Rewrite ExplicitInitRule as ASTRule

CHANGELOG.md

@@ -35,6 +35,11 @@
   [Marcelo Fabri](https://github.com/marcelofabri)
   [#681](https://github.com/realm/SwiftLint/issues/681)
 
+* Add ``ExplicitInitRule`` Opt-In rule to discourage calling ``init``
+  directly.  
+  [Matt Taube](https://github.com/mtaube)
+  [#715](https://github.com/realm/SwiftLint/pull/715)
+
 ##### Bug Fixes
 
 * Fixed whitespace being added to TODO messages.  

Source/SwiftLintFramework/Models/MasterRuleList.swift

@@ -50,6 +50,7 @@ public let masterRuleList = RuleList(rules:
     CustomRules.self,
     CyclomaticComplexityRule.self,
     EmptyCountRule.self,
+    ExplicitInitRule.self,
     FileLengthRule.self,
     ForceCastRule.self,
     ForceTryRule.self,

Source/SwiftLintFramework/Rules/ExplicitInitRule.swift

@@ -0,0 +1,124 @@
+//
+//  ExplicitInitRule.swift
+//  SwiftLint
+//
+//  Created by Matt Taube on 7/2/16.
+//  Copyright (c) 2016 Realm. All rights reserved.
+//
+
+import Foundation
+import SourceKittenFramework
+
+public struct ExplicitInitRule: ASTRule, ConfigurationProviderRule, CorrectableRule, OptInRule {
+
+    public var configuration = SeverityConfiguration(.Warning)
+
+    public init() {}
+
+    public static let description = RuleDescription(
+        identifier: "explicit_init",
+        name: "Explicit Init",
+        description: "Explicitly calling .init() should be avoided.",
+        nonTriggeringExamples: [
+            "import Foundation; class C: NSObject { override init() { super.init() }}", // super
+            "struct S { let n: Int }; extension S { init() { self.init(n: 1) } }",      // self
+            "[1].flatMap(String.init)",                   // pass init as closure
+            "[String.self].map { $0.init(1) }",           // initialize from a metatype value
+            "[String.self].map { type in type.init(1) }", // initialize from a metatype value
+        ],
+        triggeringExamples: [
+            "[1].flatMap{String↓.init($0)}",
+            "[String.self].map { Type in Type↓.init(1) }", // starting with capital assumes as type
+        ],
+        corrections: [
+            "[1].flatMap{String.init($0)}" : "[1].flatMap{String($0)}",
+        ]
+    )
+
+    public enum Kind: String {
+        case expr_call = "source.lang.swift.expr.call"
+        case other
+        public init?(rawValue: String) {
+            switch rawValue {
+            case expr_call.rawValue: self = .expr_call
+            default: self = .other
+            }
+        }
+    }
+
+    public func validateFile(
+        file: File,
+        kind: ExplicitInitRule.Kind,
+        dictionary: [String: SourceKitRepresentable]) -> [StyleViolation] {
+        return violationRangesInFile(file, kind: kind, dictionary: dictionary).map {
+            StyleViolation(ruleDescription: self.dynamicType.description,
+                severity: configuration.severity,
+                location: Location(file: file, characterOffset: $0.location))
+        }
+    }
+
+    private let initializerWithType = regex("^[A-Z].*\\.init$")
+
+    private func violationRangesInFile(
+        file: File,
+        kind: ExplicitInitRule.Kind,
+        dictionary: [String: SourceKitRepresentable]) -> [NSRange] {
+
+        func isExpected(name: String) -> Bool {
+            let range = NSRange(location: 0, length: name.utf16.count)
+            return !["super.init", "self.init"].contains(name)
+                && initializerWithType.numberOfMatchesInString(name, options: [], range: range) != 0
+        }
+
+        let length = ".init".utf8.count
+
+        guard kind == .expr_call,
+            let name = dictionary["key.name"] as? String where isExpected(name),
+            let nameOffset = dictionary["key.nameoffset"] as? Int64,
+            let nameLength = dictionary["key.namelength"] as? Int64,
+            let range = (file.contents as NSString)
+                .byteRangeToNSRange(start: Int(nameOffset + nameLength) - length, length: length)
+            else { return [] }
+        return [range]
+    }
+
+    private func violationRangesInFile(
+        file: File,
+        dictionary: [String: SourceKitRepresentable]) -> [NSRange] {
+        let substructure = dictionary["key.substructure"] as? [SourceKitRepresentable] ?? []
+        return substructure.flatMap { subItem -> [NSRange] in
+            guard let subDict = subItem as? [String: SourceKitRepresentable],
+                kindString = subDict["key.kind"] as? String,
+                kind = ExplicitInitRule.Kind(rawValue: kindString) else {
+                    return []
+            }
+            return violationRangesInFile(file, dictionary: subDict) +
+                violationRangesInFile(file, kind: kind, dictionary: subDict)
+        }
+    }
+
+    private func violationRangesInFile(file: File) -> [NSRange] {
+        return violationRangesInFile(file, dictionary: file.structure.dictionary).sort { lh, rh in
+            lh.location > rh.location
+        }
+    }
+
+    public func correctFile(file: File) -> [Correction] {
+        let matches = violationRangesInFile(file)
+            .filter { !file.ruleEnabledViolatingRanges([$0], forRule: self).isEmpty }
+        guard !matches.isEmpty else { return [] }
+
+        let description = self.dynamicType.description
+        var corrections = [Correction]()
+        var contents = file.contents
+        for range in matches {
+            contents = (contents as NSString)
+                .stringByReplacingCharactersInRange(range, withString: "")
+            let location = Location(file: file, characterOffset: range.location)
+            corrections.append(Correction(ruleDescription: description, location: location))
+        }
+
+        file.write(contents)
+        return corrections
+    }
+}

