Added hash_value_overflow rule

CHANGELOG.md

@@ -24,6 +24,11 @@
   for large files.  
   [Niil Öhlin](https://github.com/niilohlin)
 
+* Add new opt-in rule `hash_function` to warn against empty wrong hashValue
+  implementation.
+  [Kim de Vos](https://github.com/kimdv)
+  [#2108](https://github.com/realm/SwiftLint/issues/2108)
+
 #### Bug Fixes
 
 * Fix false positives in `redundant_objc_attribute` for private declarations

Rules.md

@@ -54,6 +54,7 @@
 * [Function Default Parameter at End](#function-default-parameter-at-end)
 * [Function Parameter Count](#function-parameter-count)
 * [Generic Type Name](#generic-type-name)
+* [Hash Function](#hash-function)
 * [Identical Operands](#identical-operands)
 * [Identifier Name](#identifier-name)
 * [Implicit Getter](#implicit-getter)
@@ -7980,6 +7981,94 @@ enum Foo<↓type> {}
 
 
 
+## Hash Function
+
+Identifier | Enabled by default | Supports autocorrection | Kind | Analyzer | Minimum Swift Compiler Version
+--- | --- | --- | --- | --- | ---
+`hash_function` | Enabled | No | lint | No | 4.2.0 
+
+Prefer using implementation `hash(into:)` instead of `hashValue`
+
+### Examples
+
+<details>
+<summary>Non Triggering Examples</summary>
+
+```swift
+struct Foo: Hashable {
+    let bar: Int = 10
+
+    func hash(into hasher: inout Hasher) {
+        hasher.combine(bar)
+      }
+}
+```
+
+```swift
+class Foo: Hashable {
+    let bar: Int = 10
+
+    func hash(into hasher: inout Hasher) {
+        hasher.combine(bar)
+      }
+}
+```
+
+```swift
+var hashValue: Int { return 1 }
+class Foo: Hashable { 
+ }
+```
+
+```swift
+class Foo: Hashable {
+    let bar: String = "Foo"
+
+    public var hashValue: String {
+        return bar
+    }
+}
+```
+
+```swift
+class Foo: Hashable {
+    let bar: String = "Foo"
+
+    public var hashValue: String {
+        get { return bar }
+        set { bar = newValue }
+    }
+}
+```
+
+</details>
+<details>
+<summary>Triggering Examples</summary>
+
+```swift
+struct Foo: Hashable {
+    let bar: Int = 10
+
+    public ↓var hashValue: Int {
+        return bar
+    }
+}
+```
+
+```swift
+class Foo: Hashable {
+    let bar: Int = 10
+
+    public ↓var hashValue: Int {
+        return bar
+    }
+}
+```
+
+</details>
+
+
+
 ## Identical Operands
 
 Identifier | Enabled by default | Supports autocorrection | Kind | Analyzer | Minimum Swift Compiler Version

Source/SwiftLintFramework/Extensions/Configuration+Merging.swift

@@ -61,8 +61,8 @@ extension Configuration {
             return type(of: lhs.rule).description.identifier == type(of: rhs.rule).description.identifier
         }
 
-        fileprivate var hashValue: Int {
-            return type(of: rule).description.identifier.hashValue
+        public func hash(into hasher: inout Hasher) {
+            hasher.combine(type(of: rule).description.identifier)
         }
     }
 

Source/SwiftLintFramework/Extensions/NSRegularExpression+SwiftLint.swift

@@ -9,8 +9,8 @@ private struct RegexCacheKey: Hashable {
 }
 
 extension NSRegularExpression.Options: Hashable {
-    public var hashValue: Int {
-        return rawValue.hashValue
+    public func hash(into hasher: inout Hasher) {
+        hasher.combine(rawValue)
     }
 }
 

Source/SwiftLintFramework/Models/Configuration.swift

@@ -22,15 +22,18 @@ public struct Configuration: Hashable {
     public private(set) var configurationPath: String? // if successfully loaded from a path
     public let cachePath: String?
 
-    public var hashValue: Int {
+    public func hash(into hasher: inout Hasher) {
         if let configurationPath = configurationPath {
-            return configurationPath.hashValue
+            hasher.combine(configurationPath)
         } else if let rootPath = rootPath {
-            return rootPath.hashValue
+            hasher.combine(rootPath)
         } else if let cachePath = cachePath {
-            return cachePath.hashValue
+            hasher.combine(cachePath)
+        } else {
+            hasher.combine(included)
+            hasher.combine(excluded)
+            hasher.combine(reporter)
         }
-        return (included + excluded + [reporter]).reduce(0, { $0 ^ $1.hashValue })
     }
 
     internal var computedCacheDescription: String?

