Merge adjacent .line and .docLine comments into a single element.

Author: shawnhyam

Sources/SwiftFormat/PrettyPrint/Comment.swift

@@ -64,7 +64,7 @@ struct Comment {
 
     switch kind {
     case .line, .docLine:
-      self.text = [text.trimmingTrailingWhitespace()]
+      self.text = [text]
       self.text[0].removeFirst(kind.prefixLength)
       self.length = self.text.reduce(0, { $0 + $1.count + kind.prefixLength + 1 })
 
@@ -88,8 +88,9 @@ struct Comment {
   func print(indent: [Indent]) -> String {
     switch self.kind {
     case .line, .docLine:
-      let separator = "\n" + kind.prefix
-      return kind.prefix + self.text.joined(separator: separator)
+      let separator = "\n" + indent.indentation() + kind.prefix
+      let trimmedLines = self.text.map { $0.trimmingTrailingWhitespace() }
+      return kind.prefix + trimmedLines.joined(separator: separator)
     case .block, .docBlock:
       let separator = "\n"
       return kind.prefix + self.text.joined(separator: separator) + "*/"

Sources/SwiftFormat/PrettyPrint/TokenStreamCreator.swift

@@ -3386,12 +3386,31 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
   private func appendToken(_ token: Token) {
     if let last = tokens.last {
       switch (last, token) {
-      case (.comment(let c1, _), .comment(let c2, _))
-      where c1.kind == .docLine && c2.kind == .docLine:
-        var newComment = c1
-        newComment.addText(c2.text)
-        tokens[tokens.count - 1] = .comment(newComment, wasEndOfLine: false)
-        return
+      case (.break(.same, _, .soft(let count, _)), .comment(let c2, _))
+        where count == 1 && (c2.kind == .docLine || c2.kind == .line):
+        // we are search for the pattern of [line comment] - [soft break 1] - [line comment]
+        // where the comment type is the same; these can be merged into a single comment
+        if let nextToLast = tokens.dropLast().last,
+          case let .comment(c1, false) = nextToLast, 
+          c1.kind == c2.kind
+        {
+          var mergedComment = c1
+          mergedComment.addText(c2.text)
+          tokens.removeLast()  // remove the soft break
+          // replace the original comment with the merged one
+          tokens[tokens.count - 1] = .comment(mergedComment, wasEndOfLine: false)
+
+          // need to fix lastBreakIndex because we just removed the last break
+          lastBreakIndex = tokens.lastIndex(where: {
+            switch $0 {
+            case .break: return true
+            default: return false
+            }
+          })
+          canMergeNewlinesIntoLastBreak = false
+
+          return
+        }
 
       // If we see a pair of spaces where one or both are flexible, combine them into a new token
       // with the maximum of their counts.