Include property names in debug description

Author: ahoppen

CodeGeneration/Sources/generate-swiftsyntax/GenerateSwiftSyntax.swift

@@ -98,6 +98,7 @@ struct GenerateSwiftSyntax: ParsableCommand {
         GeneratedFileSpec(swiftParserDiagnosticsGeneratedDir + ["TokenNameForDiagnostics.swift"], tokenNameForDiagnosticFile),
 
         // SwiftSyntax
+        GeneratedFileSpec(swiftSyntaxGeneratedDir + ["ChildNameForKeyPath.swift"], childNameForKeyPathFile),
         GeneratedFileSpec(swiftSyntaxGeneratedDir + ["Keyword.swift"], keywordFile),
         GeneratedFileSpec(swiftSyntaxGeneratedDir + ["raw", "RawSyntaxNodes.swift"], rawSyntaxNodesFile),
         GeneratedFileSpec(swiftSyntaxGeneratedDir + ["raw", "RawSyntaxValidation.swift"], rawSyntaxValidationFile),

CodeGeneration/Sources/generate-swiftsyntax/templates/swiftsyntax/ChildNameForKeyPathFile.swift

@@ -0,0 +1,45 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+import SwiftSyntaxBuilder
+import SyntaxSupport
+import Utils
+
+let childNameForKeyPathFile = SourceFileSyntax(leadingTrivia: copyrightHeader) {
+  try! FunctionDeclSyntax(
+    """
+    /// If the keyPath is one from a layout structure, return the property name
+    /// of it.
+    internal func childName(_ keyPath: AnyKeyPath) -> String?
+    """
+  ) {
+    try! SwitchExprSyntax("switch keyPath") {
+      for node in NON_BASE_SYNTAX_NODES where !node.isSyntaxCollection {
+        for child in node.children {
+          SwitchCaseSyntax(
+            """
+            case \\\(raw: node.type.syntaxBaseName).\(raw: child.swiftName):
+              return \(literal: child.swiftName)
+            """
+          )
+        }
+      }
+      SwitchCaseSyntax(
+        """
+        default:
+          return nil
+        """
+      )
+    }
+  }
+}

Sources/SwiftSyntax/CMakeLists.txt

@@ -34,6 +34,7 @@ add_swift_host_library(SwiftSyntax
   generated/raw/RawSyntaxNodes.swift
   generated/raw/RawSyntaxValidation.swift
 
+  generated/ChildNameForKeyPath.swift
   generated/Keyword.swift
   generated/SyntaxAnyVisitor.swift
   generated/SyntaxBaseNodes.swift

Sources/SwiftSyntax/Syntax.swift

@@ -635,6 +635,11 @@ public extension SyntaxProtocol {
       target.write("\n")
       target.write(indentString)
       target.write(isLastChild ? "╰─" : "├─")
+      if let keyPath = child.keyPathInParent, let name = childName(keyPath) {
+        target.write("\(name): ")
+      } else if self.kind.isSyntaxCollection {
+        target.write("[\(num)]: ")
+      }
       let childIndentString = indentString + (isLastChild ? "  " : "│ ")
       child.debugWrite(
         to: &target,