Add unavailable_function opt-in rule

CHANGELOG.md

@@ -11,6 +11,12 @@
   [Marcelo Fabri](https://github.com/marcelofabri)
   [#898](https://github.com/realm/SwiftLint/issues/898)
 
+* Add `unavailable_function` opt-in rule to validate that functions that are
+  currently unimplemented (using a placeholder `fatalError`) are marked with
+  `@available(*, unavailable)`.  
+  [Marcelo Fabri](https://github.com/marcelofabri)
+  [#2127](https://github.com/realm/SwiftLint/issues/2127)
+
 #### Bug Fixes
 
 * None.

Rules.md

@@ -115,6 +115,7 @@
 * [Trailing Whitespace](#trailing-whitespace)
 * [Type Body Length](#type-body-length)
 * [Type Name](#type-name)
+* [Unavailable Function](#unavailable-function)
 * [Unneeded Break in Switch](#unneeded-break-in-switch)
 * [Unneeded Parentheses in Closure Argument](#unneeded-parentheses-in-closure-argument)
 * [Untyped Error in Catch](#untyped-error-in-catch)
@@ -17389,6 +17390,66 @@ protocol Foo {
 
 
 
+## Unavailable Function
+
+Identifier | Enabled by default | Supports autocorrection | Kind | Minimum Swift Compiler Version
+--- | --- | --- | --- | ---
+`unavailable_function` | Disabled | No | idiomatic | 4.1.0 
+
+Unimplemented functions should be marked as unavailable.
+
+### Examples
+
+<details>
+<summary>Non Triggering Examples</summary>
+
+```swift
+class ViewController: UIViewController {
+    @available(*, unavailable)
+    public required init?(coder aDecoder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+}
+```
+
+```swift
+func jsonValue(_ jsonString: String) -> NSObject {
+    let data = jsonString.data(using: .utf8)!
+    let result = try! JSONSerialization.jsonObject(with: data, options: [])
+    if let dict = (result as? [String: Any])?.bridge() {
+        return dict
+    } else if let array = (result as? [Any])?.bridge() {
+        return array
+    }
+    fatalError()
+}
+```
+
+</details>
+<details>
+<summary>Triggering Examples</summary>
+
+```swift
+class ViewController: UIViewController {
+    public required ↓init?(coder aDecoder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+}
+```
+
+```swift
+class ViewController: UIViewController {
+    public required ↓init?(coder aDecoder: NSCoder) {
+        let reason = "init(coder:) has not been implemented"
+        fatalError(reason)
+    }
+}
+```
+
+</details>
+
+
+
 ## Unneeded Break in Switch
 
 Identifier | Enabled by default | Supports autocorrection | Kind | Minimum Swift Compiler Version

Source/SwiftLintFramework/Models/MasterRuleList.swift

@@ -123,6 +123,7 @@ public let masterRuleList = RuleList(rules: [
     TrailingWhitespaceRule.self,
     TypeBodyLengthRule.self,
     TypeNameRule.self,
+    UnavailableFunctionRule.self,
     UnneededBreakInSwitchRule.self,
     UnneededParenthesesInClosureArgumentRule.self,
     UntypedErrorInCatchRule.self,

