fix: don't emit changes when the helmetData wrapper object changes

This makes the context free enviornment behave like a context environment,
for example, the outer context could be destroyed and recreated, and emiting
changes isn't effected. The helmetData should behave the same.

__tests__/server/helmetData.test.js

@@ -76,14 +76,13 @@ describe('Helmet Data', () => {
 
     it('works with the same context object but separate HelmetData instances', () => {
       const context = {};
-      const instances = [];
 
       render(
         <div>
-          <Helmet helmetData={new HelmetData(context, instances)}>
+          <Helmet helmetData={new HelmetData(context)}>
             <base href="http://mysite.com" />
           </Helmet>
-          <Helmet helmetData={new HelmetData(context, instances)}>
+          <Helmet helmetData={new HelmetData(context)}>
             <base href="http://mysite.com/public" />
           </Helmet>
         </div>

index.d.ts

@@ -81,7 +81,7 @@ declare module 'react-helmet-async' {
   }
 
   export class HelmetData {
-    constructor(context: any, instances?: Array<any>)
+    constructor(context: any)
   }
 
   export class HelmetProvider extends React.Component<ProviderProps> {

src/index.js

@@ -5,13 +5,13 @@ import invariant from 'invariant';
 import { Context } from './Provider';
 import HelmetData from './HelmetData';
 import Dispatcher from './Dispatcher';
+import { without } from './utils';
 import { TAG_NAMES, VALID_TAG_NAMES, HTML_TAG_MAP } from './constants';
 
 export { default as HelmetData } from './HelmetData';
 export { default as HelmetProvider } from './Provider';
 
 /* eslint-disable class-methods-use-this */
-
 export class Helmet extends Component {
   /**
    * @param {Object} base: {"target": "_blank", "href": "http://mysite.com/"}
@@ -63,7 +63,7 @@ export class Helmet extends Component {
   static displayName = 'Helmet';
 
   shouldComponentUpdate(nextProps) {
-    return !fastCompare(this.props, nextProps);
+    return !fastCompare(without(this.props, 'helmetData'), without(nextProps, 'helmetData'));
   }
 
   mapNestedChildrenToProps(child, nestedChildren) {
@@ -235,7 +235,7 @@ export class Helmet extends Component {
 
     return helmetData ? (
       // eslint-disable-next-line react/jsx-props-no-spreading
-      <Dispatcher {...newProps} context={helmetData.value} />
+      <Dispatcher {...newProps} context={helmetData.value} helmetData={undefined} />
     ) : (
       <Context.Consumer>
         {(

src/utils.js

@@ -250,3 +250,10 @@ export const prioritizer = (elementsList, propsToMatch) => {
   }
   return { default: elementsList };
 };
+
+export const without = (obj, key) => {
+  return {
+    ...obj,
+    [key]: undefined,
+  };
+};