50009b66ce
This completely overhauls the error system used in async-graphql. - `Error` has been renamed to `ServerError` and `FieldError` has been renamed to just `Error`. This is because `FieldError` is by far the most common error that users will have to use so it makes sense to use the most obvious error name. Also, the current name didn't make sense as it was used for things other than field errors, such as the data callback for websockets. - `ServerError` has been made completely opaque. Before it was an enum of all the possible errors, but now it just contains an error message, the locations, the path and extensions. It is a shame that we lose information, it makes more sense as _conceptually_ GraphQL does not provide that information. It also frees us to change the internals of async-graphql a lot more. - The path of errors is no longer an opaque JSON value but a regular type, `Vec<PathSegment>`. The type duplication of `PathSegment` and `QueryPathSegment` is unfortunate, I plan to work on this in the future. - Now that `ServerError` is opaque, `RuleError` has been removed from the public API, making it simpler. - Additionally `QueryError` has been completely removed. Instead the error messages are constructed ad-hoc; I took care to never repeat an error message. - Instead of constructing field-not-found errors inside the implementations of field resolvers they now return `Option`s, where a `None` value is representative of the field not being found. - As an unfortunate consequence of the last change, self-referential types based on the output of a subscription resolver can no longer be created. This does not mean anything for users, but causes lifetime issues in the implementation of merged objects. I fixed it with a bit of a hack, but this'll have to be looked into further. - `InputValueError` now has a generic parameter - it's kind of weird but it's necessary for ergonomics. It also improves error messages. - The `ErrorExtensions` trait has been removed. I didn't think the `extend` method was necessary since `From` impls exist. But the ergonomics are still there with a new trait `ExtendError`, which is implemented for both errors and results. - `Response` now supports serializing multiple errors. This allows for nice things like having multiple validation errors not be awkwardly shoved into a single error. - When an error occurs in execution, data is sent as `null`. This is slightly more compliant with the spec but the algorithm described in <https://spec.graphql.org/June2018/#sec-Errors-and-Non-Nullability> has yet to be implemented.
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Query and Mutation
Query root object
The query root object is a GraphQL object with a definition similar to other objects. Resolver functions for all fields of the query object are executed concurrently.
use async_graphql::*;
struct Query;
#[Object]
impl Query {
async fn user(&self, username: String) -> Result<Option<User>> {
// Look up users from the database
}
}
Mutation root object
The mutation root object is also a GraphQL object, but it executes sequentially. One mutation following from another will only be executed only after the first mutation is completed.
The following mutation root object provides an example of user registration and login:
use async_graphql::*;
struct Mutation;
#[Object]
impl Mutation {
async fn signup(&self, username: String, password: String) -> Result<bool> {
// User signup
}
async fn login(&self, username: String, password: String) -> Result<String> {
// User login (generate token)
}
}