Respect indentation in the line for sub tree in BasicFormat

Author: gibachan

Sources/SwiftBasicFormat/BasicFormat.swift

@@ -413,6 +413,15 @@ open class BasicFormat: SyntaxRewriter {
       anchorPoints[token] = currentIndentationLevel
     }
 
+    // Add an indentation in the line for the initial token,
+    // if the token is present and its leadingTrivia does not contain the indentation.
+    if isInitialToken && token.presence == .present {
+      let indentationOfLine = token.indentationOfLine
+      if token.leadingTrivia.pieces.suffix(indentationOfLine.pieces.count) != indentationOfLine.pieces {
+        leadingTrivia += token.indentationOfLine
+      }
+    }
+
     // Add a trailing space to the token unless
     //  - it already ends with a whitespace or
     //  - the next token will start starts with a newline after the rewrite

Sources/SwiftBasicFormat/Syntax+Extensions.swift

@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+
+public extension TokenSyntax {
+  /// The indentation of this token
+  ///
+  /// In contrast to `indentation`, this does not walk to previous tokens to
+  /// find the indentation of the line this token occurs on.
+  private var indentation: Trivia? {
+    let previous = self.previousToken(viewMode: .sourceAccurate)
+    return ((previous?.trailingTrivia ?? []) + leadingTrivia).indentation(isOnNewline: false)
+  }
+
+  /// Returns the indentation of the line this token occurs on
+  var indentationOfLine: Trivia {
+    var token: TokenSyntax = self
+    if let indentation = token.indentation {
+      return indentation
+    }
+    while let previous = token.previousToken(viewMode: .sourceAccurate) {
+      token = previous
+      if let indentation = token.indentation {
+        return indentation
+      }
+    }
+
+    return []
+  }
+}

Sources/SwiftParserDiagnostics/MissingNodesError.swift

@@ -36,7 +36,11 @@ fileprivate enum NodesDescriptionPart {
     switch self {
     case .tokensWithDefaultText(var tokens):
       if format {
-        tokens = tokens.map({ NoNewlinesFormat(viewMode: .all).visit($0) })
+        tokens = tokens.enumerated()
+          .map { index, token in
+            // We detach the nodes from the second one onwards, considering the line indentation only for the first node
+            NoNewlinesFormat(viewMode: .all).visit(index == 0 ? token : token.detached)
+          }
       }
       if !tokens.isEmpty {
         tokens[0] = tokens[0].with(\.leadingTrivia, [])

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -51,31 +51,6 @@ fileprivate func getTokens(between first: TokenSyntax, and second: TokenSyntax)
 }
 
 fileprivate extension TokenSyntax {
-  /// The indentation of this token
-  ///
-  /// In contrast to `indentation`, this does not walk to previous tokens to
-  /// find the indentation of the line this token occurs on.
-  private var indentation: Trivia? {
-    let previous = self.previousToken(viewMode: .sourceAccurate)
-    return ((previous?.trailingTrivia ?? []) + leadingTrivia).indentation(isOnNewline: false)
-  }
-
-  /// Returns the indentation of the line this token occurs on
-  var indentationOfLine: Trivia {
-    var token: TokenSyntax = self
-    if let indentation = token.indentation {
-      return indentation
-    }
-    while let previous = token.previousToken(viewMode: .sourceAccurate) {
-      token = previous
-      if let indentation = token.indentation {
-        return indentation
-      }
-    }
-
-    return []
-  }
-
   /// Assuming this token is a `poundAvailableKeyword` or `poundUnavailableKeyword`
   /// returns the opposite keyword.
   var negatedAvailabilityKeyword: TokenSyntax {

Tests/SwiftBasicFormatTest/BasicFormatTests.swift

@@ -374,7 +374,7 @@ final class BasicFormatTest: XCTestCase {
     assertFormatted(
       tree: body,
       expected: """
-        {
+            {
                 print(1)
             }
         """