Fix for '[HMR] You need to restart the application!' on server sided error

[Bram-Zijp]

When you make an error (e.g. undefined variable) somewhere in the server.js, you need to restart the application. To prevent this you should only restart the server when there's no errors.

[gregmartyn]

It's not working for me. What reliably breaks HMR for me is a syntax error. E.g. put [[[[[[[[[ somewhere in one of your files.

nodejs_1 | [7:23:02 PM] Compiling server
nodejs_1 | [7:23:02 PM] Compiled server in 178ms
nodejs_1 | [HMR] Cannot apply update.
nodejs_1 | [HMR] Error: Module build failed (from ./razzle/packages/razzle/node_modules/babel-loader/lib/index.js):
nodejs_1 | SyntaxError: Unexpected token (45:0)

After that, even with this patch, I'll see stuff like this in the log:
nodejs_1 | [7:23:18 PM] Compiling client
nodejs_1 | [7:23:18 PM] Compiling server
nodejs_1 | [7:23:18 PM] Compiled server in 477ms
nodejs_1 | [7:23:18 PM] Compiled client in 479ms
nodejs_1 | [7:23:19 PM] Compiling client
nodejs_1 | [7:23:19 PM] Compiled client in 671ms
nodejs_1 | [7:23:26 PM] Compiling server
nodejs_1 | [7:23:31 PM] Compiled server in 5s

but never
nodejs_1 | [HMR] Update applied.

[jaredpalmer]

@crosscompile does this happen to us too?

cc @TheLarkInn any ideas about what would break HMR ?

[Bram-Zijp]

Note: This is for server sided errors only.
Try generate an error in the server.js file. With a fresh Razzle project it will log the [HMR] You need to restart the application! message

In the following stack trace I imported a test.js file in the server.js file. Then I added an undefined variable.

√ success server compiled in 270ms
✅  Server-side HMR Enabled!
🚀 started
√ success server compiled in 64ms
🔁  HMR Reloading `./server/server.js`...
[HMR] Cannot apply update.
[HMR] ReferenceError: asdfasdf is not defined
    at Module../src/server/test.js (A:\razzle-example\build\webpack:\src\server\test.js:1:1)
    at __webpack_require__ (A:\razzle-example\build\webpack:\webpack\bootstrap:682:1)
    at fn (A:\razzle-example\build\webpack:\webpack\bootstrap:59:1)
    at Module../src/server/server.js (A:\razzle-example\build\server.js:1097:63)
    at __webpack_require__ (A:\razzle-example\build\webpack:\webpack\bootstrap:682:1)
    at fn (A:\razzle-example\build\webpack:\webpack\bootstrap:59:1)
    at A:\razzle-example\build\webpack:\src\index.js:34:1
    at A:\razzle-example\build\webpack:\src\index.js:38:1
    at hotApply (A:\razzle-example\build\webpack:\webpack\bootstrap:590:1)
    at A:\razzle-example\build\webpack:\webpack\bootstrap:272:1
[HMR] You need to restart the application!

[gregmartyn]

ReferenceError and SyntaxError both block HMR for me on the server-side, with and without this patch. I never end up in the catch()

[Bram-Zijp]

My bad. I didn't include the whole solution. It should work now.

[jaredpalmer]

Cool

[gregmartyn]

@jaredpalmer did this actually work for you? It didn't make a difference for me. HMR was erroring before it called module.hot.accept

[jaredpalmer]

@crosscompile is investigating this today.

[jackjocross]

This is working for me locally, nice stuff @Bram-Zijp!

@gregmartyn are you sure you have the entire patch? Initially I missed changing the server import to a require and for some reason that allows the server to reload.

let app = require('./server').default;

[gregmartyn]

I did something similar. Tried again and it's working. Thanks!