fix(history): do not modify empty history MONGOSH-722

packages/cli-repl/src/mongosh-repl.spec.ts

@@ -415,6 +415,13 @@ describe('MongoshNodeRepl', () => {
               'const a = 20'
             ]);
           });
+
+          it('does not crash if hitting enter and then up', async() => {
+            input.write('\n');
+            await once(mongoshRepl.runtimeState().repl, 'flushHistory');
+            input.write(`${arrowUp}`);
+            await tick();
+          });
         });
       }
     });

packages/history/src/history.spec.ts

@@ -33,6 +33,12 @@ describe('changeHistory', () => {
       changeHistory(cloned);
       expect(cloned).to.deep.equal(i);
     });
+
+    it('does not modify an empty history', () => {
+      const i: string[] = [];
+      changeHistory(i);
+      expect(i).to.deep.equal([]);
+    });
   });
 
   context('when redact option is false', () => {

packages/history/src/history.ts

@@ -17,6 +17,7 @@ export function removeCommand(history: string, redact = false): string {
  * @param {boolean} redact - Option to redact sensitive info.
  */
 export function changeHistory(history: string[], redact = false): void {
+  if (history.length === 0) return;
   const hiddenCommands = new RegExp(HIDDEN_COMMANDS, 'g');
 
   if (hiddenCommands.test(history[0])) {