Why is this package recommended to be a dependency instead of devDependency?

[TheWirv]

As the title says, is there any particular reason not to make prop-types a devDependency?

[ljharb]

Because it runs in your production code, even if React compiles out its propTypes checking in production. If you don't include prop-types in your app, PropTypes.oneOf() will throw an error, for example.

Dev deps are for things needed to develop a package, like babel/eslint/etc; regular deps are for things needed in/by your code, which includes propTypes.

[TheWirv]

Because it runs in your production code, even if React compiles out its propTypes checking in production. If you don't include prop-types in your app, PropTypes.oneOf() will throw an error, for example.

Dev deps are for things needed to develop a package, like babel/eslint/etc; regular deps are for things needed in/by your code, which includes propTypes.

Okay, thanks for the answer. The second part of that was already clear to me, but after having read the following, "... will check props passed to your components against those definitions, and warn in development if they don’t match," I didn't really expect it to run in production code.

[ljharb]

Fair enough :-) it's confusing because React doesn't warn on propTypes in production, but the propTypes themselves are still used.

[TheWirv]

Fair enough :-) it's confusing because React doesn't warn on propTypes in production, but the propTypes themselves are still used.

That makes sense :)

[joetidee]

Is three a way to keep prop-types enabled in production? I want to observe and report on prop-typ warnings against production data.

[ljharb]

I think you’d have to use the development build of react, with NODE_ENV not set to production.

[joetidee]

Would be great to make it a feature of the package, defaulting to production.

[ljharb]

That’s not within the power of this package - it’s defined within react itself.

[joetidee]

So, if the checking of the production value here was made optional, this still wouldn't expose prop-type warnings in production? https://github.com/facebook/prop-types/blob/b67bbd40b5bf8b27475801ecdb7617071ceaccac/index.js

[ljharb]

Yes, because React itself calls propTypes on components.

[joetidee]

Are you saying that react will not call propTypes in production?

Some.Component.propTypes = {
  foo: Proptypes.string.isRequired,
};

[ljharb]

Yes, that is precisely what I am saying.