Merge pull request #92 from allevato/decl-trailing-comments

Handle end-of-line comments correctly in BlankLineBetweenMembers.

Author: allevato

Sources/SwiftFormatCore/Syntax+Convenience.swift

@@ -44,10 +44,19 @@ extension Syntax {
       // Iterate over the trivia, stopping at the first comment, and using that as the start
       // position.
       var currentPosition = firstToken.position
-      for piece in firstToken.leadingTrivia {
+      var sawNewline = false
+      loop: for piece in firstToken.leadingTrivia {
         switch piece {
-        case .lineComment, .blockComment, .docLineComment, .docBlockComment:
-          break
+        case .docLineComment,
+          .docBlockComment,
+          .lineComment where sawNewline,
+          .blockComment where sawNewline:
+          // Non-doc line or block comments before we've seen the first newline should actually be
+          // considered trailing comments of the previous line.
+          break loop
+        case .newlines, .carriageReturns, .carriageReturnLineFeeds:
+          sawNewline = true
+          fallthrough
         default:
           currentPosition += piece.sourceLength
         }

Sources/SwiftFormatRules/BlankLineBetweenMembers.swift

@@ -61,11 +61,10 @@ public final class BlankLineBetweenMembers: SyntaxFormatRule {
 
       let ignoreMember = ignoreSingleLine && isMemberSingleLine
       if (!previousMemberWasSingleLine || !ignoreMember) && !isLeadingBlankLinePresent(on: member) {
-        let blankLinePrefacedTrivia = Trivia.newlines(1) + (member.leadingTrivia ?? [])
         memberToAdd = replaceTrivia(
           on: memberToAdd,
           token: memberToAdd.firstToken,
-          leadingTrivia: blankLinePrefacedTrivia
+          leadingTrivia: blankLinePrefixedTrivia(member.leadingTrivia)
         ) as! MemberDeclListItemSyntax
         diagnose(.addBlankLine, on: member)
       }
@@ -80,6 +79,26 @@ public final class BlankLineBetweenMembers: SyntaxFormatRule {
     return node.withMembers(SyntaxFactory.makeMemberDeclList(membersList))
   }
 
+  /// Returns new trivia with a blank line inserted at the "beginning" of the given trivia, but
+  /// respecting any end-of-line comments associated with the previous line that may be present.
+  private func blankLinePrefixedTrivia(_ trivia: Trivia?) -> Trivia {
+    guard let trivia = trivia else { return .newlines(1) }
+
+    guard let firstNewlineIndex = trivia.firstIndex(where: {
+      switch $0 {
+      case .newlines, .carriageReturns, .carriageReturnLineFeeds:
+        return true
+      default:
+        return false
+      }
+    }) else {
+      return .newlines(1) + trivia
+    }
+
+    let newPieces = trivia[..<firstNewlineIndex] + [.newlines(1)] + trivia[firstNewlineIndex...]
+    return Trivia(pieces: newPieces).condensed()
+  }
+
   /// Returns whether any comments in the leading trivia of the given node are separated from the
   /// non-trivia tokens by at least 1 blank line.
   private func isLeadingTriviaSeparate(from node: Syntax) -> Bool {

Tests/SwiftFormatRulesTests/BlankLineBetweenMembersTests.swift

@@ -335,4 +335,31 @@ public class BlankLineBetweenMembersTests: DiagnosingTestCase {
       expected: expected,
       configuration: config)
   }
+
+  func testTrailingCommentsAreKeptTrailing() {
+    XCTAssertFormatting(
+      BlankLineBetweenMembers.self,
+      input:
+        """
+        enum Foo {
+          static let foo = "foo"  // foo
+          static let bar = "bar"  // bar
+          // this should move down
+          static let baz = "baz"  // baz
+          static let andSo = "should"  // this
+        }
+        """,
+      expected:
+        """
+        enum Foo {
+          static let foo = "foo"  // foo
+          static let bar = "bar"  // bar
+
+          // this should move down
+          static let baz = "baz"  // baz
+
+          static let andSo = "should"  // this
+        }
+        """)
+  }
 }

Tests/SwiftFormatRulesTests/XCTestManifests.swift

@@ -50,6 +50,7 @@ extension BlankLineBetweenMembersTests {
         ("testInvalidBlankLineBetweenMembers", testInvalidBlankLineBetweenMembers),
         ("testNestedMembers", testNestedMembers),
         ("testNoBlankLineBetweenSingleLineMembers", testNoBlankLineBetweenSingleLineMembers),
+        ("testTrailingCommentsAreKeptTrailing", testTrailingCommentsAreKeptTrailing),
         ("testTwoMembers", testTwoMembers),
     ]
 }