ES2020 optimizations

.eslintrc.yml

@@ -561,7 +561,7 @@ overrides:
       '@typescript-eslint/parameter-properties': error
       '@typescript-eslint/prefer-as-const': error
       '@typescript-eslint/prefer-enum-initializers': error
-      '@typescript-eslint/prefer-for-of': error
+      '@typescript-eslint/prefer-for-of': off
       '@typescript-eslint/prefer-function-type': error
       '@typescript-eslint/prefer-includes': error
       '@typescript-eslint/prefer-literal-enum-member': error

src/execution/collectFields.ts

@@ -70,7 +70,8 @@ export function collectSubfields(
 ): Map<string, ReadonlyArray<FieldNode>> {
   const subFieldNodes = new AccumulatorMap<string, FieldNode>();
   const visitedFragmentNames = new Set<string>();
-  for (const node of fieldNodes) {
+  for (let i = 0; i < fieldNodes.length; i++) {
+    const node = fieldNodes[i];
     if (node.selectionSet) {
       collectFieldsImpl(
         schema,
@@ -96,7 +97,8 @@ function collectFieldsImpl(
   fields: AccumulatorMap<string, FieldNode>,
   visitedFragmentNames: Set<string>,
 ): void {
-  for (const selection of selectionSet.selections) {
+  for (let i = 0; i < selectionSet.selections.length; i++) {
+    const selection = selectionSet.selections[i];
     switch (selection.kind) {
       case Kind.FIELD: {
         if (!shouldIncludeNode(variableValues, selection)) {

src/execution/execute.ts

@@ -265,7 +265,8 @@ export function buildExecutionContext(
 
   let operation: OperationDefinitionNode | undefined;
   const fragments: ObjMap<FragmentDefinitionNode> = Object.create(null);
-  for (const definition of document.definitions) {
+  for (let i = 0; i < document.definitions.length; i++) {
+    const definition = document.definitions[i];
     switch (definition.kind) {
       case Kind.OPERATION_DEFINITION:
         if (operationName == null) {
@@ -431,7 +432,9 @@ function executeFields(
   const results = Object.create(null);
   let containsPromise = false;
 
-  for (const [responseName, fieldNodes] of fields.entries()) {
+  const fieldsEntries = Array.from(fields.entries());
+  for (let i = 0; i < fieldsEntries.length; i++) {
+    const { 0: responseName, 1: fieldNodes } = fieldsEntries[i];
     const fieldPath = addPath(path, responseName, parentType.name);
     const result = executeField(
       exeContext,
@@ -1227,7 +1230,9 @@ function executeSubscription(
     rootType,
     operation.selectionSet,
   );
-  const [responseName, fieldNodes] = [...rootFields.entries()][0];
+  const { 0: responseName, 1: fieldNodes } = Array.from(
+    rootFields.entries(),
+  )[0];
   const fieldName = fieldNodes[0].name.value;
   const fieldDef = schema.getField(rootType, fieldName);
 

src/execution/values.ts

@@ -76,7 +76,8 @@ function coerceVariableValues(
   onError: (error: GraphQLError) => void,
 ): { [variable: string]: unknown } {
   const coercedValues: { [variable: string]: unknown } = {};
-  for (const varDefNode of varDefNodes) {
+  for (let i = 0; i < varDefNodes.length; i++) {
+    const varDefNode = varDefNodes[i];
     const varName = varDefNode.variable.name.value;
     const varType = typeFromAST(schema, varDefNode.type);
     if (!isInputType(varType)) {
@@ -161,7 +162,8 @@ export function getArgumentValues(
   const argumentNodes = node.arguments ?? [];
   const argNodeMap = keyMap(argumentNodes, (arg) => arg.name.value);
 
-  for (const argDef of def.args) {
+  for (let i = 0; i < def.args.length; i++) {
+    const argDef = def.args[i];
     const name = argDef.name;
     const argType = argDef.type;
     const argumentNode = argNodeMap[name];

src/jsutils/groupBy.ts

@@ -8,7 +8,8 @@ export function groupBy<K, T>(
   keyFn: (item: T) => K,
 ): Map<K, ReadonlyArray<T>> {
   const result = new AccumulatorMap<K, T>();
-  for (const item of list) {
+  for (let i = 0; i < list.length; i++) {
+    const item = list[i];
     result.add(keyFn(item), item);
   }
   return result;