Source/SwiftLintFramework/Models/MasterRuleList.swift

@@ -55,6 +55,7 @@ public let masterRuleList = RuleList(rules: [
     FunctionDefaultParameterAtEndRule.self,
     FunctionParameterCountRule.self,
     GenericTypeNameRule.self,
+    HashFunctionRule.self,
     IdenticalOperandsRule.self,
     IdentifierNameRule.self,
     ImplicitGetterRule.self,

Source/SwiftLintFramework/Rules/Lint/HashFunctionRule.swift

@@ -0,0 +1,97 @@
+import Foundation
+import SourceKittenFramework
+
+public struct HashFunctionRule: ASTRule, ConfigurationProviderRule, AutomaticTestableRule {
+    public var configuration = SeverityConfiguration(.warning)
+
+    public init() {}
+
+    public static let description = RuleDescription(
+        identifier: "hash_function",
+        name: "Hash Function",
+        description: "Prefer using implementation `hash(into:)` instead of `hashValue`",
+        kind: .lint,
+        minSwiftVersion: .fourDotTwo,
+        nonTriggeringExamples: [
+            """
+            struct Foo: Hashable {
+                let bar: Int = 10
+
+                func hash(into hasher: inout Hasher) {
+                    hasher.combine(bar)
+                  }
+            }
+            """,
+            """
+            class Foo: Hashable {
+                let bar: Int = 10
+
+                func hash(into hasher: inout Hasher) {
+                    hasher.combine(bar)
+                  }
+            }
+            """,
+            """
+            var hashValue: Int { return 1 }
+            class Foo: Hashable { \n }
+            """,
+            """
+            class Foo: Hashable {
+                let bar: String = "Foo"
+
+                public var hashValue: String {
+                    return bar
+                }
+            }
+            """,
+            """
+            class Foo: Hashable {
+                let bar: String = "Foo"
+
+                public var hashValue: String {
+                    get { return bar }
+                    set { bar = newValue }
+                }
+            }
+            """
+        ],
+        triggeringExamples: [
+            """
+            struct Foo: Hashable {
+                let bar: Int = 10
+
+                public ↓var hashValue: Int {
+                    return bar
+                }
+            }
+            """,
+            """
+            class Foo: Hashable {
+                let bar: Int = 10
+
+                public ↓var hashValue: Int {
+                    return bar
+                }
+            }
+            """
+        ]
+    )
+
+    // MARK: - ASTRule
+
+    public func validate(file: File,
+                         kind: SwiftDeclarationKind,
+                         dictionary: [String: SourceKitRepresentable]) -> [StyleViolation] {
+        guard kind == .varInstance,
+            dictionary.setterAccessibility == nil,
+            dictionary.typeName == "Int",
+            dictionary.name == "hashValue",
+            let offset = dictionary.offset else {
+                return []
+        }
+
+        return [StyleViolation(ruleDescription: type(of: self).description,
+                               severity: configuration.severity,
+                               location: Location(file: file, byteOffset: offset))]
+    }
+}

