Fix RSC test infrastructure: Convert jest.setup.js to ESM and re-enable tests

- Convert jest.setup.js from CommonJS require() to ESM imports for compatibility
  with ESM mode
- Re-enable RSC tests with automatic React version detection:
  - Tests run normally on React 19+ where RSC features are available
  - Tests skip gracefully on React 18 with informative message
- Remove unnecessary script/convert override since package.json now handles
  version checking automatically

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

Co-Authored-By: Claude <[email protected]>

Author: justin808

packages/react-on-rails-pro/package.json

@@ -9,7 +9,7 @@
     "clean": "rm -rf ./lib",
     "test": "pnpm run test:non-rsc && pnpm run test:rsc",
     "test:non-rsc": "jest tests --testPathIgnorePatterns=\".*(RSC|stream|registerServerComponent|serverRenderReactComponent|SuspenseHydration).*\"",
-    "test:rsc": "echo 'TODO: RSC tests disabled - jest.setup.js uses require() incompatible with ESM mode. Re-enable after converting setup to ESM.' && exit 0",
+    "test:rsc": "node scripts/check-react-version.cjs || NODE_CONDITIONS=react-server jest tests/*.rsc.test.*",
     "type-check": "tsc --noEmit --noErrorTruncation",
     "prepare": "[ -f lib/ReactOnRails.full.js ] || (rm -rf ./lib && tsc)",
     "prepublishOnly": "pnpm run build",

packages/react-on-rails-pro/tests/jest.setup.js

@@ -1,3 +1,8 @@
+import { TextEncoder, TextDecoder } from 'util';
+import { Readable } from 'stream';
+import { ReadableStream, ReadableStreamDefaultReader } from 'stream/web';
+import { jest } from '@jest/globals';
+
 // If jsdom environment is set and TextEncoder is not defined, then define TextEncoder and TextDecoder
 // The current version of jsdom does not support TextEncoder and TextDecoder
 // The following code will tell us when jsdom supports TextEncoder and TextDecoder
@@ -11,13 +16,6 @@ if (typeof window !== 'undefined' && typeof window.MessageChannel !== 'undefined
 }
 
 if (typeof window !== 'undefined') {
-  // eslint-disable-next-line global-require
-  const { TextEncoder, TextDecoder } = require('util');
-  // eslint-disable-next-line global-require
-  const { Readable } = require('stream');
-  // eslint-disable-next-line global-require
-  const { ReadableStream, ReadableStreamDefaultReader } = require('stream/web');
-
   // Mock the fetch function to return a ReadableStream instead of Node's Readable stream
   // This matches browser behavior where fetch responses have ReadableStream bodies
   // Node's fetch and polyfills like jest-fetch-mock return Node's Readable stream,

script/convert

@@ -53,12 +53,8 @@ gsub_file_content(
   '"test:non-rsc": "jest tests --testPathIgnorePatterns=\".*(RSC|stream|' \
   'registerServerComponent|serverRenderReactComponent|SuspenseHydration).*\"",'
 )
-# Make test:rsc script do nothing
-gsub_file_content(
-  "../packages/react-on-rails-pro/package.json",
-  /"test:rsc": "(?:\\"|[^"])*",/,
-  '"test:rsc": "exit 0",'
-)
+# test:rsc script now automatically detects React version and skips on React 18
+# No override needed - the script checks React version and exits cleanly if < 19
 # Keep modern JSX transform for React 18+
 # gsub_file_content("../tsconfig.json", "react-jsx", "react")
 # gsub_file_content("../spec/dummy/babel.config.js", "runtime: 'automatic'", "runtime: 'classic'")