Introduction of Yoda condition checking.

This PR aims to implement [realm#1924][1].
[1]: realm#1924

CHANGELOG.md

@@ -9,6 +9,10 @@
 * Invalidate cache when Swift patch version changes.  
   [Norio Nomura](https://github.com/norio-nomura)
 
+* Add `yoda_condition` opt-in rule which warns to avoid Yoda conditions.  
+  [Daniel Metzing](https://github.com/dirtydanee)
+  [#1924](https://github.com/realm/SwiftLint/issues/1924)
+
 ##### Bug Fixes
 
 * None.
@@ -106,7 +110,10 @@
 
 ##### Enhancements
 
-* None.
+* Add `private_action` opt-in rule which warns agaist public
+  @IBAction methods.  
+  [Ornithologist Coder](https://github.com/ornithocoder)
+  [#1931](https://github.com/realm/SwiftLint/issues/1931)
 
 ##### Bug Fixes
 

Rules.md

@@ -73,6 +73,7 @@
 * [Overridden methods call super](#overridden-methods-call-super)
 * [Override in Extension](#override-in-extension)
 * [Pattern Matching Keywords](#pattern-matching-keywords)
+* [Private Actions](#private-actions)
 * [Private Outlets](#private-outlets)
 * [Private over fileprivate](#private-over-fileprivate)
 * [Private Unit Test](#private-unit-test)
@@ -117,6 +118,7 @@
 * [Void Return](#void-return)
 * [Weak Delegate](#weak-delegate)
 * [XCTFail Message](#xctfail-message)
+* [Yoda condition rule](#yoda-condition-rule)
 --------
 
 ## Array Init
@@ -8790,6 +8792,146 @@ switch foo {
 
 
 
+## Private Actions
+
+Identifier | Enabled by default | Supports autocorrection | Kind 
+--- | --- | --- | ---
+`private_action` | Disabled | No | lint
+
+IBActions should be private.
+
+### Examples
+
+<details>
+<summary>Non Triggering Examples</summary>
+
+```swift
+class Foo {
+	@IBAction private func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+struct Foo {
+	@IBAction private func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+class Foo {
+	@IBAction fileprivate func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+struct Foo {
+	@IBAction fileprivate func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+private extension Foo {
+	@IBAction func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+fileprivate extension Foo {
+	@IBAction func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+</details>
+<details>
+<summary>Triggering Examples</summary>
+
+```swift
+class Foo {
+	@IBAction ↓func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+struct Foo {
+	@IBAction ↓func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+class Foo {
+	@IBAction public ↓func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+struct Foo {
+	@IBAction public ↓func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+class Foo {
+	@IBAction internal ↓func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+struct Foo {
+	@IBAction internal ↓func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+extension Foo {
+	@IBAction ↓func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+extension Foo {
+	@IBAction public ↓func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+extension Foo {
+	@IBAction internal ↓func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+public extension Foo {
+	@IBAction ↓func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+```swift
+internal extension Foo {
+	@IBAction ↓func barButtonTapped(_ sender: UIButton) {}
+}
+
+```
+
+</details>
+
+
+
 ## Private Outlets
 
