Add joined_default_parameter opt-in rule

to discourage explicit usage of the default separator. Implements realm#1093.
ornithocoder · Aug 3, 2017 · da823f5 · da823f5
1 parent 54d6199
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -15,6 +15,11 @@
   [Ornithologist Coder](https://github.com/ornithocoder)
   [#1370](https://github.com/realm/SwiftLint/issues/1370)
 
+* Add `joined_default_parameter` opt-in rule to discourage
+  explicit usage of the default separator.  
+  [Ornithologist Coder](https://github.com/ornithocoder)
+  [#1093](https://github.com/realm/SwiftLint/issues/1093)
+
 ##### Bug Fixes
 
 * Fix false positive on `force_unwrapping` rule when declaring

diff --git a/Rules.md b/Rules.md
@@ -41,6 +41,7 @@
 * [Implicit Getter](#implicit-getter)
 * [Implicit Return](#implicit-return)
 * [Implicitly Unwrapped Optional](#implicitly-unwrapped-optional)
+* [Joined Default Parameter](#joined-default-parameter)
 * [Large Tuple](#large-tuple)
 * [Leading Whitespace](#leading-whitespace)
 * [Legacy CGGeometry Functions](#legacy-cggeometry-functions)
@@ -4819,6 +4820,43 @@ func foo(int: Int!) {}
 
 
 
+## Joined Default Parameter
+
+Identifier | Enabled by default | Supports autocorrection | Kind 
+--- | --- | --- | ---
+`joined_default_parameter` | Disabled | No | idiomatic
+
+Discouraged explicit usage of the default separator.
+
+### Examples
+
+<details>
+<summary>Non Triggering Examples</summary>
+
+```swift
+let foo = bar.joined()
+```
+
+```swift
+let foo = bar.joined(separator: ",")
+```
+
+```swift
+let foo = bar.joined(separator: toto)
+```
+
+</details>
+<details>
+<summary>Triggering Examples</summary>
+
+```swift
+let foo = bar.joined(separator: "")
+```
+
+</details>
+
+
+
 ## Large Tuple
 
 Identifier | Enabled by default | Supports autocorrection | Kind 

diff --git a/Source/SwiftLintFramework/Models/MasterRuleList.swift b/Source/SwiftLintFramework/Models/MasterRuleList.swift
@@ -49,6 +49,7 @@ public let masterRuleList = RuleList(rules: [
     ImplicitGetterRule.self,
     ImplicitReturnRule.self,
     ImplicitlyUnwrappedOptionalRule.self,
+    JoinedDefaultParameterRule.self,
     LargeTupleRule.self,
     LeadingWhitespaceRule.self,
     LegacyCGGeometryFunctionsRule.self,

