Prerender error and workarounds

[thangngoc89]

Preact-cli comes with prerender which render your / route using server-side rendering technique. So if you run npm start successfully but npm run build produces some errors, this mean that the prerender is failing because of some code requires DOM to work.

Workarounds:

• Wrap your with this to make sure it won't execute when prerendering.

if (typeof window !== "undefined") {
  // Your code here
}

• Turn off preredering by run npm run build -- --no-prerender

[nephix]

Had the same issue using HashRouter. npm run build -- --prerender=false didn't work for me but the window !== "undefined" check did.

[thangngoc89]

@nephix I updated the command. So sorry. npm run build -- --no-prerender

[rkostrzewski]

@thangngoc89 what's expected outcome of this issue? Friendly error message with steps how to write code which could be used on node side?

I guess we could wrap prerender with try catch block that checks for TypeErrors (possibly with some whitelist of variables like window, document, location, localStorage and others) and prints user friendly message with steps on how to fix this.

[nephix]

IMO the example app that preact-cli creates should show how to handle the issue if DOM is required on /

[thangngoc89]

@rkostrzewski Yup. A friendly error for user.

[glegenty]

Hi !

I try to prerender the default template with no extra code but it fails.
i simple use npm run build and i got this :

Unable to read file: /Users/jorel/Projects/proto/prerender/src/external "preact"
Error: No valid exports main found for '/Users/jorel/Projects/proto/prerender/node_modules/preact'
method: HteQ
at: /Users/jorel/Projects/proto/prerender/src/external "preact":1:17

I'm on macOS Catalina with node 13.6.0

Did i miss something ?

[glegenty]

The issue was coming from node 13.6. I siwtched to 12.6.2 and the prerender is working fine. The only issue that i see now is that the home page seems to not be rendered. I cannot find the html file in the build folder.

[ForsakenHarmony]

You might want to update to the latest preact version, that should fix the first problem you had