Update code gen formatting

Author: kimdv

CodeGeneration/Sources/Utils/CodeGenerationFormat.swift

@@ -42,4 +42,71 @@ public class CodeGenerationFormat: BasicFormat {
       return super.visit(node)
     }
   }
+
+  public override func visit(_ node: TupleExprElementListSyntax) -> TupleExprElementListSyntax {
+    let children = node.children(viewMode: .all)
+    // If the function only takes a single argument, display it on the same line
+    if let callee = node.parent?.as(FunctionCallExprSyntax.self)?.calledExpression.as(MemberAccessExprSyntax.self), callee.base == nil {
+      // This is a constructor for tokens. Write them on a single line
+      return super.visit(node)
+    }
+    if children.count > 3 {
+      return TupleExprElementListSyntax(formatChildrenSeparatedByNewline(children: children, elementType: TupleExprElementSyntax.self))
+    } else {
+      return super.visit(node)
+    }
+  }
+
+  public override func visit(_ node: FunctionParameterListSyntax) -> FunctionParameterListSyntax {
+    let children = node.children(viewMode: .all)
+    // Short array literals are presented on one line, list each element on a different line.
+    if children.count > 3 {
+      return FunctionParameterListSyntax(formatChildrenSeparatedByNewline(children: children, elementType: FunctionParameterSyntax.self))
+    } else {
+      return super.visit(node)
+    }
+  }
+
+  public override func visit(_ node: ArrayElementListSyntax) -> ArrayElementListSyntax {
+    let children = node.children(viewMode: .all)
+    // Short array literals are presented on one line, list each element on a different line.
+    if children.count > 2 {
+      return ArrayElementListSyntax(formatChildrenSeparatedByNewline(children: children, elementType: ArrayElementSyntax.self))
+    } else {
+      return super.visit(node)
+    }
+  }
+
+  public override func visit(_ node: DictionaryElementListSyntax) -> DictionaryElementListSyntax {
+    let children = node.children(viewMode: .all)
+    // Short array literals are presented on one line, list each element on a different line.
+    if children.count > 2 {
+      return DictionaryElementListSyntax(formatChildrenSeparatedByNewline(children: children, elementType: DictionaryElementSyntax.self))
+    } else {
+      return super.visit(node)
+    }
+  }
+}
+
+// MARK: - Private helpers
+
+fileprivate extension CodeGenerationFormat {
+  func formatChildrenSeparatedByNewline<SyntaxType: SyntaxProtocol>(children: SyntaxChildren, elementType: SyntaxType.Type) -> [SyntaxType] {
+    indentationLevel += 1
+    var formattedChildren = children.map {
+      self.visit($0).as(SyntaxType.self)!
+    }
+    formattedChildren = formattedChildren.map {
+      if $0.leadingTrivia?.first?.isNewline == true {
+        return $0
+      } else {
+        return $0.with(\.leadingTrivia, indentedNewline + ($0.leadingTrivia ?? []))
+      }
+    }
+    indentationLevel -= 1
+    if !formattedChildren.isEmpty {
+      formattedChildren[formattedChildren.count - 1] = formattedChildren[formattedChildren.count - 1].with(\.trailingTrivia, indentedNewline)
+    }
+    return formattedChildren
+  }
 }

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

@@ -17,7 +17,7 @@ import Utils
 
 let lookupTable = ArrayExprSyntax(leftSquare: .leftSquareBracketToken(trailingTrivia: .newline)) {
   for keyword in KEYWORDS {
-    ArrayElementSyntax(expression: ExprSyntax("\(literal: keyword.name)"), trailingComma: .commaToken(), trailingTrivia: .newline)
+    ArrayElementSyntax(expression: ExprSyntax("\(literal: keyword.name)"), trailingComma: .commaToken())
   }
 }
 

Sources/SwiftBasicFormat/generated/BasicFormat.swift

@@ -61,10 +61,11 @@ open class BasicFormat: SyntaxRewriter {
     leadingTrivia = leadingTrivia.indented(indentation: indentation)
     trailingTrivia = trailingTrivia.indented(indentation: indentation)
     let rewritten = TokenSyntax(
-      node.tokenKind, 
-      leadingTrivia: leadingTrivia, 
-      trailingTrivia: trailingTrivia, 
-      presence: node.presence
+        node.tokenKind, 
+        leadingTrivia: leadingTrivia, 
+        trailingTrivia: trailingTrivia, 
+        presence: node.presence
+      
     )
     lastRewrittenToken = rewritten
     putNextTokenOnNewLine = false