Only use Rollup's CommonJS plugin for "react-art" (#18186)

* Only use Rollup's CommonJS plugin for "react-art"

We still need it for the "art" UMD builds but nothing else should have
CommonJS dependencies anymore.

* react-debug-tools and jest-react should leave object-assign as an external dep

This avoids it being compiled into the output.

Author: sebmarkbage

packages/jest-react/package.json

@@ -23,6 +23,9 @@
     "react": "^16.0.0",
     "react-test-renderer": "^16.0.0"
   },
+  "dependencies": {
+    "object-assign": "^4.1.1"
+  },
   "files": [
     "LICENSE",
     "README.md",

packages/react-debug-tools/package.json

@@ -29,6 +29,7 @@
     "react": "^16.0.0"
   },
   "dependencies": {
-    "error-stack-parser": "^2.0.2"
+    "error-stack-parser": "^2.0.2",
+    "object-assign": "^4.1.1"
   }
 }

scripts/rollup/build.js

@@ -392,8 +392,10 @@ function getPlugins(
       'process.env.NODE_ENV': isProduction ? "'production'" : "'development'",
       __EXPERIMENTAL__,
     }),
-    // We still need CommonJS for external deps like object-assign.
-    commonjs(),
+    // The CommonJS plugin *only* exists to pull "art" into "react-art".
+    // I'm going to port "art" to ES modules to avoid this problem.
+    // Please don't enable this for anything else!
+    isUMDBundle && entry === 'react-art' && commonjs(),
     // Apply dead code elimination and/or minification.
     isProduction &&
       closure(