Fix missing newline in member macro

Author: kimdv

Sources/SwiftParser/ParseSourceFile.swift

@@ -152,8 +152,9 @@ extension Parser {
     }
 
     let remainingTokens = self.consumeRemainingTokens()
+
     if remainingTokens.isEmpty {
-      return into
+      return R.init(transferTrailingTrivaFromEndOfFileIfPresent(raw: into.raw))!
     }
 
     let existingUnexpected: [RawSyntax]
@@ -166,6 +167,33 @@ extension Parser {
     let unexpected = RawUnexpectedNodesSyntax(elements: existingUnexpected + remainingTokens, arena: self.arena)
 
     let withUnexpected = layout.replacingChild(at: layout.children.count - 1, with: unexpected.raw, arena: self.arena)
-    return R.init(withUnexpected)!
+
+    return R.init(transferTrailingTrivaFromEndOfFileIfPresent(raw: withUnexpected))!
+  }
+
+  /// Parses the end-of-file token and appends its leading trivia to the provided `RawSyntax`.
+  /// - Parameter raw: The raw syntax node to which the leading trivia of the end-of-file token will be appended.
+  /// - Returns: An instance of the generic type `R` if the end-of-file token is present, or `nil` otherwise.
+  private mutating func transferTrailingTrivaFromEndOfFileIfPresent(raw: RawSyntax) -> RawSyntax {
+    if let endOfFileToken = self.consume(if: .endOfFile),
+      !endOfFileToken.leadingTriviaPieces.isEmpty,
+      let raw = raw.withTrailingTrivia(
+        Trivia(
+          rawPieces: (raw.trailingTriviaPieces ?? []) + endOfFileToken.leadingTriviaPieces
+        ),
+        arena: self.arena
+      )
+    {
+      return raw
+    } else {
+      return raw
+    }
+  }
+}
+
+private extension Trivia {
+  init(rawPieces: [RawTriviaPiece]) {
+    let pieces = rawPieces.map(TriviaPiece.init(raw:))
+    self.init(pieces: pieces)
   }
 }

Sources/SwiftSyntax/Raw/RawSyntax.swift

@@ -302,6 +302,7 @@ extension RawSyntax {
   /// - Parameters:
   ///   - leadingTrivia: The trivia to attach.
   ///   - arena: SyntaxArena to the result node data resides.
+  @_spi(RawSyntax)
   func withLeadingTrivia(_ leadingTrivia: Trivia, arena: SyntaxArena) -> RawSyntax? {
     switch view {
     case .token(let tokenView):
@@ -328,7 +329,8 @@ extension RawSyntax {
   /// - Parameters:
   ///   - trailingTrivia: The trivia to attach.
   ///   - arena: SyntaxArena to the result node data resides.
-  func withTrailingTrivia(_ trailingTrivia: Trivia, arena: SyntaxArena) -> RawSyntax? {
+  @_spi(RawSyntax)
+  public func withTrailingTrivia(_ trailingTrivia: Trivia, arena: SyntaxArena) -> RawSyntax? {
     switch view {
     case .token(let tokenView):
       return .makeMaterializedToken(

Tests/SwiftParserTest/DeclarationTests.swift

@@ -3120,4 +3120,17 @@ final class DeclarationTests: ParserTestCase {
       experimentalFeatures: .nonEscapableTypes
     )
   }
+
+  func testDeclarationEndingWithNewline() {
+    let inputs: [UInt: String] = [
+      #line: "var x = 0\n",
+      #line: "var x = 0 garbage\n",
+      #line: "var x = 0 \n",
+    ]
+
+    for (line, input) in inputs {
+      let decl = DeclSyntax(stringLiteral: input)
+      XCTAssertEqual(decl.description, input, line: line)
+    }
+  }
 }

Tests/SwiftSyntaxMacroExpansionTest/MemberMacroTests.swift

@@ -299,4 +299,64 @@ final class MemberMacroTests: XCTestCase {
       ]
     )
   }
+
+  func testAddMemberToEmptyDeclaration() {
+    struct TestMacro: MemberMacro {
+      static func expansion(
+        of node: AttributeSyntax,
+        providingMembersOf declaration: some DeclGroupSyntax,
+        conformingTo protocols: [TypeSyntax],
+        in context: some MacroExpansionContext
+      ) throws -> [DeclSyntax] {
+        return [DeclSyntax("var x = 0")]
+      }
+    }
+
+    assertMacroExpansion(
+      """
+      @Test
+      struct Foo {}
+      """,
+      expandedSource: """
+        struct Foo {
+
+          var x = 0
+        }
+        """,
+      macros: [
+        "Test": TestMacro.self
+      ],
+      indentationWidth: indentationWidth
+    )
+  }
+
+  func testAddMemberToEmptyDeclarationWithEndingNewline() {
+    struct TestMacro: MemberMacro {
+      static func expansion(
+        of node: AttributeSyntax,
+        providingMembersOf declaration: some DeclGroupSyntax,
+        conformingTo protocols: [TypeSyntax],
+        in context: some MacroExpansionContext
+      ) throws -> [DeclSyntax] {
+        return [DeclSyntax("var x = 0\n")]
+      }
+    }
+
+    assertMacroExpansion(
+      """
+      @Test
+      struct Foo {}
+      """,
+      expandedSource: """
+        struct Foo {
+
+          var x = 0
+        }
+        """,
+      macros: [
+        "Test": TestMacro.self
+      ],
+      indentationWidth: indentationWidth
+    )
+  }
 }

Tests/SwiftSyntaxMacroExpansionTest/PeerMacroTests.swift

@@ -151,7 +151,7 @@ final class PeerMacroTests: XCTestCase {
           Task {
             completionHandler(await f(a: a, for: b, value))
           }
-        }
+          }
         """,
       macros: ["addCompletionHandler": AddCompletionHandler.self],
       indentationWidth: indentationWidth