src/jsutils/keyMap.ts

@@ -32,8 +32,9 @@ export function keyMap<T>(
   keyFn: (item: T) => string,
 ): ObjMap<T> {
   const result = Object.create(null);
-  for (const item of list) {
-    result[keyFn(item)] = item;
+  for (let i = 0; i < list.length; i++) {
+    const key = list[i];
+    result[keyFn(key)] = key;
   }
   return result;
 }

src/jsutils/keyValMap.ts

@@ -23,7 +23,8 @@ export function keyValMap<T, V>(
   valFn: (item: T) => V,
 ): ObjMap<V> {
   const result = Object.create(null);
-  for (const item of list) {
+  for (let i = 0; i < list.length; i++) {
+    const item = list[i];
     result[keyFn(item)] = valFn(item);
   }
   return result;

src/jsutils/mapValue.ts

@@ -9,8 +9,9 @@ export function mapValue<T, V>(
   fn: (value: T, key: string) => V,
 ): ObjMap<V> {
   const result = Object.create(null);
-
-  for (const key of Object.keys(map)) {
+  const keys = Object.keys(map);
+  for (let i = 0; i < keys.length; i++) {
+    const key = keys[i];
     result[key] = fn(map[key], key);
   }
   return result;

src/jsutils/promiseForObject.ts

@@ -12,7 +12,7 @@ export function promiseForObject<T>(
 ): Promise<ObjMap<T>> {
   return Promise.all(Object.values(object)).then((resolvedValues) => {
     const resolvedObject = Object.create(null);
-    for (const [i, key] of Object.keys(object).entries()) {
+    for (const { 0: i, 1: key } of Object.keys(object).entries()) {
       resolvedObject[key] = resolvedValues[i];
     }
     return resolvedObject;

src/jsutils/toObjMap.ts

@@ -13,7 +13,9 @@ export function toObjMap<T>(
   }
 
   const map = Object.create(null);
-  for (const [key, value] of Object.entries(obj)) {
+  const entries = Object.entries(obj);
+  for (let i = 0; i < entries.length; i++) {
+    const { 0: key, 1: value } = entries[i];
     map[key] = value;
   }
   return map;

src/language/visitor.ts

@@ -85,6 +85,7 @@ export type ASTVisitorKeyMap = {
 };
 
 export const BREAK: unknown = Object.freeze({});
+const KINDS = Object.values(Kind);
 
 /**
  * visit() will walk through an AST using a depth-first traversal, calling
@@ -180,7 +181,8 @@ export function visit(
   visitorKeys: ASTVisitorKeyMap = QueryDocumentKeys,
 ): any {
   const enterLeaveMap = new Map<Kind, EnterLeaveVisitor<ASTNode>>();
-  for (const kind of Object.values(Kind)) {
+  for (let i = 0; i < KINDS.length; i++) {
+    const kind = KINDS[i];
     enterLeaveMap.set(kind, getEnterLeaveForKind(visitor, kind));
   }
 
@@ -210,7 +212,8 @@ export function visit(
           node = node.slice();
 
           let editOffset = 0;
-          for (const [editKey, editValue] of edits) {
+          for (let i = 0; i < edits.length; i++) {
+            const { 0: editKey, 1: editValue } = edits[i];
             const arrayKey = editKey - editOffset;
             if (editValue === null) {
               node.splice(arrayKey, 1);
@@ -224,7 +227,8 @@ export function visit(
             {},
             Object.getOwnPropertyDescriptors(node),
           );
-          for (const [editKey, editValue] of edits) {
+          for (let i = 0; i < edits.length; i++) {
+            const { 0: editKey, 1: editValue } = edits[i];
             node[editKey] = editValue;
           }
         }
@@ -314,7 +318,8 @@ export function visitInParallel(
   const skipping = new Array(visitors.length).fill(null);
   const mergedVisitor = Object.create(null);
 
-  for (const kind of Object.values(Kind)) {
+  for (let j = 0; j < KINDS.length; j++) {
+    const kind = KINDS[j];
     let hasVisitor = false;
     const enterList = new Array(visitors.length).fill(undefined);
     const leaveList = new Array(visitors.length).fill(undefined);

src/type/schema.ts

@@ -172,7 +172,8 @@ export class GraphQLSchema {
     // the set of "collected" types, so `collectReferencedTypes` ignore them.
     const allReferencedTypes = new Set<GraphQLNamedType>(config.types);
     if (config.types != null) {
-      for (const type of config.types) {
+      for (let i = 0; i < config.types.length; i++) {
+        const type = config.types[i];
         // When we ready to process this type, we remove it from "collected" types
         // and then add it together with all dependent types in the correct position.
         allReferencedTypes.delete(type);
@@ -190,10 +191,12 @@ export class GraphQLSchema {
       collectReferencedTypes(this._subscriptionType, allReferencedTypes);
     }
 
