Add empty_collection_literal rule

dchohfi · Aug 29, 2019 · 130371b · 130371b
1 parent 0d18758
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -23,6 +23,10 @@
   expressions like `filter(where:).isEmpty` instead of `contains(where:)`.  
   [Marcelo Fabri](https://github.com/marcelofabri)
 
+* Add `empty_collection_literal` opt-in rule to prefer using `isEmpty` to comparison to `[]` or `[:]`.  
+  [Colton Schlosser](https://github.com/cltnschlosser)
+  [#2807](https://github.com/realm/SwiftLint/issues/2807)
+
 #### Bug Fixes
 
 * Fixed false positive in `colon` rule inside guard and ternary operator.  

diff --git a/Rules.md b/Rules.md
@@ -32,6 +32,7 @@
 * [Duplicate Enum Cases](#duplicate-enum-cases)
 * [Duplicate Imports](#duplicate-imports)
 * [Dynamic Inline](#dynamic-inline)
+* [Empty Collection Literal](#empty-collection-literal)
 * [Empty Count](#empty-count)
 * [Empty Enum Arguments](#empty-enum-arguments)
 * [Empty Parameters](#empty-parameters)
@@ -5398,6 +5399,75 @@ dynamic
 
 
 
+## Empty Collection Literal
+
+Identifier | Enabled by default | Supports autocorrection | Kind | Analyzer | Minimum Swift Compiler Version
+--- | --- | --- | --- | --- | ---
+`empty_collection_literal` | Disabled | No | performance | No | 3.0.0 
+
+Prefer checking `isEmpty` over comparing collection to an empty array or dictionary literal.
+
+### Examples
+
+<details>
+<summary>Non Triggering Examples</summary>
+
+```swift
+myArray = []
+```
+
+```swift
+myArray.isEmpty
+```
+
+```swift
+!myArray.isEmpy
+```
+
+```swift
+myDict = [:]
+```
+
+</details>
+<details>
+<summary>Triggering Examples</summary>
+
+```swift
+myArray↓ == []
+```
+
+```swift
+myArray↓ != []
+```
+
+```swift
+myArray↓ == [ ]
+```
+
+```swift
+myDict↓ == [:]
+```
+
+```swift
+myDict↓ != [:]
+```
+
+```swift
+myDict↓ == [: ]
+```
+
+```swift
+myDict↓ == [ :]
+```
+
+```swift
+myDict↓ == [ : ]
+```
+
+</details>
+
+
+
 ## Empty Count
 
 Identifier | Enabled by default | Supports autocorrection | Kind | Analyzer | Minimum Swift Compiler Version

diff --git a/Source/SwiftLintFramework/Models/MasterRuleList.swift b/Source/SwiftLintFramework/Models/MasterRuleList.swift
@@ -1,4 +1,4 @@
-// Generated using Sourcery 0.16.2 — https://github.com/krzysztofzablocki/Sourcery
+// Generated using Sourcery 0.16.1 — https://github.com/krzysztofzablocki/Sourcery
 // DO NOT EDIT
 
 public let masterRuleList = RuleList(rules: [
@@ -33,6 +33,7 @@ public let masterRuleList = RuleList(rules: [
     DuplicateEnumCasesRule.self,
     DuplicateImportsRule.self,
     DynamicInlineRule.self,
+    EmptyCollectionLiteralRule.self,
     EmptyCountRule.self,
     EmptyEnumArgumentsRule.self,
     EmptyParametersRule.self,

