repl: fix referrer for dynamic import

The ESM loader does not accept a directory as the referrer, it requires
a path within the directory.  Add `/repl` to ensure relative dynamic
imports can succeed.

Fixes: #19570

PR-URL: #30609
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Coe <bencoe@gmail.com>

lib/repl.js

@@ -324,10 +324,12 @@ function REPLServer(prompt,
     if (code === '\n')
       return cb(null);
 
-    let pwd;
+    let parentURL;
     try {
       const { pathToFileURL } = require('url');
-      pwd = pathToFileURL(process.cwd()).href;
+      // Adding `/repl` prevents dynamic imports from loading relative
+      // to the parent of `process.cwd()`.
+      parentURL = pathToFileURL(path.join(process.cwd(), 'repl')).href;
     } catch {
     }
     while (true) {
@@ -342,7 +344,7 @@ function REPLServer(prompt,
           filename: file,
           displayErrors: true,
           importModuleDynamically: experimentalModules ? async (specifier) => {
-            return asyncESM.ESMLoader.import(specifier, pwd);
+            return asyncESM.ESMLoader.import(specifier, parentURL);
           } : undefined
         });
       } catch (e) {

test/parallel/test-repl-import-referrer.js

@@ -0,0 +1,29 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cp = require('child_process');
+const fixtures = require('../common/fixtures');
+
+const args = [
+  '--interactive',
+  '--experimental-repl-await',
+  '--experimental-modules'
+];
+
+const opts = { cwd: fixtures.path('es-modules') };
+const child = cp.spawn(process.execPath, args, opts);
+
+let output = '';
+child.stdout.setEncoding('utf8');
+child.stdout.on('data', (data) => {
+  output += data;
+});
+
+child.on('exit', common.mustCall(() => {
+  const results = output.replace(/^> /mg, '').split('\n').slice(2);
+  assert.deepStrictEqual(results, ['[Module] { message: \'A message\' }', '']);
+}));
+
+child.stdin.write('await import(\'./message.mjs\');\n');
+child.stdin.write('.exit');
+child.stdin.end();