SwiftLint.xcodeproj/project.pbxproj

@@ -138,9 +138,9 @@
 		78F032481D7D614300BE709A /* OverridenSuperCallConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = 78F032471D7D614300BE709A /* OverridenSuperCallConfiguration.swift */; };
 		7C0C2E7A1D2866CB0076435A /* ExplicitInitRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7C0C2E791D2866CB0076435A /* ExplicitInitRule.swift */; };
 		820F451E21073D7200AA056A /* ConditionalReturnsOnNewlineRuleTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 820F451D21073D7200AA056A /* ConditionalReturnsOnNewlineRuleTests.swift */; };
-		824AB64D2105C39F004B5A8F /* ConditionalReturnsOnNewlineConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = 824AB64C2105C39F004B5A8F /* ConditionalReturnsOnNewlineConfiguration.swift */; };
-		823EDC6221020D850070B7CD /* MultilineLiteralBracketsRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 823EDC6121020D850070B7CD /* MultilineLiteralBracketsRule.swift */; };
 		82144ACC20F640F200B06695 /* VerticalWhitespaceBetweenCasesRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82144ACB20F640F200B06695 /* VerticalWhitespaceBetweenCasesRule.swift */; };
+		823EDC6221020D850070B7CD /* MultilineLiteralBracketsRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 823EDC6121020D850070B7CD /* MultilineLiteralBracketsRule.swift */; };
+		824AB64D2105C39F004B5A8F /* ConditionalReturnsOnNewlineConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = 824AB64C2105C39F004B5A8F /* ConditionalReturnsOnNewlineConfiguration.swift */; };
 		825F19D11EEFF19700969EF1 /* ObjectLiteralRuleTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 825F19D01EEFF19700969EF1 /* ObjectLiteralRuleTests.swift */; };
 		827169B31F488181003FB9AF /* ExplicitEnumRawValueRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 827169B21F488181003FB9AF /* ExplicitEnumRawValueRule.swift */; };
 		827169B51F48D712003FB9AF /* NoGroupingExtensionRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 827169B41F48D712003FB9AF /* NoGroupingExtensionRule.swift */; };
@@ -200,6 +200,7 @@
 		C2B3C1612106F78C00088928 /* ConfigurationAliasesTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = C2B3C15F2106F78100088928 /* ConfigurationAliasesTests.swift */; };
 		C328A2F71E6759AE00A9E4D7 /* ExplicitTypeInterfaceRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = C328A2F51E67595500A9E4D7 /* ExplicitTypeInterfaceRule.swift */; };
 		C3DE5DAC1E7DF9CA00761483 /* FatalErrorMessageRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = C3DE5DAA1E7DF99B00761483 /* FatalErrorMessageRule.swift */; };
+		C3EF547821B5A4000009262F /* HashFunctionRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = C3EF547521B5A2190009262F /* HashFunctionRule.swift */; };
 		C946FECB1EAE67EE007DD778 /* LetVarWhitespaceRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = C946FEC91EAE5E20007DD778 /* LetVarWhitespaceRule.swift */; };
 		C9802F2F1E0C8AEE008AB27F /* TrailingCommaRuleTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = C9802F2E1E0C8AEE008AB27F /* TrailingCommaRuleTests.swift */; };
 		CC26ED07204DEB510013BBBC /* RuleIdentifier.swift in Sources */ = {isa = PBXBuildFile; fileRef = CC26ED05204DE86E0013BBBC /* RuleIdentifier.swift */; };
@@ -566,9 +567,9 @@
 		78F032471D7D614300BE709A /* OverridenSuperCallConfiguration.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = OverridenSuperCallConfiguration.swift; sourceTree = "<group>"; };
 		7C0C2E791D2866CB0076435A /* ExplicitInitRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ExplicitInitRule.swift; sourceTree = "<group>"; };
 		820F451D21073D7200AA056A /* ConditionalReturnsOnNewlineRuleTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ConditionalReturnsOnNewlineRuleTests.swift; sourceTree = "<group>"; };
-		824AB64C2105C39F004B5A8F /* ConditionalReturnsOnNewlineConfiguration.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ConditionalReturnsOnNewlineConfiguration.swift; sourceTree = "<group>"; };
-		823EDC6121020D850070B7CD /* MultilineLiteralBracketsRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MultilineLiteralBracketsRule.swift; sourceTree = "<group>"; };
 		82144ACB20F640F200B06695 /* VerticalWhitespaceBetweenCasesRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = VerticalWhitespaceBetweenCasesRule.swift; sourceTree = "<group>"; };
+		823EDC6121020D850070B7CD /* MultilineLiteralBracketsRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MultilineLiteralBracketsRule.swift; sourceTree = "<group>"; };
+		824AB64C2105C39F004B5A8F /* ConditionalReturnsOnNewlineConfiguration.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ConditionalReturnsOnNewlineConfiguration.swift; sourceTree = "<group>"; };
 		825F19D01EEFF19700969EF1 /* ObjectLiteralRuleTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ObjectLiteralRuleTests.swift; sourceTree = "<group>"; };
 		827169B21F488181003FB9AF /* ExplicitEnumRawValueRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ExplicitEnumRawValueRule.swift; sourceTree = "<group>"; };
 		827169B41F48D712003FB9AF /* NoGroupingExtensionRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = NoGroupingExtensionRule.swift; sourceTree = "<group>"; };
@@ -629,6 +630,7 @@
 		C2B3C15F2106F78100088928 /* ConfigurationAliasesTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ConfigurationAliasesTests.swift; sourceTree = "<group>"; };
 		C328A2F51E67595500A9E4D7 /* ExplicitTypeInterfaceRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ExplicitTypeInterfaceRule.swift; sourceTree = "<group>"; };
 		C3DE5DAA1E7DF99B00761483 /* FatalErrorMessageRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FatalErrorMessageRule.swift; sourceTree = "<group>"; };
+		C3EF547521B5A2190009262F /* HashFunctionRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = HashFunctionRule.swift; sourceTree = "<group>"; };
 		C946FEC91EAE5E20007DD778 /* LetVarWhitespaceRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = LetVarWhitespaceRule.swift; sourceTree = "<group>"; };
 		C9802F2E1E0C8AEE008AB27F /* TrailingCommaRuleTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = TrailingCommaRuleTests.swift; sourceTree = "<group>"; };
 		CC26ED05204DE86E0013BBBC /* RuleIdentifier.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RuleIdentifier.swift; sourceTree = "<group>"; };
@@ -997,6 +999,7 @@
 				E315B83B1DFA4BC500621B44 /* DynamicInlineRule.swift */,
 				62A3E95B209E078000547A86 /* EmptyXCTestMethodRule.swift */,
 				626B01B420A1735900D2C42F /* EmptyXCTestMethodRuleExamples.swift */,
+				C3EF547521B5A2190009262F /* HashFunctionRule.swift */,
 				D4E92D1E2137B4C9002EDD48 /* IdenticalOperandsRule.swift */,
 				D4441A27213279950020896F /* InertDeferRule.swift */,
 				C26330352073DAA200D7B4FD /* LowerACLThanParentRule.swift */,
@@ -1063,12 +1066,12 @@
 				D4EA77C91F81FACC00C315FB /* LiteralExpressionEndIdentationRule.swift */,
 				188B3FF1207D61040073C2D6 /* ModifierOrderRule.swift */,
 				BC8757392195CDD500CA7A74 /* ModifierOrderRuleExamples.swift */,
-                82F614F32106015100D23904 /* MultilineArgumentsBracketsRule.swift */,
+				82F614F32106015100D23904 /* MultilineArgumentsBracketsRule.swift */,
 				B25DCD071F7E9B5F0028A199 /* MultilineArgumentsRule.swift */,
 				B25DCD091F7E9BB50028A199 /* MultilineArgumentsRuleExamples.swift */,
 				3ABE19CD20B7CDE0009C2EC2 /* MultilineFunctionChainsRule.swift */,
-                823EDC6121020D850070B7CD /* MultilineLiteralBracketsRule.swift */,
-                82F614F12106014500D23904 /* MultilineParametersBracketsRule.swift */,
+				823EDC6121020D850070B7CD /* MultilineLiteralBracketsRule.swift */,
+				82F614F12106014500D23904 /* MultilineParametersBracketsRule.swift */,
 				6238AE411ED4D734006C3601 /* MultilineParametersRule.swift */,
 				621061BE1ED57E640082D51E /* MultilineParametersRuleExamples.swift */,
 				BB00B4E71F5216070079869F /* MultipleClosuresWithTrailingClosureRule.swift */,
@@ -1895,6 +1898,7 @@
 				006ECFC41C44E99E00EF6364 /* LegacyConstantRule.swift in Sources */,
 				82FE254120F604CB00295958 /* VerticalWhitespaceClosingBracesRule.swift in Sources */,
 				429644B61FB0A9B400D75128 /* SortedFirstLastRule.swift in Sources */,
+				C3EF547821B5A4000009262F /* HashFunctionRule.swift in Sources */,
 				31F1B6CC1F60BF4500A57456 /* SwitchCaseAlignmentRule.swift in Sources */,
 				E88DEA731B0984C400A66CB0 /* String+SwiftLint.swift in Sources */,
 				E88198591BEA95F100333A11 /* LeadingWhitespaceRule.swift in Sources */,

