From 5d6c2ec3e797cc159161e7d4b9ca2feaa22e683f Mon Sep 17 00:00:00 2001
From: Marcelo Fabri <marcelofabrimf@gmail.com>
Date: Fri, 6 Jan 2017 02:23:19 -0200
Subject: [PATCH] Add shorthand_operator rule

Fixes #902
---
 CHANGELOG.md                                  |   5 +
 .../Models/MasterRuleList.swift               |   1 +
 .../Rules/ShorthandOperatorRule.swift         | 102 ++++++++++++++++++
 SwiftLint.xcodeproj/project.pbxproj           |   4 +
 .../SwiftLintFrameworkTests/RulesTests.swift  |   5 +
 5 files changed, 117 insertions(+)
 create mode 100644 Source/SwiftLintFramework/Rules/ShorthandOperatorRule.swift

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6782dfb97..e7c00fee6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -103,6 +103,11 @@
   [Javier Hernández](https://github.com/jaherhi)
   [#384](https://github.com/realm/SwiftLint/issues/384)
 
+* Add `shorthand_operator` rule that validates that shorthand operators should
+  be used when possible.  
+  [Marcelo Fabri](https://github.com/marcelofabri)
+  [#902](https://github.com/realm/SwiftLint/issues/902)
+
 ##### Bug Fixes
 