SwiftLint.xcodeproj/project.pbxproj

@@ -55,6 +55,7 @@
 		6CCFCF301CFEF742003239EB /* Yaml.framework in Embed Frameworks into SwiftLintFramework.framework */ = {isa = PBXBuildFile; fileRef = E89376AC1B8A701E0025708E /* Yaml.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
 		7250948A1D0859260039B353 /* StatementPositionConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = 725094881D0855760039B353 /* StatementPositionConfiguration.swift */; };
 		78F032461D7C877E00BE709A /* OverridenSuperCallRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 78F032441D7C877800BE709A /* OverridenSuperCallRule.swift */; };
+		7C0C2E7A1D2866CB0076435A /* ExplicitInitRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7C0C2E791D2866CB0076435A /* ExplicitInitRule.swift */; };
 		78F032481D7D614300BE709A /* OverridenSuperCallConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = 78F032471D7D614300BE709A /* OverridenSuperCallConfiguration.swift */; };
 		83894F221B0C928A006214E1 /* RulesCommand.swift in Sources */ = {isa = PBXBuildFile; fileRef = 83894F211B0C928A006214E1 /* RulesCommand.swift */; };
 		83D71E281B131ECE000395DE /* RuleDescription.swift in Sources */ = {isa = PBXBuildFile; fileRef = 83D71E261B131EB5000395DE /* RuleDescription.swift */; };
@@ -228,6 +229,7 @@
 		6CC4259A1C77046200AEA885 /* SyntaxMap+SwiftLint.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "SyntaxMap+SwiftLint.swift"; sourceTree = "<group>"; };
 		725094881D0855760039B353 /* StatementPositionConfiguration.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = StatementPositionConfiguration.swift; sourceTree = "<group>"; };
 		78F032441D7C877800BE709A /* OverridenSuperCallRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = OverridenSuperCallRule.swift; sourceTree = "<group>"; };
+		7C0C2E791D2866CB0076435A /* ExplicitInitRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ExplicitInitRule.swift; sourceTree = "<group>"; };
 		78F032471D7D614300BE709A /* OverridenSuperCallConfiguration.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = OverridenSuperCallConfiguration.swift; sourceTree = "<group>"; };
 		83894F211B0C928A006214E1 /* RulesCommand.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = RulesCommand.swift; sourceTree = "<group>"; };
 		83D71E261B131EB5000395DE /* RuleDescription.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = RuleDescription.swift; sourceTree = "<group>"; };
@@ -614,6 +616,7 @@
 				3B1DF0111C5148140011BCED /* CustomRules.swift */,
 				2E02005E1C54BF680024D09D /* CyclomaticComplexityRule.swift */,
 				E847F0A81BFBBABD00EA9363 /* EmptyCountRule.swift */,
+				7C0C2E791D2866CB0076435A /* ExplicitInitRule.swift */,
 				E88DEA891B0992B300A66CB0 /* FileLengthRule.swift */,
 				E88DEA7F1B09903300A66CB0 /* ForceCastRule.swift */,
 				E816194D1BFBFEAB00946723 /* ForceTryRule.swift */,
@@ -964,6 +967,7 @@
 				D47A510E1DB29EEB00A4CC21 /* SwitchCaseOnNewlineRule.swift in Sources */,
 				E88DEA6F1B09843F00A66CB0 /* Location.swift in Sources */,
 				93E0C3CE1D67BD7F007FA25D /* ConditionalReturnsOnNewline.swift in Sources */,
+				7C0C2E7A1D2866CB0076435A /* ExplicitInitRule.swift in Sources */,
 				E88DEA771B098D0C00A66CB0 /* Rule.swift in Sources */,
 				24B4DF0D1D6DFDE90097803B /* RedundantNilCoalesingRule.swift in Sources */,
 				7250948A1D0859260039B353 /* StatementPositionConfiguration.swift in Sources */,

Tests/SwiftLintFramework/RulesTests.swift

@@ -113,6 +113,10 @@ class RulesTests: XCTestCase {
         verifyRule(EmptyCountRule.description)
     }
 
+    func testExplicitInit() {
+        verifyRule(ExplicitInitRule.description)
+    }
+
     func testFileLength() {
         verifyRule(FileLengthRule.description, commentDoesntViolate: false)
     }