Crash on 7.0.0-canary.0, production build

[dmitweb]

Bug report

Describe the bug

Production build. Sometimes when reload page, app crashes.
"var r" undefined on 1 screenshot

To Reproduce

Steps to reproduce the behavior, please provide code snippets or a repository:

1. Reload page, or go to some page
2. See error

Expected behavior

Page without errors

Screenshots

System information

• OS: Linux
• Version of Next.js: 7.0.0-canary.0

Additional context

Error does not always occur, sometimes everything works as usual.

[timneutkens]

Reload page, or go to some page

This is not a good reproduction. A good reproduction is a minimal example, with code, preferable a GitHub repository. Based on the steps you're providing there is no way to reproduce the issue you're having.

[dmitweb]

@timneutkens yes, sorry for bad reproduction, i will try make example with error as fast as i can
i will attach 2 additional screenshots, in dev

[timneutkens]

I can't really do anything with the screenshots. I need a full reproduction.

[dmitweb]

When I looked more closely, similar to: #4927. For me really hard reproduce this issue on example "with-next-css". I needed to do a lot of browser page updates (on project, not on example). However, perhaps I found useful information.

// "dll-reference dll_a77a75e478981c1e0d25":
/!!
! external "dll_a77a75e478981c1e0d25" !
*/
/! no static exports found /
/*/ (function(module, exports) {

console.log(dll_a77a75e478981c1e0d25);

module.exports = dll_a77a75e478981c1e0d25;

/***/ })

},[[1,"static/runtime/webpack.js","styles"]]])
console.log(comp); return { page: comp.default }
})

As u can see i add 2 console.log.
"comp" not always exists. When I catch an error, "dll_a77a75e478981c1e0d25" is always undefined.
Also i add 2 screenshots, with error, and without.
On 1 screenshot we don't have error and console.log show us 2 Module.
On 2 screenshot we have error and console.log show us 1 undefined, and 1 Module.
@timneutkens Pay attention to the order of page loading.
With error we have _app, then page.
Without error we have page, then _app.

[dmitweb]

When i disabled AutoDllPlugin:
Error was not caught TypeError: Cannot read property 'default' of undefined at _app.tsx:218

_app.tsx:218
export default MyApp;

Error throwed in _app, don't know why, but seems sometimes export default _app is undefined.

[timneutkens]

Once again, I need a full reproduction. I'm sorry but I really can't help otherwise as it's impossible to debug comments.

[kachkaev]

@dmitweb are you using next-css plugin? If so, you might be facing vercel/next-plugins#244

[dmitweb]

@kachkaev yes, u are right. I checked prod build and found chunk with content:
(window.webpackJsonp=window.webpackJsonp||[]).push([[22],{772:function(n,o,c){},774:function(n,o,c){},776:function(n,o,c){},778:function(n,o,c){},780:function(n,o,c){}}]);
Thanks @kachkaev. I make repo @timneutkens with issue reproduction: https://github.com/dmitweb/next-css-crash-app
P.S. Maybe u need reload page 1-10 times

[timneutkens]

PR open to fix this: #5115