 * Ignore close parentheses on `vertical_parameter_alignment` rule.  
diff --git a/Source/SwiftLintFramework/Models/MasterRuleList.swift b/Source/SwiftLintFramework/Models/MasterRuleList.swift
index 90558cca5..f39d2cbc7 100644
--- a/Source/SwiftLintFramework/Models/MasterRuleList.swift
+++ b/Source/SwiftLintFramework/Models/MasterRuleList.swift
@@ -122,6 +122,7 @@ public let masterRuleList = RuleList(rules:
     RedundantStringEnumValueRule.self,
     RedundantVoidReturnRule.self,
     ReturnArrowWhitespaceRule.self,
+    ShorthandOperatorRule.self,
     SortedImportsRule.self,
     StatementPositionRule.self,
     SwitchCaseOnNewlineRule.self,
diff --git a/Source/SwiftLintFramework/Rules/ShorthandOperatorRule.swift b/Source/SwiftLintFramework/Rules/ShorthandOperatorRule.swift
new file mode 100644
index 000000000..af9d1d4b9
--- /dev/null
+++ b/Source/SwiftLintFramework/Rules/ShorthandOperatorRule.swift
@@ -0,0 +1,102 @@
+//
+//  ShorthandOperatorRule.swift
+//  SwiftLint
+//
+//  Created by Marcelo Fabri on 01/06/17.
+//  Copyright © 2017 Realm. All rights reserved.
+//
+
+import SourceKittenFramework
+
+public struct ShorthandOperatorRule: ConfigurationProviderRule {
+
+    public var configuration = SeverityConfiguration(.error)
+
+    public init() {}
+
+    public static let description = RuleDescription(
+        identifier: "shorthand_operator",
+        name: "Shorthand Operator",
+        description: "Prefer shorhand operators (+=, -=, *=, /=) over doing the operation and assigning.",
+        nonTriggeringExamples: allOperators.flatMap { operation in
+            [
+                "foo \(operation)= 1",
+                "foo \(operation)= variable",
+                "foo \(operation)= bar.method()"
+            ]
+        },
+        triggeringExamples: allOperators.flatMap { operation in
+            [
+                "↓foo = foo \(operation) 1\n",
+                "↓foo = foo \(operation) aVariable\n",
+                "↓foo = foo \(operation) bar.method()\n",
+                "↓foo = 1 \(operation) foo\n",
+                "↓foo = aVariable \(operation) foo\n",
+                "↓foo = bar.method() \(operation) foo\n",
+                "↓foo = bar.method(param: 1, otherParam: 2) \(operation) foo\n"
+            ]
+        }
+    )
+
+    private static let allOperators = ["+", "-", "/", "*"]
+
+    private static let pattern: String = {
+        let escapedOperators = allOperators.map { "\\\($0)" }.joined()
+        let operators = "[\(escapedOperators)]"
+        let operand = "[\\w\\d\\.]+?"
+        let spaces = "[^\\S\\r\\n]*?"
+        let otherOperand = "\(spaces).+?\(spaces)"
+
+        let pattern1 = "\\b(\(operand))\(spaces)=\(spaces)(\\1)\(spaces)\(operators)"
+        let pattern2 = "\\b(\(operand))\(spaces)=\(otherOperand)\(operators)\(spaces)(\\3)"
+
+        return "\(pattern1)|\(pattern2)"
+    }()
+
+    // swiftlint:disable:next force_try
+    private static let regex = try! NSRegularExpression(pattern: pattern, options: [])
+
+    public func validateFile(_ file: File) -> [StyleViolation] {
+        let contents = file.contents.bridge()
+        let range = NSRange(location: 0, length: contents.length)
+
+        let matches = ShorthandOperatorRule.regex.matches(in: file.contents, options: [], range: range)
+        return matches.flatMap { match -> StyleViolation? in
+
+            // byteRanges will have the ranges of captured groups
+            let byteRanges: [NSRange?] = (1..<match.numberOfRanges).map { rangeIdx in
+                let range = match.rangeAt(rangeIdx)
+                guard range.location != NSNotFound else {
+                    return nil
+                }
+
+                return contents.NSRangeToByteRange(start: range.location, length: range.length)
+            }
+
+            guard byteRanges[0] != nil || byteRanges[2] != nil else {
+                return nil
+            }
+
+            let kindsInCaptureGroups = byteRanges.map { range in
+                range.flatMap { file.syntaxMap.tokensIn($0).flatMap { SyntaxKind(rawValue: $0.type) } } ?? []
+            }
+
+            let groupIndexes: [Int]
+            if byteRanges[0] != nil {
+                // it's a match from pattern1
+                groupIndexes = [0, 1]
+            } else {
+                // it's a match from pattern2
+                groupIndexes = [2, 3]
+            }
+
+            for idx in groupIndexes where kindsInCaptureGroups[idx] != [.identifier] {
+                return nil
+            }
+
+            return StyleViolation(ruleDescription: type(of: self).description,
+                                  severity: configuration.severity,
