Add rule for single space after period on comments (#4624)

.swiftlint.yml

@@ -48,6 +48,7 @@ opt_in_rules:
   - overridden_super_call
   - override_in_extension
   - pattern_matching_keywords
+  - period_spacing
   - prefer_self_type_over_type_of_self
   - private_action
   - private_outlet

CHANGELOG.md

@@ -49,6 +49,11 @@
   `single_test_class` and `empty_xctest_method` rules.  
   [Martin Redington](https://github.com/mildm8nnered)
   [#4200](https://github.com/realm/SwiftLint/issues/4200)
+  
+  * Add `period_spacing` opt-in rule that checks periods are not followed
+  by 2 or more spaces in comments.  
+  [Julioacarrettoni](https://github.com/Julioacarrettoni)
+  [#4624](https://github.com/realm/SwiftLint/pull/4624)
 
 * Show warnings in the console for Analyzer rules that are listed in the
   `opt_in_rules` configuration section.  

Source/SwiftLintFramework/Extensions/SyntaxClassification+isComment.swift

@@ -0,0 +1,15 @@
+import IDEUtils
+
+extension SyntaxClassification {
+    // True if it is any kind of comment.
+    var isComment: Bool {
+        switch self {
+        case .lineComment, .docLineComment, .blockComment, .docBlockComment:
+            return true
+        case .none, .keyword, .identifier, .typeIdentifier, .operatorIdentifier, .dollarIdentifier, .integerLiteral,
+             .floatingLiteral, .stringLiteral, .stringInterpolationAnchor, .poundDirectiveKeyword, .buildConfigId,
+             .attribute, .objectLiteral, .editorPlaceholder:
+            return false
+        }
+    }
+}

Source/SwiftLintFramework/Models/PrimaryRuleList.swift

@@ -137,6 +137,7 @@ public let primaryRuleList = RuleList(rules: [
     OverriddenSuperCallRule.self,
     OverrideInExtensionRule.self,
     PatternMatchingKeywordsRule.self,
+    PeriodSpacingRule.self,
     PreferNimbleRule.self,
     PreferSelfInStaticReferencesRule.self,
     PreferSelfTypeOverTypeOfSelfRule.self,

Source/SwiftLintFramework/Rules/Lint/CommentSpacingRule.swift

@@ -122,15 +122,9 @@ struct CommentSpacingRule: SourceKitFreeRule, ConfigurationProviderRule, Substit
     func violationRanges(in file: SwiftLintFile) -> [NSRange] {
         // Find all comment tokens in the file and regex search them for violations
         file.syntaxClassifications
-            .compactMap { (classifiedRange: SyntaxClassifiedRange) -> [NSRange]? in
-                switch classifiedRange.kind {
-                case .blockComment, .docBlockComment, .lineComment, .docLineComment:
-                    break
-                default:
-                    return nil
-                }
-
-                let range = classifiedRange.range.toSourceKittenByteRange()
+            .filter(\.kind.isComment)
+            .map { $0.range.toSourceKittenByteRange() }
+            .compactMap { (range: ByteRange) -> [NSRange]? in
                 return file.stringView
                     .substringWithByteRange(range)
                     .map(StringView.init)

Source/SwiftLintFramework/Rules/Lint/PeriodSpacingRule.swift

@@ -0,0 +1,94 @@
+import Foundation
+import IDEUtils
+import SourceKittenFramework
+
+struct PeriodSpacingRule: SourceKitFreeRule, ConfigurationProviderRule, OptInRule, SubstitutionCorrectableRule {
+    var configuration = SeverityConfiguration(.warning)
+
+    init() {}
+
+    static let description = RuleDescription(
+        identifier: "period_spacing",
+        name: "Period Spacing",
+        description: "Periods should not be followed by more than one space.",
+        kind: .style,
+        nonTriggeringExamples: [
+            Example("let pi = 3.2"),
+            Example("let pi = Double.pi"),
+            Example("let pi = Double. pi"),
+            Example("let pi = Double.  pi"),
+            Example("// A. Single."),
+            Example("///   - code: Identifier of the error. Integer."),
+            Example("""
+            // value: Multiline.
+            //        Comment.
+            """),
+            Example("""
+            /**
+            Sentence ended in period.
+
+            - Sentence 2 new line characters after.
+            **/
+            """)
+        ],
+        triggeringExamples: [
+            Example("/* Only god knows why. ↓ This symbol does nothing. */", testWrappingInComment: false),
+            Example("// Only god knows why. ↓ This symbol does nothing.", testWrappingInComment: false),
+            Example("// Single. Double. ↓ End.", testWrappingInComment: false),
+            Example("// Single. Double. ↓ Triple. ↓  End.", testWrappingInComment: false),
+            Example("// Triple. ↓  Quad. ↓   End.", testWrappingInComment: false),
+            Example("///   - code: Identifier of the error. ↓ Integer.", testWrappingInComment: false)
+        ],
+        corrections: [
+            Example("/* Why. ↓ Symbol does nothing. */"): Example("/* Why. Symbol does nothing. */"),
+            Example("// Why. ↓ Symbol does nothing."): Example("// Why. Symbol does nothing."),
+            Example("// Single. Double. ↓ End."): Example("// Single. Double. End."),
+            Example("// Single. Double. ↓ Triple. ↓  End."): Example("// Single. Double. Triple. End."),
+            Example("// Triple. ↓  Quad. ↓   End."): Example("// Triple. Quad. End."),
+            Example("///   - code: Identifier. ↓ Integer."): Example("///   - code: Identifier. Integer.")
+        ]
+    )
+
+    func violationRanges(in file: SwiftLintFile) -> [NSRange] {
+        // Find all comment tokens in the file and regex search them for violations
+        file.syntaxClassifications
+            .filter(\.kind.isComment)
+            .map { $0.range.toSourceKittenByteRange() }
+            .compactMap { (range: ByteRange) -> [NSRange]? in
+                return file.stringView
+                    .substringWithByteRange(range)
+                    .map(StringView.init)
+                    .map { commentBody in
+                        // Look for a period followed by two or more whitespaces but not new line or carriage returns
+                        return regex(#"\.[^\S\r\n]{2,}"#)
+                            .matches(in: commentBody)
+                            .compactMap { result in
+                                // Set the location to start from the second whitespace till the last one.
+                                return file.stringView.byteRangeToNSRange(
+                                    ByteRange(
+                                        // Safe to mix NSRange offsets with byte offsets here because the
+                                        // regex can't contain multi-byte characters
+                                        location: ByteCount(range.lowerBound.value + result.range.lowerBound + 2),
+                                        length: ByteCount(result.range.length.advanced(by: -2))
+                                    )
+                                )
+                            }
+                    }
+            }
+            .flatMap { $0 }
+    }
+
+    func validate(file: SwiftLintFile) -> [StyleViolation] {
+        return violationRanges(in: file).map { range in
+            StyleViolation(
+                ruleDescription: Self.description,
+                severity: configuration.severity,
+                location: Location(file: file, characterOffset: range.location)
+            )
+        }
+    }
+
+    func substitution(for violationRange: NSRange, in file: SwiftLintFile) -> (NSRange, String)? {
+        return (violationRange, "")
+    }
+}

Tests/GeneratedTests/GeneratedTests.swift

@@ -811,6 +811,12 @@ class PatternMatchingKeywordsRuleGeneratedTests: XCTestCase {
     }
 }
 
+class PeriodSpacingRuleGeneratedTests: XCTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(PeriodSpacingRule.description)
+    }
+}
+
 class PreferNimbleRuleGeneratedTests: XCTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(PreferNimbleRule.description)