Add optional property to Identifier node

Summary:
Hermes currently parses optional function parameters (e.g. `function foo(a?) {}` or `(a?: string) => {}`), however it does not store whether a parameter is optional in the AST. Flow and Babel store this information as a boolean `optional` property on `Identifier` nodes which is `true` if the identifier is an optional function parameter, otherwise `optional` is false. Let's update Hermes' AST definition to now store an `optional` property on identifiers, just like Flow and Babel.

Almost all places where `IdentifierNodes` are created, optional is set to be false. In fact the only place where an `IdentifierNode` is directly created with `optional` set to true is within `parseBindingIdentifier` when we encounter a question mark directly following the identifier. There is only one other path through which optional identifiers are created: when reparsing arrow function parameters. To handle this case we also need to add an optional property to the `CoverTypedIdentifierNode`. Then when unwrapping a `CoverTypedIdentifierNode` in `reparseAssignmentPattern`, we pass the value of `optional` from the `CoverTypedIdentifierNode` to the `IdentifierNode`.

In addition, as per avp's suggestion we now allow declaring `ESTREE_IGNORE_IF_EMPTY` on boolean node properties. If the boolean is false, such as the new `optional` property for non-optional identifiers, then it will not be included in the JSON output. Without this we would have to update every single parser test that contains an identifier, instead of only the tests that contain optional parameters.

Reviewed By: avp

Differential Revision: D24210171

fbshipit-source-id: 2bb860ba2876d28100f17286bbb74e46dabf3cbc

include/hermes/AST/ESTree.def

@@ -372,16 +372,13 @@ ESTREE_NODE_3_ARGS(
 ESTREE_NODE_1_ARGS(Directive, Base, NodePtr, value, false)
 ESTREE_NODE_1_ARGS(DirectiveLiteral, Base, NodeLabel, value, false)
 
-ESTREE_NODE_2_ARGS(
-    Identifier,
-    Base,
-    NodeLabel,
-    name,
-    false,
-    NodePtr,
-    typeAnnotation,
-    true)
+ESTREE_NODE_3_ARGS(
+    Identifier, Base,
+    NodeLabel, name, false,
+    NodePtr, typeAnnotation, true,
+    NodeBoolean, optional, false)
 ESTREE_IGNORE_IF_EMPTY(Identifier, typeAnnotation)
+ESTREE_IGNORE_IF_EMPTY(Identifier, optional)
 
 ESTREE_NODE_2_ARGS(
     MetaProperty,
@@ -942,10 +939,11 @@ ESTREE_NODE_1_ARGS(
 // 'right' is the type which is either the cast target or the type annotation,
 //   which may be null if the identifier was simply given a '?' and no ':'
 //   with a type annotation.
-ESTREE_NODE_2_ARGS(
+ESTREE_NODE_3_ARGS(
     CoverTypedIdentifier, Cover,
     NodePtr, left, false,
-    NodePtr, right, true)
+    NodePtr, right, true,
+    NodeBoolean, optional, false)
 
 ESTREE_LAST(Cover)
 

lib/AST/CommonJS.cpp

@@ -21,11 +21,11 @@ ESTree::FunctionExpressionNode *wrapCJSModule(
 
   // Identifiers for function arguments.
   auto *exports = new (*context) ESTree::IdentifierNode(
-      context->getIdentifier("exports").getUnderlyingPointer(), nullptr);
+      context->getIdentifier("exports").getUnderlyingPointer(), nullptr, false);
   auto *require = new (*context) ESTree::IdentifierNode(
-      context->getIdentifier("require").getUnderlyingPointer(), nullptr);
+      context->getIdentifier("require").getUnderlyingPointer(), nullptr, false);
   auto *module = new (*context) ESTree::IdentifierNode(
-      context->getIdentifier("module").getUnderlyingPointer(), nullptr);
+      context->getIdentifier("module").getUnderlyingPointer(), nullptr, false);
   argNames.push_back(*exports);
   argNames.push_back(*require);
   argNames.push_back(*module);

lib/AST/ESTreeJSONDumper.cpp

@@ -133,7 +133,7 @@ class ESTreeJSONDumper {
   }
 
   static bool isEmpty(NodeBoolean val) {
-    return false;
+    return !val;
   }
 
   static bool isEmpty(NodeNumber num) {

lib/Parser/JSParserImpl-flow.cpp

@@ -129,7 +129,8 @@ Optional<ESTree::Node *> JSParserImpl::parseTypeAlias(
   ESTree::Node *id = setLocation(
       tok_,
       tok_,
-      new (context_) ESTree::IdentifierNode(tok_->getIdentifier(), nullptr));
+      new (context_)
+          ESTree::IdentifierNode(tok_->getIdentifier(), nullptr, false));
   SMLoc end = id->getEndLoc();
   advance(JSLexer::GrammarContext::Flow);
 
@@ -210,7 +211,8 @@ Optional<ESTree::Node *> JSParserImpl::parseInterfaceDeclaration(bool declare) {
   auto *id = setLocation(
       tok_,
       tok_,
-      new (context_) ESTree::IdentifierNode(tok_->getIdentifier(), nullptr));
+      new (context_)
+          ESTree::IdentifierNode(tok_->getIdentifier(), nullptr, false));
   advance(JSLexer::GrammarContext::Flow);
 
