Adding Legacy ObjC Type Rule #2758

CHANGELOG.md

@@ -49,6 +49,11 @@
 * Make `strong_iboutlet` rule correctable.  
   [MaxHaertwig](https://github.com/maxhaertwig)
 
+* Add `legacy_objc_type` opt-in rule to warn against using
+  bridged Objective-C reference types instead of Swift value types.  
+  [Blake](https://github.com/72A12F4E)
+  [#2758](https://github.com/realm/SwiftLint/issues/2758)
+
 #### Bug Fixes
 
 * Fix typos in configuration options for `file_name` rule.  

Source/SwiftLintFramework/Models/PrimaryRuleList.swift

@@ -91,6 +91,7 @@ public let primaryRuleList = RuleList(rules: [
     LegacyHashingRule.self,
     LegacyMultipleRule.self,
     LegacyNSGeometryFunctionsRule.self,
+    LegacyObjcTypeRule.self,
     LegacyRandomRule.self,
     LetVarWhitespaceRule.self,
     LineLengthRule.self,

Source/SwiftLintFramework/Rules/Idiomatic/LegacyObjcTypeRule.swift

@@ -0,0 +1,63 @@
+import Foundation
+import SourceKittenFramework
+
+private let legacyObjcTypes = [
+    "NSAffineTransform",
+    "NSArray",
+    "NSCalendar",
+    "NSCharacterSet",
+    "NSData",
+    "NSDateComponents",
+    "NSDateInterval",
+    "NSDate",
+    "NSDecimalNumber",
+    "NSDictionary",
+    "NSIndexPath",
+    "NSIndexSet",
+    "NSLocale",
+    "NSMeasurement",
+    "NSNotification",
+    "NSNumber",
+    "NSPersonNameComponents",
+    "NSSet",
+    "NSString",
+    "NSTimeZone",
+    "NSURL",
+    "NSURLComponents",
+    "NSURLQueryItem",
+    "NSURLRequest",
+    "NSUUID"
+]
+
+public struct LegacyObjcTypeRule: OptInRule, ConfigurationProviderRule, AutomaticTestableRule {
+    public var configuration = SeverityConfiguration(.warning)
+
+    public init() {}
+
+    public static let description = RuleDescription(
+        identifier: "legacy_objc_type",
+        name: "Legacy Objective-C Reference Type",
+        description: "Prefer Swift value types to bridged Objective-C reference types",
+        kind: .idiomatic,
+        nonTriggeringExamples: [
+            Example("var array = Array<Int>()\n"),
+            Example("var calendar: Calendar? = nil")
+        ],
+        triggeringExamples: [
+            Example("var array = NSArray()"),
+            Example("var calendar: NSCalendar? = nil")
+        ]
+    )
+
+    private let pattern = legacyObjcTypes.joined(separator: "|")
+
+    public func validate(file: SwiftLintFile) -> [StyleViolation] {
+        return file.match(pattern: pattern)
+            .filter { !Set($0.1).isDisjoint(with: [.typeidentifier, .identifier]) }
+            .map {
+                StyleViolation(ruleDescription: Self.description,
+                               severity: configuration.severity,
+                               location: Location(file: file, characterOffset: $0.0.location))
+            }
+    }
+}

Tests/LinuxMain.swift

@@ -858,6 +858,12 @@ extension LegacyNSGeometryFunctionsRuleTests {
     ]
 }
 
+extension LegacyObjcTypeRuleTests {
+    static var allTests: [(String, (LegacyObjcTypeRuleTests) -> () throws -> Void)] = [
+        ("testWithDefaultConfiguration", testWithDefaultConfiguration)
+    ]
+}
+
 extension LegacyRandomRuleTests {
     static var allTests: [(String, (LegacyRandomRuleTests) -> () throws -> Void)] = [
         ("testWithDefaultConfiguration", testWithDefaultConfiguration)
@@ -1878,6 +1884,7 @@ XCTMain([
     testCase(LegacyHashingRuleTests.allTests),
     testCase(LegacyMultipleRuleTests.allTests),
     testCase(LegacyNSGeometryFunctionsRuleTests.allTests),
+    testCase(LegacyObjcTypeRuleTests.allTests),
     testCase(LegacyRandomRuleTests.allTests),
     testCase(LetVarWhitespaceRuleTests.allTests),
     testCase(LineEndingTests.allTests),

Tests/SwiftLintFrameworkTests/AutomaticRuleTests.generated.swift

@@ -360,6 +360,12 @@ class LegacyNSGeometryFunctionsRuleTests: XCTestCase {
     }
 }
 
+class LegacyObjcTypeRuleTests: XCTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(LegacyObjcTypeRule.description)
+    }
+}
+
 class LegacyRandomRuleTests: XCTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(LegacyRandomRule.description)