diff --git a/Source/SwiftLintFramework/Rules/JoinedDefaultRule.swift b/Source/SwiftLintFramework/Rules/JoinedDefaultRule.swift
@@ -0,0 +1,58 @@
+//
+//  JoinedDefaultRule.swift
+//  SwiftLint
+//
+//  Created by Ornithologist Coder on 8/3/17.
+//  Copyright © 2017 Realm. All rights reserved.
+//
+
+import Foundation
+import SourceKittenFramework
+
+public struct JoinedDefaultParameterRule: ASTRule, ConfigurationProviderRule, OptInRule {
+    public var configuration = SeverityConfiguration(.warning)
+
+    public init() {}
+
+    public static let description = RuleDescription(
+        identifier: "joined_default_parameter",
+        name: "Joined Default Parameter",
+        description: "Discouraged explicit usage of the default separator.",
+        kind: .idiomatic,
+        nonTriggeringExamples: [
+            "let foo = bar.joined()",
+            "let foo = bar.joined(separator: \",\")",
+            "let foo = bar.joined(separator: toto)"
+        ],
+        triggeringExamples: [
+            "let foo = bar.joined(separator: \"\")"
+        ]
+    )
+
+    public func validate(file: File,
+                         kind: SwiftExpressionKind,
+                         dictionary: [String: SourceKitRepresentable]) -> [StyleViolation] {
+        guard
+            kind == .call,
+            let offset = dictionary.offset,
+            let name = dictionary.name,
+            name.hasSuffix(".joined"),
+            passesDefaultSeparator(dictionary: dictionary, file: file)
+            else {
+                return []
+        }
+
+        return [StyleViolation(ruleDescription: type(of: self).description,
+                               severity: configuration.severity,
+                               location: Location(file: file, byteOffset: offset))]
+    }
+
+    private func passesDefaultSeparator(dictionary: [String: SourceKitRepresentable], file: File) -> Bool {
+        guard
+            let bodyOffset = dictionary.bodyOffset,
+            let bodyLength = dictionary.bodyLength else { return false }
+
+        let body = file.contents.bridge().substringWithByteRange(start: bodyOffset, length: bodyLength)
+        return body == "separator: \"\""
+    }
+}
diff --git a/SwiftLint.xcodeproj/project.pbxproj b/SwiftLint.xcodeproj/project.pbxproj
@@ -70,6 +70,7 @@
 		62622F6B1F2F2E3500D5D099 /* DiscouragedDirectInitRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 62622F6A1F2F2E3500D5D099 /* DiscouragedDirectInitRule.swift */; };
 		626D02971F31CBCC0054788D /* XCTFailMessageRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 626D02961F31CBCC0054788D /* XCTFailMessageRule.swift */; };
 		62A498561F306A7700D766E4 /* DiscouragedDirectInitConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = 62A498551F306A7700D766E4 /* DiscouragedDirectInitConfiguration.swift */; };
+		62A6E7931F3317E3003A0479 /* JoinedDefaultRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 62A6E7911F3317E3003A0479 /* JoinedDefaultRule.swift */; };
 		67932E2D1E54AF4B00CB0629 /* CyclomaticComplexityConfigurationTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 67932E2C1E54AF4B00CB0629 /* CyclomaticComplexityConfigurationTests.swift */; };
 		67EB4DFA1E4CC111004E9ACD /* CyclomaticComplexityConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = 67EB4DF81E4CC101004E9ACD /* CyclomaticComplexityConfiguration.swift */; };
 		67EB4DFC1E4CD7F5004E9ACD /* CyclomaticComplexityRuleTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 67EB4DFB1E4CD7F5004E9ACD /* CyclomaticComplexityRuleTests.swift */; };
@@ -377,6 +378,7 @@
 		62622F6A1F2F2E3500D5D099 /* DiscouragedDirectInitRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DiscouragedDirectInitRule.swift; sourceTree = "<group>"; };
 		626D02961F31CBCC0054788D /* XCTFailMessageRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = XCTFailMessageRule.swift; sourceTree = "<group>"; };
 		62A498551F306A7700D766E4 /* DiscouragedDirectInitConfiguration.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DiscouragedDirectInitConfiguration.swift; sourceTree = "<group>"; };
+		62A6E7911F3317E3003A0479 /* JoinedDefaultRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = JoinedDefaultRule.swift; sourceTree = "<group>"; };
 		62AF35D71F30B183009B11EE /* DiscouragedDirectInitRuleTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DiscouragedDirectInitRuleTests.swift; sourceTree = "<group>"; };
 		65454F451B14D73800319A6C /* ControlStatementRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ControlStatementRule.swift; sourceTree = "<group>"; };
 		67932E2C1E54AF4B00CB0629 /* CyclomaticComplexityConfigurationTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = CyclomaticComplexityConfigurationTests.swift; sourceTree = "<group>"; };
@@ -964,6 +966,7 @@
 				D43DB1071DC573DA00281215 /* ImplicitGetterRule.swift */,
 				47FF3BDF1E7C745100187E6D /* ImplicitlyUnwrappedOptionalRule.swift */,
 				D4470D561EB69225008A1B2E /* ImplicitReturnRule.swift */,
+				62A6E7911F3317E3003A0479 /* JoinedDefaultRule.swift */,
 				D4DA1DF91E18D6200037413D /* LargeTupleRule.swift */,
 				E88DEA7D1B098F2A00A66CB0 /* LeadingWhitespaceRule.swift */,
 				4DB7815C1CAD690100BC4723 /* LegacyCGGeometryFunctionsRule.swift */,
@@ -1440,6 +1443,7 @@
 				C328A2F71E6759AE00A9E4D7 /* ExplicitTypeInterfaceRule.swift in Sources */,
 				93E0C3CE1D67BD7F007FA25D /* ConditionalReturnsOnNewlineRule.swift in Sources */,
 				D43DB1081DC573DA00281215 /* ImplicitGetterRule.swift in Sources */,
+				62A6E7931F3317E3003A0479 /* JoinedDefaultRule.swift in Sources */,
 				D4FD4C851F2A260A00DD8AA8 /* BlockBasedKVORule.swift in Sources */,
 				7C0C2E7A1D2866CB0076435A /* ExplicitInitRule.swift in Sources */,
 				E88DEA771B098D0C00A66CB0 /* Rule.swift in Sources */,

diff --git a/Tests/LinuxMain.swift b/Tests/LinuxMain.swift
@@ -367,6 +367,7 @@ extension RulesTests {
         ("testImplicitGetter", testImplicitGetter),
         ("testImplicitlyUnwrappedOptional", testImplicitlyUnwrappedOptional),
         ("testImplicitReturn", testImplicitReturn),
+        ("testJoinedDefaultParameter", testJoinedDefaultParameter),
         ("testLargeTuple", testLargeTuple),
         ("testLeadingWhitespace", testLeadingWhitespace),
         ("testLegacyCGGeometryFunctions", testLegacyCGGeometryFunctions),

diff --git a/Tests/SwiftLintFrameworkTests/RulesTests.swift b/Tests/SwiftLintFrameworkTests/RulesTests.swift
@@ -142,6 +142,10 @@ class RulesTests: XCTestCase {
         verifyRule(ImplicitReturnRule.description)
     }
 
+    func testJoinedDefaultParameter() {
+        verifyRule(JoinedDefaultParameterRule.description)
+    }
+
     func testLargeTuple() {
         verifyRule(LargeTupleRule.description)
     }