Workaround new trivia behavior in SwiftSyntax.

Sources/SwiftFormat/Parsing.swift

@@ -12,6 +12,7 @@
 
 import Foundation
 import SwiftDiagnostics
+import SwiftFormatCore
 import SwiftOperators
 import SwiftParser
 import SwiftSyntax
@@ -54,5 +55,5 @@ func parseAndEmitDiagnostics(
     throw SwiftFormatError.fileContainsInvalidSyntax
   }
 
-  return sourceFile
+  return restoringLegacyTriviaBehavior(sourceFile)
 }

Sources/SwiftFormatCore/LegacyTriviaBehavior.swift

@@ -0,0 +1,44 @@
+import SwiftSyntax
+
+/// Rewrites the trivia on tokens in the given source file to restore the legacy trivia behavior
+/// before https://github.com/apple/swift-syntax/pull/985 was merged.
+///
+/// Eventually we should get rid of this and update the core formatting code to adjust to the new
+/// behavior, but this workaround lets us keep the current implementation without larger changes.
+public func restoringLegacyTriviaBehavior(_ sourceFile: SourceFileSyntax) -> SourceFileSyntax {
+  return LegacyTriviaBehaviorRewriter().visit(sourceFile).as(SourceFileSyntax.self)!
+}
+
+private final class LegacyTriviaBehaviorRewriter: SyntaxRewriter {
+  /// Trivia that was extracted from the trailing trivia of a token to be prepended to the leading
+  /// trivia of the next token.
+  private var pendingLeadingTrivia: Trivia?
+
+  override func visit(_ token: TokenSyntax) -> TokenSyntax {
+    var token = token
+    if let pendingLeadingTrivia = pendingLeadingTrivia {
+      token = token.withLeadingTrivia(pendingLeadingTrivia + token.leadingTrivia)
+      self.pendingLeadingTrivia = nil
+    }
+    if token.nextToken != nil,
+      let firstIndexToMove = token.trailingTrivia.firstIndex(where: shouldTriviaPieceBeMoved)
+    {
+      pendingLeadingTrivia = Trivia(pieces: Array(token.trailingTrivia[firstIndexToMove...]))
+      token =
+        token.withTrailingTrivia(Trivia(pieces: Array(token.trailingTrivia[..<firstIndexToMove])))
+    }
+    return token
+  }
+}
+
+/// Returns a value indicating whether the given trivia piece should be moved from a token's
+/// trailing trivia to the leading trivia of the following token to restore the legacy trivia
+/// behavior.
+private func shouldTriviaPieceBeMoved(_ piece: TriviaPiece) -> Bool {
+  switch piece {
+  case .spaces, .tabs, .unexpectedText:
+    return false
+  default:
+    return true
+  }
+}

Sources/SwiftFormatPrettyPrint/TokenStreamCreator.swift

@@ -1249,6 +1249,15 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
     return .visitChildren
   }
 
+  override func visit(_ node: MacroExpansionExprSyntax) -> SyntaxVisitorContinueKind {
+    arrangeFunctionCallArgumentList(
+      node.argumentList,
+      leftDelimiter: node.leftParen,
+      rightDelimiter: node.rightParen,
+      forcesBreakBeforeRightDelimiter: false)
+    return .visitChildren
+  }
+
   override func visit(_ node: ParameterClauseSyntax) -> SyntaxVisitorContinueKind {
     // Prioritize keeping ") throws -> <return_type>" together. We can only do this if the function
     // has arguments.
@@ -3595,11 +3604,11 @@ class CommentMovingRewriter: SyntaxRewriter {
     return super.visit(node)
   }
 
-  override func visit(_ token: TokenSyntax) -> Syntax {
+  override func visit(_ token: TokenSyntax) -> TokenSyntax {
     if let rewrittenTrivia = rewriteTokenTriviaMap[token] {
-      return Syntax(token.withLeadingTrivia(rewrittenTrivia))
+      return token.withLeadingTrivia(rewrittenTrivia)
     }
-    return Syntax(token)
+    return token
   }
 
   override func visit(_ node: InfixOperatorExprSyntax) -> ExprSyntax {

Sources/SwiftFormatRules/ReplaceTrivia.swift

@@ -26,11 +26,11 @@ fileprivate final class ReplaceTrivia: SyntaxRewriter {
     self.trailingTrivia = trailingTrivia
   }
 
-  override func visit(_ token: TokenSyntax) -> Syntax {
-    guard token == self.token else { return Syntax(token) }
-    let newNode = token.withLeadingTrivia(leadingTrivia ?? token.leadingTrivia)
+  override func visit(_ token: TokenSyntax) -> TokenSyntax {
+    guard token == self.token else { return token }
+    return token
+      .withLeadingTrivia(leadingTrivia ?? token.leadingTrivia)
       .withTrailingTrivia(trailingTrivia ?? token.trailingTrivia)
-    return Syntax(newNode)
   }
 }
 

Tests/SwiftFormatPrettyPrintTests/PrettyPrintTestCase.swift

@@ -67,8 +67,9 @@ class PrettyPrintTestCase: DiagnosingTestCase {
   ) -> String? {
     // Ignore folding errors for unrecognized operators so that we fallback to a reasonable default.
     let sourceFileSyntax =
-      OperatorTable.standardOperators.foldAll(Parser.parse(source: source)) { _ in }
-        .as(SourceFileSyntax.self)!
+      restoringLegacyTriviaBehavior(
+        OperatorTable.standardOperators.foldAll(Parser.parse(source: source)) { _ in }
+          .as(SourceFileSyntax.self)!)
     let context = makeContext(sourceFileSyntax: sourceFileSyntax, configuration: configuration)
     let printer = PrettyPrinter(
       context: context,

Tests/SwiftFormatRulesTests/LintOrFormatRuleTestCase.swift

@@ -19,7 +19,7 @@ class LintOrFormatRuleTestCase: DiagnosingTestCase {
     file: StaticString = #file,
     line: UInt = #line
   ) {
-    let sourceFileSyntax = Parser.parse(source: input)
+    let sourceFileSyntax = restoringLegacyTriviaBehavior(Parser.parse(source: input))
 
     // Force the rule to be enabled while we test it.
     var configuration = Configuration()
@@ -56,7 +56,7 @@ class LintOrFormatRuleTestCase: DiagnosingTestCase {
     file: StaticString = #file,
     line: UInt = #line
   ) {
-    let sourceFileSyntax = Parser.parse(source: input)
+    let sourceFileSyntax = restoringLegacyTriviaBehavior(Parser.parse(source: input))
 
     // Force the rule to be enabled while we test it.
     var configuration = configuration ?? Configuration()