Use nullish coalescing operator in all appropriate places (#2423)

Author: IvanGoncharov

src/__tests__/starWarsData.js

@@ -117,7 +117,7 @@ export type Droid = {|
  */
 function getCharacter(id) {
   // Returning a promise just to illustrate that GraphQL.js supports it.
-  return Promise.resolve(humanData[id] || droidData[id]);
+  return Promise.resolve(humanData[id] ?? droidData[id]);
 }
 
 /**

src/error/GraphQLError.js

@@ -148,7 +148,7 @@ export class GraphQLError extends Error {
       locations: {
         // Coercing falsy values to undefined ensures they will not be included
         // in JSON.stringify() when not provided.
-        value: _locations || undefined,
+        value: _locations ?? undefined,
         // By being enumerable, JSON.stringify will include `locations` in the
         // resulting output. This ensures that the simplest possible GraphQL
         // service adheres to the spec.
@@ -157,28 +157,28 @@ export class GraphQLError extends Error {
       path: {
         // Coercing falsy values to undefined ensures they will not be included
         // in JSON.stringify() when not provided.
-        value: path || undefined,
+        value: path ?? undefined,
         // By being enumerable, JSON.stringify will include `path` in the
         // resulting output. This ensures that the simplest possible GraphQL
         // service adheres to the spec.
         enumerable: path != null,
       },
       nodes: {
-        value: _nodes || undefined,
+        value: _nodes ?? undefined,
       },
       source: {
-        value: _source || undefined,
+        value: _source ?? undefined,
       },
       positions: {
-        value: _positions || undefined,
+        value: _positions ?? undefined,
       },
       originalError: {
         value: originalError,
       },
       extensions: {
         // Coercing falsy values to undefined ensures they will not be included
         // in JSON.stringify() when not provided.
-        value: _extensions || undefined,
+        value: _extensions ?? undefined,
         // By being enumerable, JSON.stringify will include `path` in the
         // resulting output. This ensures that the simplest possible GraphQL
         // service adheres to the spec.

src/error/formatError.js

@@ -12,7 +12,7 @@ import { type GraphQLError } from './GraphQLError';
  */
 export function formatError(error: GraphQLError): GraphQLFormattedError {
   devAssert(error, 'Received null or undefined error.');
-  const message = error.message || 'An unknown error occurred.';
+  const message = error.message ?? 'An unknown error occurred.';
   const locations = error.locations;
   const path = error.path;
   const extensions = error.extensions;

src/error/locatedError.js

@@ -22,7 +22,7 @@ export function locatedError(
 
   return new GraphQLError(
     originalError.message,
-    (originalError: any).nodes || nodes,
+    (originalError: any).nodes ?? nodes,
     (originalError: any).source,
     (originalError: any).positions,
     path,

src/execution/execute.js

@@ -314,12 +314,12 @@ export function buildExecutionContext(
   }
 
   /* istanbul ignore next (See https://github.com/graphql/graphql-js/issues/2203) */
-  const variableDefinitions = operation.variableDefinitions || [];
+  const variableDefinitions = operation.variableDefinitions ?? [];
 
   const coercedVariableValues = getVariableValues(
     schema,
     variableDefinitions,
-    rawVariableValues || {},
+    rawVariableValues ?? {},
     { maxErrors: 50 },
   );
 
@@ -334,8 +334,8 @@ export function buildExecutionContext(
     contextValue,
     operation,
     variableValues: coercedVariableValues.coerced,
-    fieldResolver: fieldResolver || defaultFieldResolver,
-    typeResolver: typeResolver || defaultTypeResolver,
+    fieldResolver: fieldResolver ?? defaultFieldResolver,
+    typeResolver: typeResolver ?? defaultTypeResolver,
     errors: [],
   };
 }
@@ -619,7 +619,7 @@ function resolveField(
     return;
   }
 
-  const resolveFn = fieldDef.resolve || exeContext.fieldResolver;
+  const resolveFn = fieldDef.resolve ?? exeContext.fieldResolver;
 
   const info = buildResolveInfo(
     exeContext,
@@ -961,7 +961,7 @@ function completeAbstractValue(
   path: Path,
   result: mixed,
 ): PromiseOrValue<ObjMap<mixed>> {
-  const resolveTypeFn = returnType.resolveType || exeContext.typeResolver;
+  const resolveTypeFn = returnType.resolveType ?? exeContext.typeResolver;
   const contextValue = exeContext.contextValue;
   const runtimeType = resolveTypeFn(result, contextValue, info, returnType);
 

src/execution/values.js

@@ -166,7 +166,7 @@ export function getArgumentValues(
   const coercedValues = {};
 
   /* istanbul ignore next (See https://github.com/graphql/graphql-js/issues/2203) */
-  const argumentNodes = node.arguments || [];
+  const argumentNodes = node.arguments ?? [];
   const argNodeMap = keyMap(argumentNodes, arg => arg.name.value);
 
   for (const argDef of def.args) {

src/language/lexer.js

@@ -66,7 +66,7 @@ export class Lexer {
     if (token.kind !== TokenKind.EOF) {
       do {
         // Note: next is only mutable during parsing, so we cast to allow this.
-        token = token.next || ((token: any).next = readToken(this, token));
+        token = token.next ?? ((token: any).next = readToken(this, token));
       } while (token.kind === TokenKind.COMMENT);
     }
     return token;

src/language/parser.js

@@ -1482,7 +1482,7 @@ class Parser {
    * is encountered.
    */
   unexpected(atToken?: ?Token): GraphQLError {
-    const token = atToken || this._lexer.token;
+    const token = atToken ?? this._lexer.token;
     return syntaxError(
       this._lexer.source,
       token.start,

src/language/printer.js

@@ -256,7 +256,7 @@ function addDescription(cb) {
  * print all items together separated by separator if provided
  */
 function join(maybeArray: ?Array<string>, separator = '') {
-  return maybeArray?.filter(x => x).join(separator) || '';
+  return maybeArray?.filter(x => x).join(separator) ?? '';
 }
 
 /**

src/language/visitor.js

@@ -332,7 +332,7 @@ export function visit(
     } else {
       stack = { inArray, index, keys, edits, prev: stack };
       inArray = Array.isArray(node);
-      keys = inArray ? node : visitorKeys[node.kind] || [];
+      keys = inArray ? node : visitorKeys[node.kind] ?? [];
       index = -1;
       edits = [];
       if (parent) {