This PR implements the first version of a suggested unification (and
documentation) of the errors that we return from the API today.
The goal is for this to be the first step towards the error type defined
in this internal [linear
task](https://linear.app/unleash/issue/1-629/define-the-error-type
'Define the new API error type').
## The state of things today
As things stand, we currently have no (or **very** little) documentation
of the errors that are returned from the API. We mention error codes,
but never what the errors may contain.
Second, there is no specified format for errors, so what they return is
arbitrary, and based on ... Who knows? As a result, we have multiple
different errors returned by the API depending on what operation you're
trying to do. What's more, with OpenAPI validation in the mix, it's
absolutely possible for you to get two completely different error
objects for operations to the same endpoint.
Third, the errors we do return are usually pretty vague and don't really
provide any real help to the user. "You don't have the right
permissions". Great. Well what permissions do I need? And how would I
know? "BadDataError". Sick. Why is it bad?
... You get it.
## What we want to achieve
The ultimate goal is for error messages to serve both humans and
machines. When the user provides bad data, we should tell them what
parts of the data are bad and what they can do to fix it. When they
don't have the right permissions, we should tell them what permissions
they need.
Additionally, it would be nice if we could provide an ID for each error
instance, so that you (or an admin) can look through the logs and locate
he incident.
## What's included in **this** PR?
This PR does not aim to implement everything above. It's not intended to
magically fix everything. Its goal is to implement the necessary
**breaking** changes, so that they can be included in v5. Changing error
messages is a slightly grayer area than changing APIs directly, but
changing the format is definitely something I'd consider breaking.
So this PR:
- defines a minimal version of the error type defined in the [API error
definition linear
task](https://linear.app/unleash/issue/1-629/define-the-error-type).
- aims to catch all errors we return today and wrap them in the error
type
- updates tests to match the new expectations.
An important point: because we are cutting v5 very soon and because work
for this wasn't started until last week, the code here isn't necessarily
very polished. But it doesn't need to be. The internals can be as messy
as we want, as long as the API surface is stable.
That said, I'm very open to feedback about design and code completeness,
etc, but this has intentionally been done quickly.
Please also see my inline comments on the changes for more specific
details.
### Proposed follow-ups
As mentioned, this is the first step to implementing the error type. The
public API error type only exposes `id`, `name`, and `message`. This is
barely any more than most of the previous messages, but they are now all
using the same format. Any additional properties, such as `suggestion`,
`help`, `documentationLink` etc can be added as features without
breaking the current format. This is an intentional limitation of this
PR.
Regarding additional properties: there are some error responses that
must contain extra properties. Some of these are documented in the types
of the new error constructor, but not all. This includes `path` and
`type` properties on 401 errors, `details` on validation errors, and
more.
Also, because it was put together quickly, I don't yet know exactly how
we (as developers) would **prefer** to use these new error messages
within the code, so the internal API (the new type, name, etc), is just
a suggestion. This can evolve naturally over time if (based on feedback
and experience) without changing the public API.
## Returning multiple errors
Most of the time when we return errors today, we only return a single
error (even if many things are wrong). AJV, the OpenAPI integration we
use does have a setting that allows it to return all errors in a request
instead of a single one. I suggest we turn that on, but that we do it in
a separate PR (because it updates a number of other snapshots).
When returning errors that point to `details`, the objects in the
`details` now contain a new `description` property. This "deprecates"
the `message` property. Due to our general deprecation policy, this
should be kept around for another full major and can be removed in v6.
```json
{
"name": "BadDataError",
"message": "Something went wrong. Check the `details` property for more information."
"details": [{
"message": "The .params property must be an object. You provided an array.",
"description": "The .params property must be an object. You provided an array.",
}]
}
```