diff --git a/Source/SwiftLintFramework/Rules/Performance/EmptyCollectionLiteralRule.swift b/Source/SwiftLintFramework/Rules/Performance/EmptyCollectionLiteralRule.swift
@@ -0,0 +1,40 @@
+import SourceKittenFramework
+
+public struct EmptyCollectionLiteralRule: ConfigurationProviderRule, OptInRule, AutomaticTestableRule {
+    public var configuration = SeverityConfiguration(.warning)
+
+    public init() {}
+
+    public static let description = RuleDescription(
+        identifier: "empty_collection_literal",
+        name: "Empty Collection Literal",
+        description: "Prefer checking `isEmpty` over comparing collection to an empty array or dictionary literal.",
+        kind: .performance,
+        nonTriggeringExamples: [
+            "myArray = []",
+            "myArray.isEmpty",
+            "!myArray.isEmpy",
+            "myDict = [:]"
+        ],
+        triggeringExamples: [
+            "myArray↓ == []",
+            "myArray↓ != []",
+            "myArray↓ == [ ]",
+            "myDict↓ == [:]",
+            "myDict↓ != [:]",
+            "myDict↓ == [: ]",
+            "myDict↓ == [ :]",
+            "myDict↓ == [ : ]"
+        ]
+    )
+
+    public func validate(file: File) -> [StyleViolation] {
+        let pattern = "\\b\\s*(==|!=)\\s*\\[\\s*:?\\s*\\]"
+        let excludingKinds = SyntaxKind.commentAndStringKinds
+        return file.match(pattern: pattern, excludingSyntaxKinds: excludingKinds).map {
+            StyleViolation(ruleDescription: type(of: self).description,
+                           severity: configuration.severity,
+                           location: Location(file: file, characterOffset: $0.location))
+        }
+    }
+}
diff --git a/SwiftLint.xcodeproj/project.pbxproj b/SwiftLint.xcodeproj/project.pbxproj
@@ -90,6 +90,7 @@
 		4DB7815E1CAD72BA00BC4723 /* LegacyCGGeometryFunctionsRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4DB7815C1CAD690100BC4723 /* LegacyCGGeometryFunctionsRule.swift */; };
 		4DCB8E7F1CBE494E0070FCF0 /* RegexHelpers.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4DCB8E7D1CBE43640070FCF0 /* RegexHelpers.swift */; };
 		4E342B4C2215C793008E4EF8 /* ReduceBooleanRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4E342B4A2215C6DF008E4EF8 /* ReduceBooleanRule.swift */; };
+		550DA0E022DB95AD00B67F03 /* EmptyCollectionLiteralRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = 550DA0DE22DB958400B67F03 /* EmptyCollectionLiteralRule.swift */; };
 		57ED827B1CF656E3002B3513 /* JUnitReporter.swift in Sources */ = {isa = PBXBuildFile; fileRef = 57ED82791CF65183002B3513 /* JUnitReporter.swift */; };
 		584B0D3A2112BA78002F7E25 /* SonarQubeReporter.swift in Sources */ = {isa = PBXBuildFile; fileRef = 584B0D392112BA78002F7E25 /* SonarQubeReporter.swift */; };
 		584B0D3C2112E8FB002F7E25 /* CannedSonarQubeReporterOutput.json in Resources */ = {isa = PBXBuildFile; fileRef = 584B0D3B2112E8FB002F7E25 /* CannedSonarQubeReporterOutput.json */; };
@@ -569,6 +570,7 @@
 		4E342B4A2215C6DF008E4EF8 /* ReduceBooleanRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ReduceBooleanRule.swift; sourceTree = "<group>"; };
 		5499CA961A2394B700783309 /* Components.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Components.plist; sourceTree = "<group>"; };
 		5499CA971A2394B700783309 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
+		550DA0DE22DB958400B67F03 /* EmptyCollectionLiteralRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = EmptyCollectionLiteralRule.swift; sourceTree = "<group>"; };
 		57ED82791CF65183002B3513 /* JUnitReporter.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = JUnitReporter.swift; sourceTree = "<group>"; };
 		584B0D392112BA78002F7E25 /* SonarQubeReporter.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SonarQubeReporter.swift; sourceTree = "<group>"; };
 		584B0D3B2112E8FB002F7E25 /* CannedSonarQubeReporterOutput.json */ = {isa = PBXFileReference; lastKnownFileType = text.json; path = CannedSonarQubeReporterOutput.json; sourceTree = "<group>"; };
@@ -1079,6 +1081,7 @@
 				29AD4C641F6EA16C009B66E1 /* ContainsOverFirstNotNilRule.swift */,
 				D489B546231233490090BAA0 /* ContainsOverFilterCountRule.swift */,
 				D489B549231383350090BAA0 /* ContainsOverFilterIsEmptyRule.swift */,
+				550DA0DE22DB958400B67F03 /* EmptyCollectionLiteralRule.swift */,
 				E847F0A81BFBBABD00EA9363 /* EmptyCountRule.swift */,
 				740DF1AF203F5AFC0081F694 /* EmptyStringRule.swift */,
 				D42D2B371E09CC0D00CD7A2E /* FirstWhereRule.swift */,
@@ -2025,6 +2028,7 @@
 				125AAC78203AA82D0004BCE0 /* ExplicitTypeInterfaceConfiguration.swift in Sources */,
 				1E18574B1EADBA51004F89F7 /* NoExtensionAccessModifierRule.swift in Sources */,
 				D42D2B381E09CC0D00CD7A2E /* FirstWhereRule.swift in Sources */,
+				550DA0E022DB95AD00B67F03 /* EmptyCollectionLiteralRule.swift in Sources */,
 				D4B0226F1E0C75F9007E5297 /* VerticalParameterAlignmentRule.swift in Sources */,
 				E8BDE3FF1EDF91B6002EC12F /* RuleList.swift in Sources */,
 				E889D8C71F1D357B00058332 /* Configuration+Merging.swift in Sources */,

diff --git a/Tests/LinuxMain.swift b/Tests/LinuxMain.swift
@@ -346,6 +346,12 @@ extension DynamicInlineRuleTests {
     ]
 }
 
+extension EmptyCollectionLiteralRuleTests {
+    static var allTests: [(String, (EmptyCollectionLiteralRuleTests) -> () throws -> Void)] = [
+        ("testWithDefaultConfiguration", testWithDefaultConfiguration)
+    ]
+}
+
 extension EmptyCountRuleTests {
     static var allTests: [(String, (EmptyCountRuleTests) -> () throws -> Void)] = [
         ("testWithDefaultConfiguration", testWithDefaultConfiguration)
@@ -1582,6 +1588,7 @@ XCTMain([
     testCase(DuplicateEnumCasesRuleTests.allTests),
     testCase(DuplicateImportsRuleTests.allTests),
     testCase(DynamicInlineRuleTests.allTests),
+    testCase(EmptyCollectionLiteralRuleTests.allTests),
     testCase(EmptyCountRuleTests.allTests),
     testCase(EmptyEnumArgumentsRuleTests.allTests),
     testCase(EmptyParametersRuleTests.allTests),

diff --git a/Tests/SwiftLintFrameworkTests/AutomaticRuleTests.generated.swift b/Tests/SwiftLintFrameworkTests/AutomaticRuleTests.generated.swift
@@ -126,6 +126,12 @@ class DynamicInlineRuleTests: XCTestCase {
     }
 }
 
+class EmptyCollectionLiteralRuleTests: XCTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(EmptyCollectionLiteralRule.description)
+    }
+}
+
 class EmptyCountRuleTests: XCTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(EmptyCountRule.description)