Ensure newline after trailing line comments to prevent formatting issues

Author: TTOzzi

Sources/SwiftFormat/PrettyPrint/TokenStreamCreator.swift

@@ -3038,6 +3038,10 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
 
     if wasLineComment && !hasAppendedTrailingComment {
       trailingCommentTokens.forEach(appendToken)
+      hasAppendedTrailingComment = true
+    }
+    if hasAppendedTrailingComment {
+      appendNewlines(.hard)
     }
   }
 
@@ -3493,7 +3497,7 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
           generateEnableFormattingIfNecessary(position..<position + piece.sourceLength)
           appendToken(.comment(Comment(kind: .line, leadingIndent: leadingIndent, text: text), wasEndOfLine: false))
           generateDisableFormattingIfNecessary(position + piece.sourceLength)
-          appendNewlines(.soft)
+          appendNewlines(.hard)
           isStartOfFile = false
         }
         requiresNextNewline = true
@@ -3522,7 +3526,7 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
         generateEnableFormattingIfNecessary(position..<position + piece.sourceLength)
         appendToken(.comment(Comment(kind: .docLine, leadingIndent: leadingIndent, text: text), wasEndOfLine: false))
         generateDisableFormattingIfNecessary(position + piece.sourceLength)
-        appendNewlines(.soft)
+        appendNewlines(.hard)
         isStartOfFile = false
         requiresNextNewline = true
         leadingIndent = nil
@@ -3531,7 +3535,7 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
         generateEnableFormattingIfNecessary(position..<position + piece.sourceLength)
         appendToken(.comment(Comment(kind: .docBlock, leadingIndent: leadingIndent, text: text), wasEndOfLine: false))
         generateDisableFormattingIfNecessary(position + piece.sourceLength)
-        appendNewlines(.soft)
+        appendNewlines(.hard)
         isStartOfFile = false
         requiresNextNewline = false
         leadingIndent = nil
@@ -3651,7 +3655,15 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
       fatalError("Found non-break token at lastBreakIndex. TokenStreamCreator is invalid.")
     }
 
-    guard !canMergeNewlinesIntoLastBreak else {
+    let hasExistingHardNewline: Bool
+    switch existingNewlines {
+    case .elective, .soft, .escaped:
+      hasExistingHardNewline = false
+    case .hard:
+      hasExistingHardNewline = true
+    }
+
+    guard hasExistingHardNewline || !canMergeNewlinesIntoLastBreak else {
       tokens[lastBreakIndex] = .break(kind, size: size, newlines: existingNewlines + newlines)
       return
     }

Tests/SwiftFormatTests/PrettyPrint/AttributeTests.swift

@@ -623,4 +623,91 @@ final class AttributeTests: PrettyPrintTestCase {
 
     assertPrettyPrintEqual(input: input, expected: expected, linelength: 45)
   }
+
+  func testAttributesWithComment() {
+    let input =
+      """
+      @foo // comment
+      @bar
+      import Baz
+
+      """
+    let expected =
+      """
+      @foo  // comment
+      @bar import Baz
+
+      """
+
+    assertPrettyPrintEqual(input: input, expected: expected, linelength: 45)
+  }
+
+  func testAttributesConsecutiveComments() {
+    let input =
+      """
+      @foo // comment
+      // comment
+      @bar
+      import Baz
+
+      """
+    let expected =
+      """
+      @foo  // comment
+      // comment
+      @bar import Baz
+
+      """
+
+    assertPrettyPrintEqual(input: input, expected: expected, linelength: 45)
+  }
+
+  func testAttributesConsecutiveCommentsWithSomeNewlines() {
+    let input =
+      """
+      @foo // comment
+
+
+
+      // comment
+
+
+
+      @bar
+      let a = 1
+
+      """
+    let expected =
+      """
+      @foo  // comment
+
+      // comment
+
+      @bar
+      let a = 1
+
+      """
+
+    assertPrettyPrintEqual(input: input, expected: expected, linelength: 45)
+  }
+
+  func testAttributesWithLineAndBlockComments() {
+    let input =
+      """
+      @foo // comment
+      @bar /* comment */
+      @zoo // comment
+      import Baz
+
+      """
+    let expected =
+      """
+      @foo  // comment
+      @bar /* comment */ @zoo  // comment
+      import Baz
+
+      """
+
+    assertPrettyPrintEqual(input: input, expected: expected, linelength: 45)
+  }
 }