Source/SwiftLintFramework/Rules/UnavailableFunctionRule.swift

@@ -0,0 +1,100 @@
+//
+//  UnavailableFunctionRule.swift
+//  SwiftLint
+//
+//  Created by Marcelo Fabri on 04/09/18.
+//  Copyright © 2018 Realm. All rights reserved.
+//
+
+import Foundation
+import SourceKittenFramework
+
+public struct UnavailableFunctionRule: ASTRule, ConfigurationProviderRule, OptInRule {
+    public var configuration = SeverityConfiguration(.warning)
+
+    public init() {}
+
+    public static let description = RuleDescription(
+        identifier: "unavailable_function",
+        name: "Unavailable Function",
+        description: "Unimplemented functions should be marked as unavailable.",
+        kind: .idiomatic,
+        minSwiftVersion: .fourDotOne,
+        nonTriggeringExamples: [
+            """
+            class ViewController: UIViewController {
+                @available(*, unavailable)
+                public required init?(coder aDecoder: NSCoder) {
+                    fatalError("init(coder:) has not been implemented")
+                }
+            }
+            """,
+            """
+            func jsonValue(_ jsonString: String) -> NSObject {
+                let data = jsonString.data(using: .utf8)!
+                let result = try! JSONSerialization.jsonObject(with: data, options: [])
+                if let dict = (result as? [String: Any])?.bridge() {
+                    return dict
+                } else if let array = (result as? [Any])?.bridge() {
+                    return array
+                }
+                fatalError()
+            }
+            """
+        ],
+        triggeringExamples: [
+            """
+            class ViewController: UIViewController {
+                public required ↓init?(coder aDecoder: NSCoder) {
+                    fatalError("init(coder:) has not been implemented")
+                }
+            }
+            """,
+            """
+            class ViewController: UIViewController {
+                public required ↓init?(coder aDecoder: NSCoder) {
+                    let reason = "init(coder:) has not been implemented"
+                    fatalError(reason)
+                }
+            }
+            """
+        ]
+    )
+
+    public func validate(file: File, kind: SwiftDeclarationKind,
+                         dictionary: [String: SourceKitRepresentable]) -> [StyleViolation] {
+        guard SwiftDeclarationKind.functionKinds.contains(kind) else {
+            return []
+        }
+
+        let containsFatalError = dictionary.substructure.contains { dict -> Bool in
+            return dict.kind.flatMap(SwiftExpressionKind.init(rawValue:)) == .call && dict.name == "fatalError"
+        }
+
+        guard let offset = dictionary.offset, containsFatalError,
+            !isFunctionUnavailable(file: file, dictionary: dictionary),
+            let bodyOffset = dictionary.bodyOffset, let bodyLength = dictionary.bodyLength,
+            let range = file.contents.bridge().byteRangeToNSRange(start: bodyOffset, length: bodyLength),
+            file.match(pattern: "\\breturn\\b", with: [.keyword], range: range).isEmpty else {
+                return []
+        }
+
+        return [
+            StyleViolation(ruleDescription: type(of: self).description,
+                           severity: configuration.severity,
+                           location: Location(file: file, byteOffset: offset))
+        ]
+    }
+
+    private func isFunctionUnavailable(file: File, dictionary: [String: SourceKitRepresentable]) -> Bool {
+        return dictionary.swiftAttributes.contains { dict -> Bool in
+            guard dict.attribute.flatMap(SwiftDeclarationAttributeKind.init(rawValue:)) == .available,
+                let offset = dict.offset, let length = dict.length,
+                let contents = file.contents.bridge().substringWithByteRange(start: offset, length: length) else {
+                    return false
+            }
+
+            return contents.contains("unavailable")
+        }
+    }
+}

