fix: some npm package uses array in package.json exports condition

lib/package-reader.js

@@ -398,13 +398,20 @@ function pickCondition(obj) {
   let env = process.env.NODE_ENV || '';
   if (env === 'undefined') env = '';
 
+  if (Array.isArray(obj)) {
+    for (const a of obj) {
+      const result = pickCondition(a);
+      if (result) return result;
+    }
+  }
+
   // use env (NODE_ENV) to support "development" and "production"
   for (const condition of ['import', 'module', 'browser', 'require', env, 'default']) {
     // Recursive call to support nested conditions.
     if (condition && condition in obj) return pickCondition(obj[condition]);
   }
 
-  return null;
+  throw new Error("Unexpected exports condition: " + JSON.stringify(obj));
 }
 
 function _exportsMain(exports) {

package.json

@@ -59,7 +59,7 @@
     "dumber-module-loader": "^1.2.5",
     "eslint-scope": "^8.0.2",
     "events": "^3.3.0",
-    "fs-browser-stub": "^1.0.1",
+    "fs-browser-stub": "^1.1.1",
     "https-browserify": "^1.0.0",
     "meriyah": "^6.0.1",
     "modify-code": "^2.1.4",

test/package-reader.spec.js

@@ -1723,7 +1723,7 @@ test('packageReader reads exports subpaths in package.json', async t => {
         ".": "./index.js",
         "./package.json": "./package.json",
         "./a": "./a.js",
-        "./b": "./be.js",
+        "./b": ["./be.js"],
         "./c": {"import": "./lib/c.js"},
         "./d/*": "./lib/d/*.js",
         "./e": null