readline: fix to not access a property on an undefined value

PR-URL: #43543 Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Tobias Nießen <[email protected]> Reviewed-By: Yongsheng Zhang <[email protected]> Reviewed-By: James M Snell <[email protected]>
nodejs · Jul 31, 2022 · 67e91aa · 67e91aa
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diff --git a/lib/internal/readline/utils.js b/lib/internal/readline/utils.js
@@ -366,6 +366,9 @@ function* emitKeys(stream) {
 
 // This runs in O(n log n).
 function commonPrefix(strings) {
+  if (strings.length === 0) {
+    return '';
+  }
   if (strings.length === 1) {
     return strings[0];
   }

diff --git a/test/parallel/test-repl-tab-complete-on-editor-mode.js b/test/parallel/test-repl-tab-complete-on-editor-mode.js
@@ -0,0 +1,21 @@
+'use strict';
+
+require('../common');
+const ArrayStream = require('../common/arraystream');
+const repl = require('repl');
+
+const stream = new ArrayStream();
+const replServer = repl.start({
+  input: stream,
+  output: stream,
+  terminal: true,
+});
+
+// Editor mode
+replServer.write('.editor\n');
+
+// Regression test for https://github.com/nodejs/node/issues/43528
+replServer.write('a');
+replServer.write(null, { name: 'tab' }); // Should not throw
+
+replServer.close();