[RFC] Codemod invariant -> throw new Error #22435

When this code was written, the error codes map (`codes.json`) was created on-the-fly, so we had to lazily require from inside the visitor. Because `codes.json` is now checked into source, we can import it a single time in module scope.

We use a script to minify our error messages in production. Each message is assigned an error code, defined in `scripts/error-codes/codes.json`. Then our build script replaces the messages with a link to our error decoder page, e.g. https://reactjs.org/docs/error-decoder.html/?invariant=92 This enables us to write helpful error messages without increasing the bundle size. Right now, the script only works for `invariant` calls. It does not work if you throw an Error object. This is an old Facebookism that we don't really need, other than the fact that our error minification script relies on it. So, I've updated the script to minify error constructors, too: Input: Error(`A ${adj} message that contains ${noun}`); Output: Error(formatProdErrorMessage(ERR_CODE, adj, noun)); It only works for constructors that are literally named Error, though we could add support for other names, too. As a next step, I will add a lint rule to enforce that errors written this way must have a corresponding error code.

This error message wasn't being minified because it doesn't use invariant. The reason it didn't use invariant is because this particular error is created without begin thrown — it doesn't need to be thrown because it's located inside the error handling part of the runtime. Now that the error minification script supports Error constructors, we can minify it by assigning it a production error code in `scripts/error-codes/codes.json`. To support the use of Error constructors more generally, I will add a lint rule that enforces each message has a corresponding error code.

Adds a lint rule that detects when an Error constructor is used without a corresponding production error code. We already have this for `invariant`, but not for regular errors, i.e. `throw new Error(msg)`. There's also nothing that enforces the use of `invariant` besides convention. There are some packages where we don't care to minify errors. These are packages that run in environments where bundle size is not a concern, like react-pg. I added an override in the ESLint config to ignore these.

I'm adding this codemod to the repo temporarily, but I'll revert it in the same PR. That way we don't have to check it in but it's still accessible (via the PR) if we need it later.

This commit contains only automated changes: npx jscodeshift -t scripts/codemod-invariant.js packages --ignore-pattern="node_modules/**/*" yarn linc --fix yarn prettier I will do any manual touch ups in separate commits so they're easier to review.

This reverts the codemod script and ESLint config I added temporarily in order to perform the invariant codemod.

A few manual changes I made after the codemod ran.

Currently we're not consistent about which packages should have their errors minified in production and which ones should. This adds a field to the bundle configuration to control whether to apply the transform. We should decide what the criteria is going forward. I think it's probably a good idea to minify any package that gets sent over the network. So yes to modules that run in the browser, and no to modules that run on the server and during development only.

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

[RFC] Codemod invariant -> throw new Error #22435

[RFC] Codemod invariant -> throw new Error #22435

Commits on Sep 30, 2021