Fix NEXT_PUBLIC env values not being inlined (#11896)

* Clean up env tests a bit

* Fix NEXT_PUBLIC env values not being inlined
Co-authored-by: NJoe Haddad <joe.haddad@zeit.co>

packages/next/build/webpack-config.ts

@@ -769,7 +769,7 @@ export default async function getBaseWebpackConfig(
           ? Object.keys(process.env).reduce(
               (prev: { [key: string]: string }, key: string) => {
                 if (key.startsWith('NEXT_PUBLIC_')) {
-                  prev[key] = process.env[key]!
+                  prev[`process.env.${key}`] = JSON.stringify(process.env[key]!)
                 }
                 return prev
               },

test/integration/env-config/app/next.config.js

+module.exports = {
+  experimental: {
+    pageEnv: true,
+
+    async redirects() {
+      return [
+        {
+          source: '/hello',
+          permanent: false,
+          destination: `/${process.env.NEXT_PUBLIC_TEST_DEST}`,
+        },
+      ]
+    },
+  },
+}

test/integration/env-config/app/pages/next-config-loaded-env.js

-export default () => (
-  <p>
-    {JSON.stringify({
-      LOCAL_ENV_FILE_KEY: process.env.NC_LOCAL_ENV_FILE_KEY,
-      ENV_FILE_KEY: process.env.NC_ENV_FILE_KEY,
-      PRODUCTION_ENV_FILE_KEY: process.env.NC_PRODUCTION_ENV_FILE_KEY,
-      LOCAL_PRODUCTION_ENV_FILE_KEY:
-        process.env.NC_LOCAL_PRODUCTION_ENV_FILE_KEY,
-      DEVELOPMENT_ENV_FILE_KEY: process.env.NC_DEVELOPMENT_ENV_FILE_KEY,
-      TEST_ENV_FILE_KEY: process.env.NC_TEST_ENV_FILE_KEY,
-      LOCAL_TEST_ENV_FILE_KEY: process.env.NC_LOCAL_TEST_ENV_FILE_KEY,
-      LOCAL_DEVELOPMENT_ENV_FILE_KEY:
-        process.env.NC_LOCAL_DEVELOPMENT_ENV_FILE_KEY,
-    })}
-  </p>
-)