Fix React 19 webpack conditionNames to prevent react-server resolution

This fixes the webpack server bundle build errors where React was incorrectly
resolving to the react-server condition, causing missing exports for hooks
and Component class.

**Problem:**
- React 19 introduced conditional package exports with react-server condition
- Webpack 5 with target: 'node' was including react-server in conditionNames
- This caused RSCProvider/RSCRoute client components to fail with missing
  createContext, useContext, and Component exports

**Solution:**
- Explicitly set resolve.conditionNames to ['node', 'import', 'require', 'default']
- This matches webpack's defaults for node target but excludes react-server
- Server bundles now correctly use the full React build with hooks

**Changes:**
- Updated all serverWebpackConfig.js files to set explicit conditionNames
- Only RSC bundles should use react-server condition, not server-bundles

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

lib/generators/react_on_rails/templates/base/base/config/webpack/serverWebpackConfig.js.tt

@@ -114,13 +114,15 @@ const configureServer = () => {
   // If using the React on Rails Pro node server renderer, uncomment the next line
   // serverWebpackConfig.target = 'node'
 
-  // React 19 Fix: Explicitly set conditionNames to prevent resolving to react-server build
-  // The server bundle should use the regular React build, not the react-server build
-  // Only the RSC bundle should use react-server condition
+  // React 19 Fix: Prevent webpack from resolving to react-server condition
+  // The server-bundle needs the full React with hooks for SSR, not the react-server build
+  // Explicitly set conditionNames without react-server
   if (!serverWebpackConfig.resolve) {
     serverWebpackConfig.resolve = {};
   }
-  serverWebpackConfig.resolve.conditionNames = ['node', 'require', 'import', '...'];
+  // For target: 'node', webpack defaults to ['node', 'import', 'require', 'default']
+  // We explicitly list them to ensure react-server is not included
+  serverWebpackConfig.resolve.conditionNames = ['node', 'import', 'require', 'default'];
 
   return serverWebpackConfig;
 };

react_on_rails_pro/spec/dummy/config/webpack/serverWebpackConfig.js

@@ -123,13 +123,15 @@ const configureServer = (rscBundle = false) => {
 
   serverWebpackConfig.node = false;
 
-  // React 19 Fix: Explicitly set conditionNames to prevent resolving to react-server build
-  // The server bundle should use the regular React build, not the react-server build
-  // Only the RSC bundle should use react-server condition
+  // React 19 Fix: Prevent webpack from resolving to react-server condition
+  // The server-bundle needs the full React with hooks for SSR, not the react-server build
+  // Explicitly set conditionNames without react-server
   if (!serverWebpackConfig.resolve) {
     serverWebpackConfig.resolve = {};
   }
-  serverWebpackConfig.resolve.conditionNames = ['node', 'require', 'import', '...'];
+  // For target: 'node', webpack defaults to ['node', 'import', 'require', 'default']
+  // We explicitly list them to ensure react-server is not included
+  serverWebpackConfig.resolve.conditionNames = ['node', 'import', 'require', 'default'];
 
   return serverWebpackConfig;
 };

react_on_rails_pro/spec/execjs-compatible-dummy/config/webpack/serverWebpackConfig.js

@@ -112,13 +112,15 @@ const configureServer = () => {
   // If using the React on Rails Pro node server renderer, uncomment the next line
   // serverWebpackConfig.target = 'node'
 
-  // React 19 Fix: Explicitly set conditionNames to prevent resolving to react-server build
-  // The server bundle should use the regular React build, not the react-server build
-  // Only the RSC bundle should use react-server condition
+  // React 19 Fix: Prevent webpack from resolving to react-server condition
+  // The server-bundle needs the full React with hooks for SSR, not the react-server build
+  // Explicitly set conditionNames without react-server
   if (!serverWebpackConfig.resolve) {
     serverWebpackConfig.resolve = {};
   }
-  serverWebpackConfig.resolve.conditionNames = ['node', 'require', 'import', '...'];
+  // For target: 'node', webpack defaults to ['node', 'import', 'require', 'default']
+  // We explicitly list them to ensure react-server is not included
+  serverWebpackConfig.resolve.conditionNames = ['node', 'import', 'require', 'default'];
 
   return serverWebpackConfig;
 };

spec/dummy/config/webpack/serverWebpackConfig.js

@@ -110,13 +110,15 @@ const configureServer = () => {
   // If using the React on Rails Pro node server renderer, uncomment the next line
   // serverWebpackConfig.target = 'node'
 
-  // React 19 Fix: Explicitly set conditionNames to prevent resolving to react-server build
-  // The server bundle should use the regular React build, not the react-server build
-  // Only the RSC bundle should use react-server condition
+  // React 19 Fix: Prevent webpack from resolving to react-server condition
+  // The server-bundle needs the full React with hooks for SSR, not the react-server build
+  // Explicitly set conditionNames without react-server
   if (!serverWebpackConfig.resolve) {
     serverWebpackConfig.resolve = {};
   }
-  serverWebpackConfig.resolve.conditionNames = ['node', 'require', 'import', '...'];
+  // For target: 'node', webpack defaults to ['node', 'import', 'require', 'default']
+  // We explicitly list them to ensure react-server is not included
+  serverWebpackConfig.resolve.conditionNames = ['node', 'import', 'require', 'default'];
 
   return serverWebpackConfig;
 };