repl: fix repl crashing on variable declarations without init

PR-URL: #59032Fixes: #59029 Reviewed-By: Yagiz Nizipli <[email protected]> Reviewed-By: Matthew Aitken <[email protected]> Reviewed-By: James M Snell <[email protected]>

Author: dario-piotrowicz

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'){
 constlastDeclarationInit=lastBodyStatement.declarations.at(-1).init;
+if(!lastDeclarationInit){
+// If there is no initialization we can simply return
+returnnull;
+}
 constlastDeclarationInitCode=code.slice(lastDeclarationInit.start,lastDeclarationInit.end);
 returnfindExpressionCompleteTarget(lastDeclarationInitCode);
 }

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();