repl: do not run --eval code if there is none

`getOptionValue('--eval')` always returns a string, so it is never
loose-equal to `null`. Running eval makes some modifications to the
global object, including setting `module` to a different value, which
we want to avoid if possible.

Refs: https://github.com/nodejs/node/pull/27278
PR-URL: https://github.com/nodejs/node/pull/27587
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: John-David Dalton <john.david.dalton@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/test/parallel/test-repl-cli-eval.js b/test/parallel/test-repl-cli-eval.js
new file mode 100644
index 0000000000..6069a20957
--- /dev/null
+++ b/test/parallel/test-repl-cli-eval.js
@@ -0,0 +1,22 @@
+'use strict';
+const common = require('../common');
+const child_process = require('child_process');
+const assert = require('assert');
+
+// Regression test for https://github.com/nodejs/node/issues/27575:
+// module.id === '<repl>' in the REPL.
+
+for (const extraFlags of [[], ['-e', '42']]) {
+  const flags = ['--interactive', ...extraFlags];
+  const proc = child_process.spawn(process.execPath, flags, {
+    stdio: ['pipe', 'pipe', 'inherit']
+  });
+  proc.stdin.write('module.id\n.exit\n');
+
+  let stdout = '';
+  proc.stdout.setEncoding('utf8');
+  proc.stdout.on('data', (chunk) => stdout += chunk);
+  proc.stdout.on('end', common.mustCall(() => {
+    assert(stdout.includes('<repl>'), `stdout: ${stdout}`);
+  }));
+}