Codama ➤ Errors

This package defines a CodamaError class that accepts a specific error code and a context object based on that code. It enables us to catch and handle errors in a more structured way.

Installation

pnpm install @codama/errors

[!NOTE] This package is included in the main codama package. Meaning, you already have access to its content if you are installing Codama this way.

pnpm install codama

Reading error messages

In development mode

When the NODE_ENV environment variable is not set to "production", every error message will be included in the bundle. As such, you will be able to read them in plain language wherever they appear.

In production mode

On the other hand, when NODE_ENV is set to "production", error messages will be stripped from the bundle to save space. Only the error code will appear when an error is encountered. Follow the instructions in the error message to convert the error code back to the human-readable error message.

For instance, to recover the error text for the error with code 123:

npx @codama/errors decode -- 123

Catching errors

When you catch a CodamaError and assert its error code using isCodamaError(), TypeScript will refine the error's context to the type associated with that error code. You can use that context to render useful error messages, or to make context-aware decisions that help your application to recover from the error.

import { CODAMA_ERROR__UNEXPECTED_NODE_KIND, isCodamaError } from '@codama/errors';

try {
    const codama = createFromJson(jsonIdl);
} catch (e) {
    if (isCodamaError(e, CODAMA_ERROR__UNEXPECTED_NODE_KIND)) {
        const { expectedKinds, kind, node } = e.context;
        // ...
    } else if (isCodamaError(e, CODAMA_ERROR__VERSION_MISMATCH)) {
        const { codamaVersion, rootVersion } = e.context;
        // ...
    } else {
        throw e;
    }
}

Contributing

Adding a new error

To add a new error in Codama, follow these steps:

1. Add a new exported error code constant to src/codes.ts. Find the most appropriate group for your error and ensure it is appended to the end of that group.
2. Add that new constant to the CodamaErrorCode union in src/codes.ts.
3. If you would like the new error to encapsulate context about the error itself define that context in src/context.ts.
4. Add the error's message to src/messages.ts. Any context values that you defined above will be interpolated into the message wherever you write $key, where key is the index of a value in the context (eg. 'Unrecognized node `$kind`.').
5. Publish a new version of @codama/errors using changesets — maintainers will handle this via tha changesets CI workflow.
6. Bump the version of @codama/errors or codama in the consumer package from which the error is thrown.

Removing an error message

• Don't remove errors.
• Don't change the meaning of an error message.
• Don't change or reorder error codes.
• Don't change or remove members of an error's context.

When an older client throws an error, we want to make sure that they can always decode the error. If you make any of the changes above, old clients will, by definition, not have received your changes. This could make the errors that they throw impossible to decode going forward.