Enable devMode with react-native init-windows old/* templates (#13362)

## Description

The `init-windows` CLI command can be used to create apps with the old arch templates, but "devMode" (i.e. using your local, linked RNW repo instead of the package from NPM) didn't work.

This PR fixes that functionality so `init-windows` can become the new method.

### Type of Change
- Bug fix (non-breaking change which fixes an issue)

### Why
We want `init-windows` to be the default method for creating new RNW projects, but it still needs to support the old templates for now, and this was the last "missing" feature.

### What
Switched the old templates to using the same `metro.config.js` file that the new templates use (with devMode template variable) and also piping through the correct value for that variable.

## Screenshots
N/A

## Testing
Verified I could create a new (old) app locally with linked RNW and it recognized and implemented devMode correctly, so that the app could launch.

## Changelog
Should this change be included in the release notes: yes

Enabled detecting devMode with `react-native init-window`s and the old/* templates

change/@react-native-windows-cli-71dd315f-09df-4544-b24b-bbd0176c4069.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Enable devMode with react-native init-windows old/* templates",
+  "packageName": "@react-native-windows/cli",
+  "email": "jthysell@microsoft.com",
+  "dependentChangeType": "patch"
+}

change/react-native-windows-a6820d65-30e4-4680-9f68-0647449a79ba.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Enable devMode with react-native init-windows old/* templates",
+  "packageName": "react-native-windows",
+  "email": "jthysell@microsoft.com",
+  "dependentChangeType": "patch"
+}

packages/@react-native-windows/cli/src/generator-windows/index.ts

@@ -203,6 +203,8 @@ export async function copyProjectTemplateAndReplace(
     packageGuid: packageGuid,
     currentUser: currentUser,
 
+    devMode: options.useDevMode,
+
     useExperimentalNuget: options.experimentalNuGetDependency,
     nuGetTestFeed: options.nuGetTestFeed,
     nuGetADOFeed: nugetVersion.startsWith('0.0.0-'),
@@ -230,12 +232,7 @@ export async function copyProjectTemplateAndReplace(
       ? [
           // app common mappings
           {
-            from: path.join(
-              srcRootPath,
-              options.useDevMode
-                ? 'metro.devMode.config.js'
-                : 'metro.config.js',
-            ),
+            from: path.join(srcRootPath, 'metro.config.js'),
             to: 'metro.config.js',
           },
           {

vnext/template/metro.config.js

@@ -8,6 +8,11 @@ const rnwPath = fs.realpathSync(
   path.resolve(require.resolve('react-native-windows/package.json'), '..'),
 );
 
+//{{#devMode}} [devMode
+const rnwRootNodeModules = path.resolve(rnwPath, '..', 'node_modules');
+const rnwPackages = path.resolve(rnwPath, '..', 'packages');
+// devMode]{{/devMode}}
+
 /**
  * Metro configuration
  * https://facebook.github.io/metro/docs/configuration
@@ -16,6 +21,9 @@ const rnwPath = fs.realpathSync(
  */
 
 const config = {
+  //{{#devMode}} [devMode
+  watchFolders: [rnwPath, rnwRootNodeModules, rnwPackages],
+  // devMode]{{/devMode}}
   resolver: {
     blockList: exclusionList([
       // This stops "react-native run-windows" from causing the metro server to crash if its already running
@@ -27,6 +35,11 @@ const config = {
       new RegExp(`${rnwPath}/target/.*`),
       /.*\.ProjectImports\.zip/,
     ]),
+    //{{#devMode}} [devMode
+    extraNodeModules: {
+      'react-native-windows': rnwPath,
+    },
+    // devMode]{{/devMode}}
   },
   transformer: {
     getTransformOptions: async () => ({
@@ -35,8 +48,6 @@ const config = {
         inlineRequires: true,
       },
     }),
-    // This fixes the 'missing-asset-registry-path` error (see https://github.com/microsoft/react-native-windows/issues/11437)
-    assetRegistryPath: 'react-native/Libraries/Image/AssetRegistry',
   },
 };
 

vnext/templates/old/generateWrapper.js

@@ -7,6 +7,7 @@
  */
 
 const generateWindows = require('../../generate');
+const templateUtils = require('../templateUtils');
 
 function makeGenerateWindowsWrapper(
   language = 'cpp',
@@ -33,6 +34,8 @@ function makeGenerateWindowsWrapper(
   const postInstall = async (config = {}, options = {}) => {
     const experimentalFeatures = config?.project?.windows?.experimentalFeatures;
 
+    const rnwInfo = templateUtils.getRnwInfo(config, options);
+
     const generateOptions = {
       overwrite: !!options.overwrite,
       language,
@@ -41,7 +44,7 @@ function makeGenerateWindowsWrapper(
         experimentalFeatures?.UseExperimentalNuget ?? false,
       useWinUI3: experimentalFeatures?.UseWinUI3 ?? false,
       useHermes: experimentalFeatures?.UseHermes ?? true,
-      useDevMode: false,
+      useDevMode: rnwInfo.devMode,
       verbose: !!options.logging,
       telemetry: !!options.telemetry,
     };