repl: add replDefaults to customize the writer

So far it was not possible to modify the inspection defaults used by
the REPL from the running instance itself. This introduces a new
property on `util.inspect` which is only used inside the REPL and which
allows to modify the used inspection defaults at any point of time.

PR-URL: https://github.com/nodejs/node/pull/26375
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/test/parallel/test-repl-inspect-defaults.js b/test/parallel/test-repl-inspect-defaults.js
new file mode 100644
index 0000000000..a73bc792fe
--- /dev/null
+++ b/test/parallel/test-repl-inspect-defaults.js
@@ -0,0 +1,29 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cp = require('child_process');
+const child = cp.spawn(process.execPath, ['-i']);
+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');
+  assert.deepStrictEqual(
+    results,
+    [
+      '[ 42, 23 ]',
+      '1',
+      '[ 42, ... 1 more item ]',
+      ''
+    ]
+  );
+}));
+
+child.stdin.write('[ 42, 23 ]\n');
+child.stdin.write('util.inspect.replDefaults.maxArrayLength = 1\n');
+child.stdin.write('[ 42, 23 ]\n');
+child.stdin.end();