Merge pull request swiftlang#146 from google/no-space-after-line-comment-sigil

Make CommentWhitespace a lint-only rule.

Author: dabelknap

Diff for: Sources/SwiftFormatRules/CommentWhitespace.swift

@@ -10,109 +10,46 @@
 //
 //===----------------------------------------------------------------------===//
 
-import Foundation
 import SwiftFormatCore
 import SwiftSyntax
 
-/// At least two spaces before, and exactly one space after the `//` that begins a line comment.
+/// There are at least two spaces before the `//` that begins a line comment.
 ///
-/// Lint: If an invalid number of spaces appear before or after a comment, a lint error is
-///       raised.
-///
-/// Format: All comments will have at least 2 spaces before, and a single space after, the `//`.
+/// Lint: If an invalid number of spaces appear before a comment, a lint error is raised.
 ///
 /// - SeeAlso: https://google.github.io/swift#horizontal-whitespace
-public final class CommentWhitespace: SyntaxFormatRule {
-  public override func visit (_ token: TokenSyntax) -> Syntax {
-    var pieces = [TriviaPiece]()
-    var validToken = token
-    var needsWhitespaceFix = false
+public final class CommentWhitespace: SyntaxLintRule {
 
-    guard let nextToken = token.nextToken else {
-      // In the case there is a line comment at the end of the file, it ensures
-      // that the line comment has a single space after the `//`.
-      pieces = checksSpacesAfterLineComment(isInvalid: &needsWhitespaceFix, token: token)
-      return needsWhitespaceFix ? token.withLeadingTrivia(Trivia.init(pieces: pieces)) : token
-    }
+  public override func visit(_ token: TokenSyntax) {
+    guard let nextToken = token.nextToken else { return }
 
-    // Ensures the line comment has at least 2 spaces before the `//`.
-    if hasInlineLineComment(trivia: nextToken.leadingTrivia) {
-      let numSpaces = token.trailingTrivia.numberOfSpaces
-      if numSpaces < 2 {
-        needsWhitespaceFix = true
-        let addSpaces = 2 - numSpaces
-        diagnose(.addSpacesBeforeLineComment(count: addSpaces), on:token)
-        validToken = token.withTrailingTrivia(token.trailingTrivia.appending(.spaces(addSpaces)))
+    // Ensures the line comment has at least two spaces before the `//`.
+    if triviaIsEndOfLineComment(nextToken.leadingTrivia) {
+      let numberOfSpaces = token.trailingTrivia.numberOfSpaces
+      if numberOfSpaces < 2 {
+        let spacesToAdd = 2 - numberOfSpaces
+        diagnose(.addSpacesBeforeLineComment(count: spacesToAdd), on: token)
       }
     }
-
-    pieces = checksSpacesAfterLineComment(isInvalid: &needsWhitespaceFix, token: token)
-    return needsWhitespaceFix ? validToken.withLeadingTrivia(Trivia.init(pieces: pieces)) : token
   }
 
-  /// Returns a boolean indicating if the given trivia contains
-  /// a line comment inline with code.
-  private func hasInlineLineComment (trivia: Trivia) -> Bool {
-    // Comments are inline unless the trivia begins with a
-    // with a newline.
+  /// Returns a value indicating whether the given trivia represents an end of line comment.
+  private func triviaIsEndOfLineComment(_ trivia: Trivia) -> Bool {
+    // Comments are end-of-line unless the trivia begins with a newline.
     if let firstPiece = trivia.reversed().last {
-      if case .newlines(_) = firstPiece {
-        return false
-      }
+      if case .newlines(_) = firstPiece { return false }
     }
     for piece in trivia {
-      if case .lineComment(_) = piece {
-        return true
-      }
+      if case .lineComment(_) = piece { return true }
     }
     return false
   }
-
-  /// Ensures the line comment has exactly one space after the `//`.
-  private func checksSpacesAfterLineComment(isInvalid: inout Bool, token: TokenSyntax) -> [TriviaPiece] {
-    var pieces = [TriviaPiece]()
-
-    for piece in token.leadingTrivia {
-      // Checks if the line comment has exactly one space after the `//`,
-      // if it doesn't it removes or add an space, depending on what the
-      // comment needs in order to follow the right format.
-      if case .lineComment(let text) = piece,
-         let formatText = formatLineComment(textLineComment: text, token: token) {
-        isInvalid = true
-        pieces.append(TriviaPiece.lineComment(formatText))
-      }
-      else {
-        pieces.append(piece)
-      }
-    }
-    return pieces
-  }
-
-  /// Given a string with the text of a line comment, it ensures there
-  /// is exactly one space after the `//`. If the string doesn't follow
-  /// this rule a new string is returned with the right format.
-  private func formatLineComment (textLineComment: String, token: TokenSyntax) -> String? {
-    let text = textLineComment.dropFirst(2)
-    if text.first != " " {
-      diagnose(.addSpaceAfterLineComment, on: token)
-      return "// " + text.trimmingCharacters(in: .whitespaces)
-    }
-    else if text.dropFirst(1).first == " " {
-      diagnose(.removeSpacesAfterLineComment, on: token)
-      return "// " + text.trimmingCharacters(in: .whitespaces)
-    }
-    return nil
-  }
 }
 
 extension Diagnostic.Message {
+
   static func addSpacesBeforeLineComment(count: Int) -> Diagnostic.Message {
     let ending = count == 1 ? "" : "s"
     return Diagnostic.Message(.warning, "add \(count) space\(ending) before the //")
   }
-
-  static let addSpaceAfterLineComment =
-    Diagnostic.Message(.warning, "add one space after `//`")
-  static let removeSpacesAfterLineComment =
-    Diagnostic.Message(.warning, "remove excess of spaces after the `//`")
 }