+                                  location: Location(file: file, characterOffset: match.range.location))
+        }
+    }
+}
diff --git a/SwiftLint.xcodeproj/project.pbxproj b/SwiftLint.xcodeproj/project.pbxproj
index 0944dc0aa..fd948b1c7 100644
--- a/SwiftLint.xcodeproj/project.pbxproj
+++ b/SwiftLint.xcodeproj/project.pbxproj
@@ -129,6 +129,7 @@
 		D4C4A34C1DEA4FF000E0E04C /* AttributesConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4C4A34A1DEA4FD700E0E04C /* AttributesConfiguration.swift */; };
 		D4C4A34E1DEA877200E0E04C /* FileHeaderRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4C4A34D1DEA877200E0E04C /* FileHeaderRule.swift */; };
 		D4C4A3521DEFBBB700E0E04C /* FileHeaderConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4C4A3511DEFBBB700E0E04C /* FileHeaderConfiguration.swift */; };
+		D4D5A5FF1E1F3A1C00D15E0C /* ShorthandOperatorRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4D5A5FE1E1F3A1C00D15E0C /* ShorthandOperatorRule.swift */; };
 		D4DA1DF41E17511D0037413D /* CompilerProtocolInitRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4DA1DF31E17511D0037413D /* CompilerProtocolInitRule.swift */; };
 		D4DA1DFA1E18D6200037413D /* LargeTupleRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4DA1DF91E18D6200037413D /* LargeTupleRule.swift */; };
 		D4DA1DFE1E1A10DB0037413D /* NumberSeparatorConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4DA1DFD1E1A10DB0037413D /* NumberSeparatorConfiguration.swift */; };
@@ -389,6 +390,7 @@
 		D4C4A34A1DEA4FD700E0E04C /* AttributesConfiguration.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = AttributesConfiguration.swift; sourceTree = "<group>"; };
 		D4C4A34D1DEA877200E0E04C /* FileHeaderRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FileHeaderRule.swift; sourceTree = "<group>"; };
 		D4C4A3511DEFBBB700E0E04C /* FileHeaderConfiguration.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FileHeaderConfiguration.swift; sourceTree = "<group>"; };
+		D4D5A5FE1E1F3A1C00D15E0C /* ShorthandOperatorRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ShorthandOperatorRule.swift; sourceTree = "<group>"; };
 		D4DA1DF31E17511D0037413D /* CompilerProtocolInitRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = CompilerProtocolInitRule.swift; sourceTree = "<group>"; };
 		D4DA1DF91E18D6200037413D /* LargeTupleRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = LargeTupleRule.swift; sourceTree = "<group>"; };
 		D4DA1DFD1E1A10DB0037413D /* NumberSeparatorConfiguration.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = NumberSeparatorConfiguration.swift; sourceTree = "<group>"; };
@@ -820,6 +822,7 @@
 				D4B022B11E10B613007E5297 /* RedundantVoidReturnRule.swift */,
 				E57B23C01B1D8BF000DEA512 /* ReturnArrowWhitespaceRule.swift */,
 				3BCC04CE1C4F56D3006073C3 /* RuleConfigurations */,
+				D4D5A5FE1E1F3A1C00D15E0C /* ShorthandOperatorRule.swift */,
 				D286EC001E02DA190003CF72 /* SortedImportsRule.swift */,
 				692B60AB1BD8F2E700C7AA22 /* StatementPositionRule.swift */,
 				D47A510D1DB29EEB00A4CC21 /* SwitchCaseOnNewlineRule.swift */,
@@ -1238,6 +1241,7 @@
 				E832F10B1B17E2F5003F265F /* NSFileManager+SwiftLint.swift in Sources */,
 				E816194C1BFBF35D00946723 /* SwiftDeclarationKind+SwiftLint.swift in Sources */,
 				3BA79C9B1C4767910057E705 /* NSRange+SwiftLint.swift in Sources */,
+				D4D5A5FF1E1F3A1C00D15E0C /* ShorthandOperatorRule.swift in Sources */,
 				4DCB8E7F1CBE494E0070FCF0 /* RegexHelpers.swift in Sources */,
 				E86396C21BADAAE5002C9E88 /* Reporter.swift in Sources */,
 				D4B0228E1E0CC608007E5297 /* ClassDelegateProtocolRule.swift in Sources */,
diff --git a/Tests/SwiftLintFrameworkTests/RulesTests.swift b/Tests/SwiftLintFrameworkTests/RulesTests.swift
index 7b8c39ce8..4c5b9a6c5 100644
--- a/Tests/SwiftLintFrameworkTests/RulesTests.swift
+++ b/Tests/SwiftLintFrameworkTests/RulesTests.swift
@@ -217,6 +217,10 @@ class RulesTests: XCTestCase {
         verifyRule(ReturnArrowWhitespaceRule.description)
     }
 
+    func testShorthandOperator() {
+        verifyRule(ShorthandOperatorRule.description)
+    }
+
     func testSortedImports() {
         verifyRule(SortedImportsRule.description)
     }
@@ -381,6 +385,7 @@ extension RulesTests {
             ("testRedundantStringEnumValue", testRedundantStringEnumValue),
             ("testRedundantVoidReturn", testRedundantVoidReturn),
             ("testReturnArrowWhitespace", testReturnArrowWhitespace),
+            ("testShorthandOperator", testShorthandOperator),
             ("testSortedImports", testSortedImports),
             ("testStatementPosition", testStatementPosition),
             ("testStatementPositionUncuddled", testStatementPositionUncuddled),