 Identifier | Enabled by default | Supports autocorrection | Kind 
@@ -16145,3 +16287,80 @@ func testFoo() {
 ```
 
 </details>
+
+
+
+## Yoda condition rule
+
+Identifier | Enabled by default | Supports autocorrection | Kind 
+--- | --- | --- | ---
+`yoda_condition` | Disabled | No | lint
+
+The variable should be placed on the left, the constant on the right of a comparison operator.
+
+### Examples
+
+<details>
+<summary>Non Triggering Examples</summary>
+
+```swift
+if foo == 42 {}
+
+```
+
+```swift
+if foo <= 42.42 {}
+
+```
+
+```swift
+guard foo >= 42 else { return }
+
+```
+
+```swift
+guard foo != "str str" else { return }
+```
+
+```swift
+while foo < 10 { }
+
+```
+
+```swift
+while foo > 1 { }
+
+```
+
+</details>
+<details>
+<summary>Triggering Examples</summary>
+
+```swift
+↓if 42 == foo {}
+
+```
+
+```swift
+↓if 42.42 >= foo {}
+
+```
+
+```swift
+↓guard 42 <= foo else { return }
+
+```
+
+```swift
+↓guard "str str" != foo else { return }
+```
+
+```swift
+↓while 10 > foo { }
+```
+
+```swift
+↓while 1 < foo { }
+```
+
+</details>

Source/SwiftLintFramework/Models/MasterRuleList.swift

@@ -81,6 +81,7 @@ public let masterRuleList = RuleList(rules: [
     OverriddenSuperCallRule.self,
     OverrideInExtensionRule.self,
     PatternMatchingKeywordsRule.self,
+    PrivateActionRule.self,
     PrivateOutletRule.self,
     PrivateOverFilePrivateRule.self,
     PrivateUnitTestRule.self,
@@ -124,5 +125,6 @@ public let masterRuleList = RuleList(rules: [
     VerticalWhitespaceRule.self,
     VoidReturnRule.self,
     WeakDelegateRule.self,
-    XCTFailMessageRule.self
+    XCTFailMessageRule.self,
+    YodaConditionRule.self
 ])

Source/SwiftLintFramework/Rules/PrivateActionRule.swift

@@ -0,0 +1,64 @@
+//
+//  PrivateActionRule.swift
+//  SwiftLint
+//
+//  Created by Ornithologist Coder on 11/7/17.
+//  Copyright © 2016 Realm. All rights reserved.
+//
+
+import Foundation
+import SourceKittenFramework
+
+public struct PrivateActionRule: ASTRule, OptInRule, ConfigurationProviderRule {
+    public var configuration = SeverityConfiguration(.warning)
+
+    public init() {}
+
+    public static let description = RuleDescription(
+        identifier: "private_action",
+        name: "Private Actions",
+        description: "IBActions should be private.",
+        kind: .lint,
+        nonTriggeringExamples: [
+            "class Foo {\n\t@IBAction private func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "struct Foo {\n\t@IBAction private func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "class Foo {\n\t@IBAction fileprivate func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "struct Foo {\n\t@IBAction fileprivate func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "private extension Foo {\n\t@IBAction func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "fileprivate extension Foo {\n\t@IBAction func barButtonTapped(_ sender: UIButton) {}\n}\n"
+        ],
+        triggeringExamples: [
+            "class Foo {\n\t@IBAction ↓func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "struct Foo {\n\t@IBAction ↓func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "class Foo {\n\t@IBAction public ↓func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "struct Foo {\n\t@IBAction public ↓func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "class Foo {\n\t@IBAction internal ↓func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "struct Foo {\n\t@IBAction internal ↓func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "extension Foo {\n\t@IBAction ↓func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "extension Foo {\n\t@IBAction public ↓func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "extension Foo {\n\t@IBAction internal ↓func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "public extension Foo {\n\t@IBAction ↓func barButtonTapped(_ sender: UIButton) {}\n}\n",
+            "internal extension Foo {\n\t@IBAction ↓func barButtonTapped(_ sender: UIButton) {}\n}\n"
+        ]
+    )
+
+    public func validate(file: File,
+                         kind: SwiftDeclarationKind,
+                         dictionary: [String: SourceKitRepresentable]) -> [StyleViolation] {
+        guard
+            let offset = dictionary.offset,
+            kind == .functionMethodInstance,
+            dictionary.enclosedSwiftAttributes.contains("source.decl.attribute.ibaction"),
+            let controlLevel = dictionary.accessibility.flatMap(AccessControlLevel.init(identifier:)),
+            controlLevel.isPrivate == false
+            else {
+                return []
+        }
+
+        return [
+            StyleViolation(ruleDescription: type(of: self).description,
+                           severity: configuration.severity,
+                           location: Location(file: file, byteOffset: offset))
+        ]
+    }
+}

Source/SwiftLintFramework/Rules/RuleConfigurations/YodaConditionConfiguration.swift

@@ -0,0 +1,31 @@
+//
+//  YodaConditionConfiguration.swift
+//  SwiftLint
+//
+//  Created by Daniel.Metzing on 02/12/17.
+//  Copyright © 2017 Realm. All rights reserved.
+//
+
+public struct YodaConditionConfiguration: RuleConfiguration, Equatable {
+
+    private(set) var severityConfiguration = SeverityConfiguration(.warning)
+
+    public var consoleDescription: String {
+        return severityConfiguration.consoleDescription
+    }
+
+    public mutating func apply(configuration: Any) throws {
+        guard let configuration = configuration as? [String: Any] else {
+            throw ConfigurationError.unknownConfiguration
+        }
+
+        if let severityString = configuration["severity"] as? String {
+            try severityConfiguration.apply(configuration: severityString)
+        }
+    }
+
+    public static func == (lhs: YodaConditionConfiguration,
+                           rhs: YodaConditionConfiguration) -> Bool {
+        return lhs.severityConfiguration == rhs.severityConfiguration
+    }
+}