   ESTree::Node *typeParams = nullptr;
@@ -349,7 +351,7 @@ Optional<ESTree::Node *> JSParserImpl::parseDeclareFunction(SMLoc start) {
           new (context_) ESTree::FunctionTypeAnnotationNode(
               std::move(params), returnType, *optRest, typeParams))));
   auto *ident = setLocation(
-      idStart, func, new (context_) ESTree::IdentifierNode(id, func));
+      idStart, func, new (context_) ESTree::IdentifierNode(id, func, false));
   return setLocation(
       start,
       ident,
@@ -401,7 +403,8 @@ Optional<ESTree::Node *> JSParserImpl::parseDeclareModule(SMLoc start) {
     id = setLocation(
         tok_,
         tok_,
-        new (context_) ESTree::IdentifierNode(tok_->getIdentifier(), nullptr));
+        new (context_)
+            ESTree::IdentifierNode(tok_->getIdentifier(), nullptr, false));
   }
   advance(JSLexer::GrammarContext::Flow);
 
@@ -511,7 +514,8 @@ Optional<ESTree::Node *> JSParserImpl::parseDeclareClass(SMLoc start) {
   auto *id = setLocation(
       tok_,
       tok_,
-      new (context_) ESTree::IdentifierNode(tok_->getIdentifier(), nullptr));
+      new (context_)
+          ESTree::IdentifierNode(tok_->getIdentifier(), nullptr, false));
   advance(JSLexer::GrammarContext::Flow);
 
   ESTree::Node *typeParams = nullptr;
@@ -1463,8 +1467,8 @@ bool JSParserImpl::parsePropertyTypeAnnotation(
       ESTree::IdentifierNode *id = setLocation(
           tok_,
           tok_,
-          new (context_)
-              ESTree::IdentifierNode(tok_->getResWordOrIdentifier(), nullptr));
+          new (context_) ESTree::IdentifierNode(
+              tok_->getResWordOrIdentifier(), nullptr, false));
       advance(JSLexer::GrammarContext::Flow);
 
       if (!eat(
@@ -1552,7 +1556,7 @@ bool JSParserImpl::parsePropertyTypeAnnotation(
     key = setLocation(
         startRange,
         startRange,
-        new (context_) ESTree::IdentifierNode(staticIdent_, nullptr));
+        new (context_) ESTree::IdentifierNode(staticIdent_, nullptr, false));
     auto optProp = parseTypeProperty(start, variance, isStatic, key);
     if (!optProp)
       return false;
@@ -2023,8 +2027,8 @@ Optional<ESTree::GenericTypeAnnotationNode *> JSParserImpl::parseGenericType() {
   ESTree::Node *id = setLocation(
       tok_,
       tok_,
-      new (context_)
-          ESTree::IdentifierNode(tok_->getResWordOrIdentifier(), nullptr));
+      new (context_) ESTree::IdentifierNode(
+          tok_->getResWordOrIdentifier(), nullptr, false));
   advance(JSLexer::GrammarContext::Flow);
 
   while (checkAndEat(TokenKind::period, JSLexer::GrammarContext::Flow)) {
@@ -2039,8 +2043,8 @@ Optional<ESTree::GenericTypeAnnotationNode *> JSParserImpl::parseGenericType() {
     ESTree::Node *next = setLocation(
         tok_,
         tok_,
-        new (context_)
-            ESTree::IdentifierNode(tok_->getResWordOrIdentifier(), nullptr));
+        new (context_) ESTree::IdentifierNode(
+            tok_->getResWordOrIdentifier(), nullptr, false));
     advance(JSLexer::GrammarContext::Flow);
     id = setLocation(
         id, next, new (context_) ESTree::QualifiedTypeIdentifierNode(id, next));
@@ -2069,7 +2073,8 @@ Optional<ESTree::ClassImplementsNode *> JSParserImpl::parseClassImplements() {
   ESTree::Node *id = setLocation(
       tok_,
       tok_,
-      new (context_) ESTree::IdentifierNode(tok_->getIdentifier(), nullptr));
+      new (context_)
+          ESTree::IdentifierNode(tok_->getIdentifier(), nullptr, false));
   SMLoc end = advance(JSLexer::GrammarContext::Flow).End;
 
   ESTree::Node *typeParams = nullptr;
@@ -2137,7 +2142,7 @@ JSParserImpl::reparseTypeAnnotationAsIdentifier(ESTree::Node *typeAnnotation) {
   return setLocation(
       typeAnnotation,
       typeAnnotation,
-      new (context_) ESTree::IdentifierNode(id, nullptr));
+      new (context_) ESTree::IdentifierNode(id, nullptr, false));
 }
 
 Optional<ESTree::Node *> JSParserImpl::parseEnumDeclaration() {
@@ -2314,7 +2319,8 @@ Optional<ESTree::Node *> JSParserImpl::parseEnumMember() {
   ESTree::Node *id = setLocation(
       tok_,
       tok_,
-      new (context_) ESTree::IdentifierNode(tok_->getIdentifier(), nullptr));
+      new (context_)
+          ESTree::IdentifierNode(tok_->getIdentifier(), nullptr, false));
   advance();
 
   ESTree::Node *member = nullptr;