Node.js + sourcemaps = incorrect code positions in Sentry

[o2genum]

Package + Version

• @sentry/browser 4.5.3
• @sentry/node 4.5.3
• raven-js

Description

This is more of an issue with Node.js, I guess Sentry for Node should handle in some way.

Node.js wraps source files in an IIFE. A simple example:

And I know why: Node.js wraps javascript sources in an IIFE. This shifts the first line of the file by the length of the wrapper. For example:

example.js
throw new Error("Hello!")

Now run node example.js:

C:\Users\user\Desktop>node example.js
C:\Users\user\Desktop\example.js:1
(function (exports, require, module, __filename, __dirname) { throw new Error("Hello!")
                                                              ^
Error: Hello!
    at Object.<anonymous> (C:\Users\user\Desktop\example.js:1:69)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:742:12)
    at startup (internal/bootstrap/node.js:279:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:752:3)

This wrapper shifts the first line of every source file, making stacktrace column positions for the first line incorrect. Which in its turn breaks minified code + Sentry sourcemap processing, and code positions in Sentry are not even close.

I wonder what can be done about this?

[kamilogorek]

Do you have a repro-case I can use to debug this? I tested source maps quite a lot of time in Sentry using Node and it worked just fine.

[o2genum]

Ok, here is the repo that reproduces the issue (needs Sentry credentials for testing):
https://github.com/o2genum/node-stacktrace-issue-reproduce
And the error: https://sentry.io/share/issue/c3961143a9ee4c6fb796d773217f0169/

I think most users don't have this issue because of non-removable comments like this:

/*!
 * @overview es6-promise - a tiny implementation of Promises/A+.
 * @copyright Copyright (c) 2014 Yehuda Katz, Tom Dale, Stefan Penner and contributors (Conversion to ES6 API by Jake Archibald)
 * @license   Licensed under MIT license
 *            See https://raw.githubusercontent.com/stefanpenner/es6-promise/master/LICENSE
 * @version   v4.2.5+7f2b526d
 */

These comments get into the minified file, cutting it with newlines. I turned off bundling of external modules in the Webpack config, so I don't get these comments from various modules in my bundle.

[kamilogorek]

Changes required for your repro to work:

• remove nodeExernals from externals, as it's meant to be run in node env
• add integrations: [new Sentry.Integrations.RewriteFrames()] to your Sentry.init call
• change include: ['.'] to include: ['./build'] in your webpack config

https://docs.sentry.io/platforms/node/sourcemaps/#updating-sentry-sdk-configuration-to-support-source-maps

Also because you are using windows locally, you may want to look at this comment – #1857 (comment)

(dsn are public, so no need to hide it on my screen :p)

[kamilogorek]

Closing due to inactivity

[o2genum]

I got this working in my Electron app with @sentry/electron.
I had to do some configuration and some hacking, though.

So again, I have a main bundle + an external module, both minified.

• I used include: ['.'], this made Sentry match paths properly. Plus ignoreFile: '.sentryignore' to control what to upload to Sentry.
• As for my external module in node_modules/my_external_module (which is very hard to build into the main bundle), I include it in .sentryignore.
• My my_external_module is a local package, so I had to use yarn, because npm symlinks local dependencies, not copies them, and @sentry/webpack-plugin does not follow symlinks on Windows. This way, my_external_module's sourcemaps and sources are uploaded to Sentry too.
• I still had to force a newline in the beginning of the minified files. Both for the main bundle and my_external_module. With PreamblePlugin in Webpack, and preamble option in Rollup. Node.js indeed wraps sources that it loads with an IIFE. I still think this may cause problems in rare cases, when the minified file is not cut with /*! License */ comments of the bundled dependencies, and all errors thus occur on the first line.

[kamilogorek]

Thanks for the detailed response @o2genum, appreciate it!