Tests/LinuxMain.swift

@@ -509,6 +509,12 @@ extension GlobTests {
     ]
 }
 
+extension HashFunctionRuleTests {
+    static var allTests: [(String, (HashFunctionRuleTests) -> () throws -> Void)] = [
+        ("testWithDefaultConfiguration", testWithDefaultConfiguration)
+    ]
+}
+
 extension IdenticalOperandsRuleTests {
     static var allTests: [(String, (IdenticalOperandsRuleTests) -> () throws -> Void)] = [
         ("testWithDefaultConfiguration", testWithDefaultConfiguration)
@@ -1406,6 +1412,7 @@ XCTMain([
     testCase(FunctionParameterCountRuleTests.allTests),
     testCase(GenericTypeNameRuleTests.allTests),
     testCase(GlobTests.allTests),
+    testCase(HashFunctionRuleTests.allTests),
     testCase(IdenticalOperandsRuleTests.allTests),
     testCase(IdentifierNameRuleTests.allTests),
     testCase(ImplicitGetterRuleTests.allTests),

Tests/SwiftLintFrameworkTests/AutomaticRuleTests.generated.swift

@@ -234,6 +234,12 @@ class FunctionDefaultParameterAtEndRuleTests: XCTestCase {
     }
 }
 
+class HashFunctionRuleTests: XCTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(HashFunctionRule.description)
+    }
+}
+
 class IdenticalOperandsRuleTests: XCTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(IdenticalOperandsRule.description)