update node creator codegen to better handle optional props

Summary:
previously the codegen would emit something like `DetachedNode<null | Identifier>` for an optional property - which technically correct, but pretty hard to use.
This just updates the codegen to mark optional properties as optional so that they can be omitted or set to an explicit `null`.

Reviewed By: pieterv

Differential Revision: D32269199

fbshipit-source-id: 24517ed25925fac2b140b837aa822c8b6e1a76df

tools/hermes-parser/js/hermes-transform/src/generated/node-types.js

@@ -48,17 +48,15 @@ export function BlockStatement({
 
 export function ExpressionStatement({
   parent,
-  expression,
-  directive = null,
+  ...props
 }: {
   +expression: DetachedNode<ExpressionStatementType['expression']>,
-  +directive?: ExpressionStatementType['directive'],
+  +directive?: ?ExpressionStatementType['directive'],
   +parent?: ESNode,
 }): DetachedNode<ExpressionStatementType> {
   const node = detachedProps<ExpressionStatementType>(parent, {
     type: 'ExpressionStatement',
-    expression,
-    directive,
+    ...props,
   });
   setParentPointersInDirectChildren(node);
   return node;
@@ -96,7 +94,7 @@ export function VariableDeclarator({
   parent,
   ...props
 }: {
-  +init: DetachedNode<VariableDeclaratorType['init']>,
+  +init?: ?DetachedNode<VariableDeclaratorType['init']>,
   +id: DetachedNode<VariableDeclaratorType['id']>,
   +parent?: ESNode,
 }): DetachedNode<VariableDeclaratorType> {

tools/hermes-parser/js/hermes-transform/src/generated/special-case-node-types.js

@@ -19,7 +19,6 @@ import type {
   RegExpLiteral as RegExpLiteralType,
   TemplateElement as TemplateElementType,
   Identifier as IdentifierType,
-  ExpressionStatement as ExpressionStatementType,
   BooleanLiteral as BooleanLiteralType,
   NumericLiteral as NumericLiteralType,
   NullLiteral as NullLiteralType,
@@ -96,26 +95,6 @@ export function Identifier({
   return node;
 }
 
-// hermes always emits the directive prop, but nobody should ever want to use it
-// so we default it to `null` here
-export function ExpressionStatement({
-  parent,
-  expression,
-  directive = null,
-}: {
-  +expression: DetachedNode<ExpressionStatementType['expression']>,
-  +directive?: ExpressionStatementType['directive'],
-  +parent?: ESNode,
-}): DetachedNode<ExpressionStatementType> {
-  const node = detachedProps<ExpressionStatementType>(parent, {
-    type: 'ExpressionStatement',
-    expression,
-    directive,
-  });
-  setParentPointersInDirectChildren(node);
-  return node;
-}
-
 //
 // Literals require a "raw" which is added by the estree transform, not hermes.
 //

tools/hermes-parser/js/scripts/genTransformNodeTypes.js

@@ -21,7 +21,6 @@ const NODES_WITH_SPECIAL_HANDLING = new Set([
   'RegExpLiteral',
   'TemplateElement',
   'Identifier',
-  'ExpressionStatement',
   'BooleanLiteral',
   'NumericLiteral',
   'NullLiteral',
@@ -70,6 +69,10 @@ export function ${node.name}({parent, ...props}: {
       } else if (arg.type === 'NodeList') {
         type = `$ReadOnlyArray<DetachedNode<${type}[number]>>`;
       }
+
+      if (arg.optional) {
+        return `+${arg.name}?: ?${type}`;
+      }
       return `+${arg.name}: ${type}`;
     })
     .join(',\n')},