-    for (const directive of this._directives) {
+    for (let i = 0; i < this._directives.length; i++) {
+      const directive = this._directives[i];
       // Directives are not validated until validateSchema() is called.
       if (isDirective(directive)) {
-        for (const arg of directive.args) {
+        for (let j = 0; j < directive.args.length; j++) {
+          const arg = directive.args[j];
           collectReferencedTypes(arg.type, allReferencedTypes);
         }
       }
@@ -206,7 +209,9 @@ export class GraphQLSchema {
     // Keep track of all implementations by interface name.
     this._implementationsMap = Object.create(null);
 
-    for (const namedType of allReferencedTypes) {
+    const refTypes = Array.from(allReferencedTypes);
+    for (let j = 0; j < refTypes.length; j++) {
+      const namedType = refTypes[j];
       if (namedType == null) {
         continue;
       }
@@ -221,7 +226,9 @@ export class GraphQLSchema {
 
       if (isInterfaceType(namedType)) {
         // Store implementations by interface.
-        for (const iface of namedType.getInterfaces()) {
+        const interfaces = namedType.getInterfaces();
+        for (let i = 0; i < interfaces.length; i++) {
+          const iface = interfaces[i];
           if (isInterfaceType(iface)) {
             let implementations = this._implementationsMap[iface.name];
             if (implementations === undefined) {
@@ -236,7 +243,9 @@ export class GraphQLSchema {
         }
       } else if (isObjectType(namedType)) {
         // Store implementations by objects.
-        for (const iface of namedType.getInterfaces()) {
+        const interfaces = namedType.getInterfaces();
+        for (let i = 0; i < interfaces.length; i++) {
+          const iface = interfaces[i];
           if (isInterfaceType(iface)) {
             let implementations = this._implementationsMap[iface.name];
             if (implementations === undefined) {
@@ -313,16 +322,17 @@ export class GraphQLSchema {
       map = Object.create(null);
 
       if (isUnionType(abstractType)) {
-        for (const type of abstractType.getTypes()) {
-          map[type.name] = true;
+        const types = abstractType.getTypes();
+        for (let i = 0; i < types.length; i++) {
+          map[types[i].name] = true;
         }
       } else {
         const implementations = this.getImplementations(abstractType);
-        for (const type of implementations.objects) {
-          map[type.name] = true;
+        for (let i = 0; i < implementations.objects.length; i++) {
+          map[implementations.objects[i].name] = true;
         }
-        for (const type of implementations.interfaces) {
-          map[type.name] = true;
+        for (let i = 0; i < implementations.interfaces.length; i++) {
+          map[implementations.interfaces[i].name] = true;
         }
       }
 
@@ -437,23 +447,28 @@ function collectReferencedTypes(
   if (!typeSet.has(namedType)) {
     typeSet.add(namedType);
     if (isUnionType(namedType)) {
-      for (const memberType of namedType.getTypes()) {
-        collectReferencedTypes(memberType, typeSet);
+      const types = namedType.getTypes();
+      for (let i = 0; i < types.length; i++) {
+        collectReferencedTypes(types[i], typeSet);
       }
     } else if (isObjectType(namedType) || isInterfaceType(namedType)) {
-      for (const interfaceType of namedType.getInterfaces()) {
-        collectReferencedTypes(interfaceType, typeSet);
+      const interfaces = namedType.getInterfaces();
+      for (let i = 0; i < interfaces.length; i++) {
+        collectReferencedTypes(interfaces[i], typeSet);
       }
 
-      for (const field of Object.values(namedType.getFields())) {
+      const fields = Object.values(namedType.getFields());
+      for (let i = 0; i < fields.length; i++) {
+        const field = fields[i];
         collectReferencedTypes(field.type, typeSet);
-        for (const arg of field.args) {
-          collectReferencedTypes(arg.type, typeSet);
+        for (let j = 0; j < field.args.length; j++) {
+          collectReferencedTypes(field.args[j].type, typeSet);
         }
       }
     } else if (isInputObjectType(namedType)) {
-      for (const field of Object.values(namedType.getFields())) {
-        collectReferencedTypes(field.type, typeSet);
+      const fields = Object.values(namedType.getFields());
+      for (let i = 0; i < fields.length; i++) {
+        collectReferencedTypes(fields[i].type, typeSet);
       }
     }
   }