Don't use nested objects to "namespace" namespace constants (#21073)

packages/react-dom/src/client/ReactDOMComponent.js

@@ -54,7 +54,7 @@ import {
   setValueForStyles,
   validateShorthandPropertyCollisionInDev,
 } from '../shared/CSSPropertyOperations';
-import {Namespaces, getIntrinsicNamespace} from '../shared/DOMNamespaces';
+import {HTML_NAMESPACE, getIntrinsicNamespace} from '../shared/DOMNamespaces';
 import {
   getPropertyInfo,
   shouldIgnoreAttribute,
@@ -86,8 +86,6 @@ const CHILDREN = 'children';
 const STYLE = 'style';
 const HTML = '__html';
 
-const {html: HTML_NAMESPACE} = Namespaces;
-
 let warnedUnknownTags;
 let suppressHydrationWarning;
 

packages/react-dom/src/client/setInnerHTML.js

@@ -7,7 +7,7 @@
  * @flow
  */
 
-import {Namespaces} from '../shared/DOMNamespaces';
+import {SVG_NAMESPACE} from '../shared/DOMNamespaces';
 import createMicrosoftUnsafeLocalFunction from '../shared/createMicrosoftUnsafeLocalFunction';
 import {enableTrustedTypesIntegration} from 'shared/ReactFeatureFlags';
 
@@ -25,7 +25,7 @@ const setInnerHTML = createMicrosoftUnsafeLocalFunction(function(
   node: Element,
   html: {valueOf(): {toString(): string, ...}, ...},
 ): void {
-  if (node.namespaceURI === Namespaces.svg) {
+  if (node.namespaceURI === SVG_NAMESPACE) {
     if (__DEV__) {
       if (enableTrustedTypesIntegration) {
         // TODO: reconsider the text of this warning and when it should show

packages/react-dom/src/server/ReactPartialRenderer.js

@@ -63,7 +63,7 @@ import {
   setCurrentPartialRenderer,
 } from './ReactPartialRendererHooks';
 import {
-  Namespaces,
+  HTML_NAMESPACE,
   getIntrinsicNamespace,
   getChildNamespace,
 } from '../shared/DOMNamespaces';
@@ -747,7 +747,7 @@ class ReactDOMServerRenderer {
       type: null,
       // Assume all trees start in the HTML namespace (not totally true, but
       // this is what we did historically)
-      domNamespace: Namespaces.html,
+      domNamespace: HTML_NAMESPACE,
       children: flatChildren,
       childIndex: 0,
       context: emptyObject,
@@ -1327,12 +1327,12 @@ class ReactDOMServerRenderer {
     const tag = element.type.toLowerCase();
 
     let namespace = parentNamespace;
-    if (parentNamespace === Namespaces.html) {
+    if (parentNamespace === HTML_NAMESPACE) {
       namespace = getIntrinsicNamespace(tag);
     }
 
     if (__DEV__) {
-      if (namespace === Namespaces.html) {
+      if (namespace === HTML_NAMESPACE) {
         // Should this check be gated by parent namespace? Not sure we want to
         // allow <SVG> or <mATH>.
         if (tag !== element.type) {

packages/react-dom/src/shared/DOMNamespaces.js

@@ -5,15 +5,9 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-const HTML_NAMESPACE = 'http://www.w3.org/1999/xhtml';
-const MATH_NAMESPACE = 'http://www.w3.org/1998/Math/MathML';
-const SVG_NAMESPACE = 'http://www.w3.org/2000/svg';
-
-export const Namespaces = {
-  html: HTML_NAMESPACE,
-  mathml: MATH_NAMESPACE,
-  svg: SVG_NAMESPACE,
-};
+export const HTML_NAMESPACE = 'http://www.w3.org/1999/xhtml';
+export const MATH_NAMESPACE = 'http://www.w3.org/1998/Math/MathML';
+export const SVG_NAMESPACE = 'http://www.w3.org/2000/svg';
 
 // Assumes there is no parent namespace.
 export function getIntrinsicNamespace(type: string): string {