gatsby's error catching development code found in production

[pindjur]

I found bunch of error checks and messages in gatsby production build coming from app-[hash].js
Can we remove this like React did in their production code?
I tried to contribute but im still begginer.
If this is a feature, can it be disabled through env variables?
We dont debug production code but if we do could it will be possible to debug via source maps without error checks in app-[hash].js?

[LekoArts]

Hi, please follow our issue template as otherwise we don't understand what you're asking and thus we can't help you.

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## Description

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[pindjur]

Description

There is unnecessary code in production build generated by gatsby

Steps to reproduce

run gatsby build and gastby serve in gatsby starter default project root folder.
Open developer tools and go to sources panel.
open app.js
here is hosted gatsby starter default script at the time of writing
https://gatsby-starter-default-demo.netlify.app/app-812755817ebf00dbab64.js

Expected result

There should'n be error throwing and checking for error throwing

Actual result

there is 50 + error messages, even for PropTypes which is used only in development.
one of them are:
"var u=new Error("Calling PropTypes validators directly is not supported by the prop-types package. Use PropTypes.checkPropTypes() to call them. Read more at http://fb.me/use-check-prop-types");"

""

[pieh]

Ok few notes:

prop-types specific: we do use https://www.npmjs.com/package/babel-plugin-transform-react-remove-prop-types but it tuns out it doesn't handle some cases (including ones we pack by default):

Cases that it can't handle is when you set propTypes on component that is wrapped with React.forwardRef (like our gatsby-link). I would expect similar thing happening with React.memo (but not confirmed that yet). I will be creating reproduction and creating issue in its repository of plugin about this.

In any case - in production shimed version is used (which is pretty much just this https://github.com/facebook/prop-types/blob/master/factoryWithThrowingShims.js and this does include the warning you mentioned).

But let's make a list of thing that are in default starter bundles and see which ones we actually can fix:

Ones that actually originate from gatsby (and not from some dependencies) and we can drop:

• gatsby/packages/gatsby/cache-dir/gatsby-browser-entry.js

  Lines 64 to 71 in b24d802

  	if (isNaN(Number(query))) {
  	throw new Error(`useStaticQuery was called with a string but expects to be called using \`graphql\`. Try this:
  	import { useStaticQuery, graphql } from 'gatsby';
  	useStaticQuery(graphql\`${query}\`);
  	`)
  	}

  
  For this we can add process.env.NODE_ENV === `development` (similar to error we have a bit above it) to remove it from production (builds will fail anyway before we reach this stage)

• gatsby/packages/gatsby/cache-dir/gatsby-browser-entry.js

  Lines 75 to 81 in b24d802

  	} else {
  	throw new Error(
  	`The result of this StaticQuery could not be fetched.\n\n` +
  	`This is likely a bug in Gatsby and if refreshing the page does not fix it, ` +
  	`please open an issue in https://github.com/gatsbyjs/gatsby/issues`
  	)
  	}

  
  similarly - we can wrap it as well as we don't actually use this function in production (it get's replaced)

We for sure can't really touch react-dom ones:

• Minified exception occurred; use the non-minified dev environment for the full error message and additional helpful warnings. for example

There few coming from @reach/router ( https://github.com/reach/router/blob/1f26ef04fce873a78c6a4c4605b6c1ec29bea7a8/src/index.js#L526-L578 )

Few coming from react-side-effect (dependency of react-helmet) - https://github.com/gaearon/react-side-effect/blob/f1e020719f5cc429b96b260cab80ed51b63421a5/src/index.js#L14-L22

There are few cases of error we throw, but they are actually meant specifically for production code in lot of cases as well.

[LekoArts]

Closing this as stale since in the meantime Gatsby v4 and updated related packages were released. Please try with the latest versions and if you still see this problem open a new bug report (it must include a minimal reproduction).