturnArrowWhitespaceRule.swift */,
 				3BCC04CE1C4F56D3006073C3 /* RuleConfigurations */,
 				692B60AB1BD8F2E700C7AA22 /* StatementPositionRule.swift */,
@@ -1014,6 +1017,7 @@
 				3BB47D851C51D80000AE6A10 /* NSRegularExpression+SwiftLint.swift in Sources */,
 				E881985B1BEA974E00333A11 /* StatementPositionRule.swift in Sources */,
 				B58AEED61C492C7B00E901FD /* ForceUnwrappingRule.swift in Sources */,
+				D41E7E0B1DF9DABB0065259A /* RedundantStringEnumValueRule.swift in Sources */,
 				E88DEA711B09847500A66CB0 /* ViolationSeverity.swift in Sources */,
 				B2902A0C1D66815600BFCCF7 /* PrivateUnitTestRule.swift in Sources */,
 				3BD9CD3D1C37175B009A5D25 /* YamlParser.swift in Sources */,

Tests/SwiftLintFrameworkTests/RulesTests.swift

@@ -229,6 +229,10 @@ class RulesTests: XCTestCase {
         verifyRule(RedundantNilCoalescingRule.description)
     }
 
+    func testRedundantStringEnumValue() {
+        verifyRule(RedundantStringEnumValueRule.description)
+    }
+
     func testReturnArrowWhitespace() {
         verifyRule(ReturnArrowWhitespaceRule.description)
     }