Use local git package for code gen

CodeGeneration/Package.swift

@@ -1,6 +1,7 @@
 // swift-tools-version:5.7
 
 import PackageDescription
+import Foundation
 
 let package = Package(
   name: "CodeGeneration",
@@ -11,8 +12,7 @@ let package = Package(
     .executable(name: "generate-swiftsyntax", targets: ["generate-swiftsyntax"])
   ],
   dependencies: [
-    .package(url: "https://github.com/apple/swift-syntax.git", revision: "c7087adb193b26f02b59d21cd06d17ec202d1bf5"),
-    .package(url: "https://github.com/apple/swift-argument-parser.git", from: "1.2.2"),
+    .package(url: "..", revision: "HEAD")
   ],
   targets: [
     .executableTarget(
@@ -41,3 +41,14 @@ let package = Package(
     ),
   ]
 )
+
+if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
+  // Building standalone.
+  package.dependencies += [
+    .package(url: "https://github.com/apple/swift-argument-parser.git", from: "1.2.2")
+  ]
+} else {
+  package.dependencies += [
+    .package(path: "../../swift-argument-parser")
+  ]
+}

CodeGeneration/README.md

@@ -4,7 +4,8 @@ This directory contains file to generate source code that is part of the SwiftSy
 
 Some source code inside SwiftSyntax is generated using [SwiftSyntaxBuilder](../Sources/SwiftSyntaxBuilder), a Swift library whose purpose is to generate Swift code using Swift itself. This kind of code generation is performed by the Swift package defined in this directory.
 
-This directory is a standalone package that uses a pinned version of SwiftSyntaxBuilder. It is thus NOT using SwiftSyntaxBuilder of the parent directory. This guarantees that when `generate-swiftsyntax` is run, it can't break its own build.
+This directory is a standalone package that uses HEAD of the current branch. This guarantees that when `generate-swiftsyntax` is run, it can't break its own build when run multiple times without committing. 
+This means that `CodeGeneration` will build against your latest local commit of SwiftSyntax. If you are making changes to `SwiftSyntax` that affect how code is being generated, commit your SwiftSyntax changes (pushing is not necessary) and re-generate files afterwards.
 
 To re-generate the files after changing `CodeGeneration` run the `generate-swiftsyntax` 
 target of `CodeGeneration` and pass `path/to/swift-syntax/Sources` as the argument.

Sources/SwiftSyntax/generated/SyntaxRewriter.swift

@@ -6904,8 +6904,8 @@ open class SyntaxRewriter {
     var childIndex = 0
     for (raw, info) in RawSyntaxChildren(syntaxNode) {
       defer {
-          childIndex += 1
-        }
+        childIndex += 1
+      }
       guard let child = raw else {
         // Node does not exist. If we are collecting rewritten nodes, we need to
         // collect this one as well, otherwise we can ignore it.