add back yarn pnp check with different error message (#403)

.changeset/strange-pianos-fry.md

@@ -1,5 +1,5 @@
 ---
-'@cloudflare/next-on-pages': minor
+'@cloudflare/next-on-pages': patch
 ---
 
-allow next-on-pages applications to be built using `yarn pnp`
+clarify that Yarn Plug'n'Play can't be used simply because not supported by vercel

packages/next-on-pages/package.json

@@ -37,6 +37,7 @@
 		"chokidar": "^3.5.3",
 		"cookie": "^0.5.0",
 		"esbuild": "^0.15.3",
+		"js-yaml": "^4.1.0",
 		"pcre-to-regexp": "^1.1.0",
 		"semver": "^7.5.2",
 		"zod": "^3.21.4",
@@ -52,6 +53,7 @@
 		"@cloudflare/workers-types": "^4.20230404.0",
 		"@tsconfig/strictest": "^2.0.0",
 		"@types/cookie": "^0.5.1",
+		"@types/js-yaml": "^4.0.5",
 		"@types/mock-fs": "^4.13.1",
 		"@types/node": "^20.1.4",
 		"dedent-tabs": "^0.10.3",

packages/next-on-pages/src/buildApplication/packageManagerUtils.ts

@@ -1,4 +1,6 @@
 import { execFileSync, spawn } from 'child_process';
+import { readFile } from 'fs/promises';
+import YAML from 'js-yaml';
 import { cliError } from '../cli';
 import { validateFile } from '../utils';
 
@@ -28,6 +30,24 @@ export async function getCurrentPackageManager(): Promise<PackageManager> {
 			});
 		});
 		if (!yarnV.startsWith('1.')) {
+			const yarnrc = await readFile('.yarnrc.yml', 'utf-8');
+			const { nodeLinker } = YAML.load(yarnrc) as {
+				nodeLinker: string;
+			};
+			if (nodeLinker !== 'node-modules') {
+				cliError(
+					`
+					Error: Yarn Plug'n'Play not supported
+
+					The vercel cli doesn't currently support Plug'n'Play features from yarn berry.
+					Since @cloudflare/next-on-pages uses the vercel cli to build the target application,
+					if you want to use the adapter with yarn berry, you need to add "nodeLinker: node-modules"
+					to your .yarnrc.yml
+				`,
+					{ spaced: true },
+				);
+				process.exit(1);
+			}
 			return 'yarn (berry)';
 		} else {
 			return 'yarn (classic)';