SwiftLint.xcodeproj/project.pbxproj

@@ -240,6 +240,7 @@
 		D4DABFD91E2C59BC009617B6 /* NotificationCenterDetachmentRuleExamples.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4DABFD81E2C59BC009617B6 /* NotificationCenterDetachmentRuleExamples.swift */; };
 		D4DAE8BC1DE14E8F00B0AE7A /* NimbleOperatorRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4DAE8BB1DE14E8F00B0AE7A /* NimbleOperatorRule.swift */; };
 		D4DB92251E628898005DE9C1 /* TodoRuleTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4DB92241E628898005DE9C1 /* TodoRuleTests.swift */; };
+		D4DE9133207B4750000FFAA8 /* UnavailableFunctionRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4DE9131207B4731000FFAA8 /* UnavailableFunctionRule.swift */; };
 		D4E2BA851F6CD77B00E8E184 /* ArrayInitRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4E2BA841F6CD77B00E8E184 /* ArrayInitRule.swift */; };
 		D4EA77C81F817FD200C315FB /* UnneededBreakInSwitchRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4EA77C71F817FD200C315FB /* UnneededBreakInSwitchRule.swift */; };
 		D4EA77CA1F81FACC00C315FB /* LiteralExpressionEndIdentationRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4EA77C91F81FACC00C315FB /* LiteralExpressionEndIdentationRule.swift */; };
@@ -622,6 +623,7 @@
 		D4DABFD81E2C59BC009617B6 /* NotificationCenterDetachmentRuleExamples.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = NotificationCenterDetachmentRuleExamples.swift; sourceTree = "<group>"; };
 		D4DAE8BB1DE14E8F00B0AE7A /* NimbleOperatorRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = NimbleOperatorRule.swift; sourceTree = "<group>"; };
 		D4DB92241E628898005DE9C1 /* TodoRuleTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = TodoRuleTests.swift; sourceTree = "<group>"; };
+		D4DE9131207B4731000FFAA8 /* UnavailableFunctionRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UnavailableFunctionRule.swift; sourceTree = "<group>"; };
 		D4E2BA841F6CD77B00E8E184 /* ArrayInitRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ArrayInitRule.swift; sourceTree = "<group>"; };
 		D4EA77C71F817FD200C315FB /* UnneededBreakInSwitchRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UnneededBreakInSwitchRule.swift; sourceTree = "<group>"; };
 		D4EA77C91F81FACC00C315FB /* LiteralExpressionEndIdentationRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LiteralExpressionEndIdentationRule.swift; sourceTree = "<group>"; };
@@ -1179,6 +1181,7 @@
 				E88DEA8D1B0999CD00A66CB0 /* TypeBodyLengthRule.swift */,
 				E88DEA911B099B1F00A66CB0 /* TypeNameRule.swift */,
 				D4130D981E16CC1300242361 /* TypeNameRuleExamples.swift */,
+				D4DE9131207B4731000FFAA8 /* UnavailableFunctionRule.swift */,
 				D4EA77C71F817FD200C315FB /* UnneededBreakInSwitchRule.swift */,
 				D46A317E1F1CEDCD00AF914A /* UnneededParenthesesInClosureArgumentRule.swift */,
 				181D9E162038343D001F6887 /* UntypedErrorInCatchRule.swift */,
@@ -1648,6 +1651,7 @@
 				3BCC04D21C4F56D3006073C3 /* NameConfiguration.swift in Sources */,
 				D4C27BFE1E12D53F00DF713E /* Version.swift in Sources */,
 				B2902A0E1D6681F700BFCCF7 /* PrivateUnitTestConfiguration.swift in Sources */,
+				D4DE9133207B4750000FFAA8 /* UnavailableFunctionRule.swift in Sources */,
 				D47A510E1DB29EEB00A4CC21 /* SwitchCaseOnNewlineRule.swift in Sources */,
 				D462021F1E15F52D0027AAD1 /* NumberSeparatorRuleExamples.swift in Sources */,
 				D4DA1DF41E17511D0037413D /* CompilerProtocolInitRule.swift in Sources */,

Tests/LinuxMain.swift

@@ -513,6 +513,7 @@ extension RulesTests {
         ("testTrailingSemicolon", testTrailingSemicolon),
         ("testTrailingWhitespace", testTrailingWhitespace),
         ("testTypeBodyLength", testTypeBodyLength),
+        ("testUnavailableFunction", testUnavailableFunction),
         ("testUnneededBreakInSwitch", testUnneededBreakInSwitch),
         ("testUnneededParenthesesInClosureArgument", testUnneededParenthesesInClosureArgument),
         ("testUntypedErrorInCatch", testUntypedErrorInCatch),

Tests/SwiftLintFrameworkTests/RulesTests.swift

@@ -433,6 +433,10 @@ class RulesTests: XCTestCase {
         verifyRule(TypeBodyLengthRule.description)
     }
 
+    func testUnavailableFunction() {
+        verifyRule(UnavailableFunctionRule.description)
+    }
+
     func testUnneededBreakInSwitch() {
         verifyRule(UnneededBreakInSwitchRule.description)
     }