node inspect crashes when tab-completing with a require

[langdon-holly]

• Version: v11.1.0
• Platform: Linux setp 4.19.1-arch1-1-ARCH Make it work like the real thing node-inspect#1 SMP PREEMPT Sun Nov 4 16:49:26 UTC 2018 x86_64 GNU/Linux
• Subsystem:

Steps to reproduce:

0. Create an empty file named "test.js"
1. Run node inspect test.js
2. Enter the debug repl
3. Type require("
4. Press tab

Result: Node prints the following message to standard error, then exits with status 1.

There was an internal error in node-inspect. Please report this bug.
Cannot read property 'extensions' of undefined
TypeError: Cannot read property 'extensions' of undefined
    at REPLServer.complete (repl.js:1031:51)
    at REPLServer.completer (repl.js:492:14)
    at REPLServer.Interface._tabComplete (readline.js:476:8)
    at REPLServer.Interface._ttyWrite (readline.js:975:16)
    at REPLServer.self._ttyWrite (repl.js:719:7)
    at ReadStream.onkeypress (readline.js:178:10)
    at ReadStream.emit (events.js:182:13)
    at ReadStream.EventEmitter.emit (domain.js:441:20)
    at emitKeys (internal/readline.js:424:14)
    at emitKeys.next (<anonymous>)

Observed rules for reproduction:

• test.js can be any JavaScript file.
• A single quote may be substituted for the double quote in step 3.
• require(" may be preceded by any JavaScript code.
• Space characters may be typed between require and (".
• The paren must be immediately followed by the quote (no whitespace).
• Any additional characters may be typed before pressing tab.
• The cursor must be somewhere after the quote when pressing tab.

[Trott]

@jkrems Should this bug report be transferred to https://github.com/nodejs/node-inspect? Or is this the better location for it?

[jkrems]

I think it would be best to transfer it to node-inspect since that is where it would need to be fixed.

[Trott]

I think it would be best to transfer it to node-inspect since that is where it would need to be fixed.

Done!

[militello]

I had the same problem, the cause was using vm context:
const vm = require('vm');
r.context = vm.createContext(mycontext);
changed to use context directly and it works again
r.context.something = something

[Trott]

I'm unable to reproduce this bug. @langdon-holly Are you still seeing this issue in Node.js 16.x or 14.x?

[langdon-holly]

@Trott I am unable to reproduce in v16.0.0.

[militello]

I was using 14.15.0

[militello]

This code is failing on LTS (tested on 14.15.0 / 14.16.1) with the problem reported:

const repl = require('repl');
const r = repl.start('teste> ');

const context = { x: 1, y: 2 };
r.context = require('vm').createContext(context);

It's the first time I create my own REPL so could be my mistake...

But if the problem is just with the auto-complete, if it was caught we could still require (without auto-complete) and continue to use the REPL.

This works...

const repl = require('repl');
const r = repl.start('teste> ');

r.context.x = 1;
r.context.y = 2;

[militello]

Is there any better way to make a complex context from an object to use in REPL?

[Trott]

@langdon-holly I'm curious if this might be Linux distribution and/or processor specific. I just installed an Ubuntu docker image on macOS, then used nvm to install Node.js 11.1.0 and could not reproduce. (I thought maybe I had to use Linux to replicate, but apparently it would be more than just that.)

[langdon-holly]

I doubt it's processor-specific, but it could be OS-specific. I just tried node v11.1.0 on Arch Linux, again, and was able to reproduce. I also briefly looked at the source code, and it appears that the crash occurs at repl.js:1031 when completing a require, when the REPLServer's context has no 'require' property. Perhaps the OS or installation details affect the REPLServer's context?

[militello]

I'm running on ubuntu 20 here. Installed Node via ASDF.

[jkrems]

For the original bug (require combined with tab completion): There's something special about require in the context of the debugger. We inject a runtime API for require which allows it to work in the debug repl (or Chrome DevTools console) without a "real" global require when not stopped in a callstack frame with a require in scope.

The exception looks like the REPL code to auto-complete require paths blindly assumes that any require would have a extensions property - but the runtime API one doesn't have any properties. So maybe the answer here is to add defensive code to the REPL server code? See:

node/lib/repl.js

Line 1228 in a03d3af

const extensions = ObjectKeys(this.context.require.extensions);

The require function in the command line API is set up here:

node/lib/internal/util/inspector.js

Lines 25 to 37 in a03d3af

	function installConsoleExtensions(commandLineApi) {
	if (commandLineApi.require) { return; }
	const { tryGetCwd } = require('internal/process/execution');
	const CJSModule = require('internal/modules/cjs/loader').Module;
	const { makeRequireFunction } = require('internal/modules/cjs/helpers');
	const consoleAPIModule = new CJSModule('<inspector console>');
	const cwd = tryGetCwd();
	consoleAPIModule.paths = ArrayPrototypeConcat(
	CJSModule._nodeModulePaths(cwd),
	CJSModule.globalPaths
	);
	commandLineApi.require = makeRequireFunction(consoleAPIModule);
	}

[Trott]

@nodejs/repl