fix(cli-repl): work around double-prompt Node.js REPL bug MONGOSH-727

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

@@ -220,6 +220,25 @@ describe('MongoshNodeRepl', () => {
       await waitEval(bus);
       expect(output).to.include('ISODate("2021-05-04T15:49:33.000Z")');
     });
+
+    it('handles a long series of errors', async function() {
+      input.write('-asdf();\n'.repeat(20));
+      await waitEval(bus);
+      expect(mongoshRepl.runtimeState().repl.listenerCount('SIGINT')).to.equal(1);
+    });
+
+    it('does not run statements that should not run', async() => {
+      input.write(`
+      sleep(0);
+      throw new Error();
+      if (false)
+        print ('!this should not run!');
+      `);
+      for (let i = 0; i < 20; i++) {
+        await tick();
+      }
+      expect(output).not.to.include('!this should not run!');
+    });
   });
 
   context('with terminal: true', () => {

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

@@ -9,8 +9,8 @@ import askpassword from 'askpassword';
 import { Console } from 'console';
 import { once } from 'events';
 import prettyRepl from 'pretty-repl';
-import { ReplOptions, REPLServer } from 'repl';
-import type { Readable, Writable } from 'stream';
+import { ReplOptions, REPLServer, start as replStart } from 'repl';
+import { Readable, Writable, PassThrough } from 'stream';
 import type { ReadStream, WriteStream } from 'tty';
 import { callbackify, promisify } from 'util';
 import * as asyncRepl from './async-repl';
@@ -56,6 +56,40 @@ type Mutable<T> = {
   -readonly[P in keyof T]: T[P]
 };
 
+// https://github.com/nodejs/node/pull/38314
+function fixupReplForNodeBug38314(repl: REPLServer): void {
+  {
+    // Check whether bug is present:
+    const input = new PassThrough();
+    const output = new PassThrough();
+    const evalFn = (code: any, ctx: any, filename: any, cb: any) => cb(new Error('err'));
+    const prompt = 'prompt#';
+    replStart({ input, output, eval: evalFn as any, prompt });
+    input.end('s\n');
+    if (!String(output.read()).includes('prompt#prompt#')) {
+      return; // All good, nothing to do here.
+    }
+  }
+
+  // If it is, fix up the REPL's domain 'error' listener to not call displayPrompt()
+  const domain = (repl as any)._domain;
+  const domainErrorListeners = domain.listeners('error');
+  const origListener = domainErrorListeners.find((fn: any) => fn.name === 'debugDomainError');
+  if (!origListener) {
+    throw new Error('Could not find REPL domain error listener');
+  }
+  domain.removeListener('error', origListener);
+  domain.on('error', function(this: any, err: Error) {
+    const origDisplayPrompt = repl.displayPrompt;
+    repl.displayPrompt = () => {};
+    try {
+      origListener.call(this, err);
+    } finally {
+      repl.displayPrompt = origDisplayPrompt;
+    }
+  });
+}
+
 /**
  * An instance of a `mongosh` REPL, without any of the actual I/O.
  */
@@ -113,6 +147,7 @@ class MongoshNodeRepl implements EvaluationListener {
         (err: Error) => Object.assign(new MongoshInternalError(err.message), { stack: err.stack }),
       ...this.nodeReplOptions
     });
+    fixupReplForNodeBug38314(repl);
 
     const console = new Console({
       stdout: this.output,

packages/cli-repl/test/e2e.spec.ts

@@ -8,7 +8,7 @@ import { promises as fs, createReadStream } from 'fs';
 import { promisify } from 'util';
 import rimraf from 'rimraf';
 import path from 'path';
-import { readReplLogfile, hasNodeBug38314 } from './repl-helpers';
+import { readReplLogfile } from './repl-helpers';
 
 describe('e2e', function() {
   const testServer = startTestServer('shared');
@@ -558,8 +558,6 @@ describe('e2e', function() {
       let result;
       result = await shell.executeLine('require("a")');
       expect(result).to.match(/Error: Cannot find module 'a'/);
-      // Wait for double prompt because of Node.js REPL bug
-      if (hasNodeBug38314()) await eventually(() => shell.assertContainsOutput('> > '));
       result = await shell.executeLine('require("./a")');
       expect(result).to.match(/^A$/m);
       result = await shell.executeLine('require("b")');

packages/cli-repl/test/repl-helpers.ts

@@ -7,8 +7,6 @@ import chai, { expect } from 'chai';
 import sinon from 'ts-sinon';
 import sinonChai from 'sinon-chai';
 import chaiAsPromised from 'chai-as-promised';
-import repl from 'repl';
-import { PassThrough } from 'stream';
 import type { MongoshBus, MongoshBusEventsMap } from '@mongosh/types';
 
 chai.use(sinonChai);
@@ -78,17 +76,6 @@ async function readReplLogfile(logPath: string) {
     .map((line) => JSON.parse(line));
 }
 
-// https://github.com/nodejs/node/pull/38314
-function hasNodeBug38314() {
-  const input = new PassThrough();
-  const output = new PassThrough();
-  const evalFn = (code, ctx, filename, cb) => cb(new Error('err'));
-  const prompt = 'prompt#';
-  repl.start({ input, output, eval: evalFn, prompt });
-  input.end('s\n');
-  return String(output.read()).includes('prompt#prompt#');
-}
-
 export {
   expect,
   sinon,
@@ -98,6 +85,5 @@ export {
   waitEval,
   waitCompletion,
   fakeTTYProps,
-  readReplLogfile,
-  hasNodeBug38314
+  readReplLogfile
 };