repl: fix repl crashing on variable declarations without init

dario-piotrowicz · web-flow · commit 049664bbdc42 · 2025-07-11T16:43:10.000Z
PR-URL: nodejs#59032 Fixes: nodejs#59029 Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com> Reviewed-By: Matthew Aitken <maitken033380023@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>
diff --git a/lib/repl.js b/lib/repl.js
@@ -1735,6 +1735,10 @@ function findExpressionCompleteTarget(code) {
   // what we can potentially complete on, so let's re-run the function's logic on that
   if (lastBodyStatement.type === 'VariableDeclaration') {
     const lastDeclarationInit = lastBodyStatement.declarations.at(-1).init;
+    if (!lastDeclarationInit) {
+      // If there is no initialization we can simply return
+      return null;
+    }
     const lastDeclarationInitCode = code.slice(lastDeclarationInit.start, lastDeclarationInit.end);
     return findExpressionCompleteTarget(lastDeclarationInitCode);
   }
diff --git a/test/parallel/test-repl-tab-complete.js b/test/parallel/test-repl-tab-complete.js
@@ -50,6 +50,12 @@ function prepareREPL() {
 }
 
 describe('REPL tab completion (core functionality)', () => {
+  it('does not break with variable declarations without an initialization', () => {
+    const { replServer } = prepareREPL();
+    replServer.complete('let a', getNoResultsFunction());
+    replServer.close();
+  });
+
   it('does not break in an object literal', () => {
     const { replServer, input } = prepareREPL();
 
