Merge branch 'error-type'

examples/error_extensions.rs

@@ -4,6 +4,7 @@ extern crate thiserror;
 use actix_rt;
 use actix_web::{guard, web, App, HttpResponse, HttpServer};
 use async_graphql::http::{graphiql_source, playground_source, GQLRequest, GQLResponse};
+use async_graphql::ErrorExtensions;
 use async_graphql::*;
 use futures::TryFutureExt;
 use serde_json::json;
@@ -20,54 +21,87 @@ pub enum MyError {
     ErrorWithoutExtensions,
 }
 
-impl MyError {
-    fn extend_err(&self) -> serde_json::Value {
-        match self {
+impl ErrorExtensions for MyError {
+    // lets define our base extensions
+    fn extend(&self) -> FieldError {
+        let extensions = match self {
             MyError::NotFound => json!({"code": "NOT_FOUND"}),
             MyError::ServerError(reason) => json!({ "reason": reason }),
             MyError::ErrorWithoutExtensions => {
                 json!("This will be ignored since it does not represent an object.")
             }
-        }
-    }
-}
+        };
 
-fn get_my_error() -> std::result::Result<String, MyError> {
-    Err(MyError::ServerError("The database is locked".to_owned()))
+        FieldError(format!("{}", self), Some(extensions))
+    }
 }
 
 struct QueryRoot;
 
 #[Object]
 impl QueryRoot {
+    // It works on foreign types without extensions as before
     #[field]
-    async fn do_not_find(&self) -> FieldResult<i32> {
-        Err(MyError::NotFound).extend_err(MyError::extend_err)
+    async fn parse_without_extensions(&self) -> FieldResult<i32> {
+        Ok("234a".parse()?)
     }
 
+    // Foreign types can be extended
     #[field]
-    async fn fail(&self) -> FieldResult<String> {
-        Ok(get_my_error().extend_err(MyError::extend_err)?)
+    async fn parse_with_extensions(&self) -> FieldResult<i32> {
+        Ok("234a"
+            .parse()
+            .map_err(|e: std::num::ParseIntError| e.extend_with(|_| json!({"code": 404})))?)
     }
 
+    // THIS does unfortunately NOT work because ErrorExtensions is implemented for &E and not E.
+    // Which is necessary for the overwrite by the user.
+
+    //#[field]
+    // async fn parse_with_extensions_result(&self) -> FieldResult<i32> {
+    //    Ok("234a".parse().extend_err(|_| json!({"code": 404}))?)
+    // }
+
+    // Using our own types we can implement some base extensions
     #[field]
-    async fn without_extensions(&self) -> FieldResult<String> {
-        Err(MyError::ErrorWithoutExtensions).extend_err(MyError::extend_err)?
+    async fn extend(&self) -> FieldResult<i32> {
+        Err(MyError::NotFound.extend())?
     }
 
-    // Using the ResultExt trait, we can attach extensions on the fly capturing the execution
-    // environment. This method works on foreign types as well. The trait is implemented for all
-    // Results where the error variant implements `std::error::Error`.
+    // Or on the result
     #[field]
-    async fn parse_value(&self, val: String) -> FieldResult<i32> {
-        val.parse().extend_err(|err| {
-            json!({ "description": format!("Could not parse value '{}': {}", val, err) })
-        })
+    async fn extend_result(&self) -> FieldResult<i32> {
+        Err(MyError::NotFound).extend()?
     }
 
+    // Base extensions can be further extended
     #[field]
-    async fn parse_value2(&self, val: String) -> FieldResult<i32> {
-        Ok(val.parse()?)
+    async fn more_extensions(&self) -> FieldResult<String> {
+        // resolves to extensions: { "code": "NOT_FOUND", "reason": "my reason" }
+        Err(MyError::NotFound.extend_with(|_e| json!({"reason": "my reason"})))?
+    }
+
+    // works with results as well
+    #[field]
+    async fn more_extensions_on_result(&self) -> FieldResult<String> {
+        // resolves to extensions: { "code": "NOT_FOUND", "reason": "my reason" }
+        Err(MyError::NotFound).extend_err(|_e| json!({"reason": "my reason"}))?
+    }
+
+    // extend_with is chainable
+    #[field]
+    async fn chainable_extensions(&self) -> FieldResult<String> {
+        let err = MyError::NotFound
+            .extend_with(|_| json!({"ext1": 1}))
+            .extend_with(|_| json!({"ext2": 2}))
+            .extend_with(|_| json!({"ext3": 3}));
+        Err(err)?
+    }
+
+    // extend_with overwrites keys which are already present
+    #[field]
+    async fn overwrite(&self) -> FieldResult<String> {
+        Err(MyError::NotFound.extend_with(|_| json!({"code": "overwritten"})))?
     }
 }
 
@@ -96,6 +130,9 @@ async fn gql_graphiql() -> HttpResponse {
 
 #[actix_rt::main]
 async fn main() -> std::io::Result<()> {
+    println!("Playground: http://localhost:8000");
+    println!("Graphiql: http://localhost:8000/graphiql");
+
     HttpServer::new(move || {
         App::new()
             .data(Schema::new(QueryRoot, EmptyMutation, EmptySubscription))

src/error.rs

@@ -1,10 +1,10 @@
 use graphql_parser::query::{ParseError, Value};
 use graphql_parser::Pos;
-use std::error::Error as StdError;
 use std::fmt::Debug;
 
 /// FieldError type
-pub struct FieldError(anyhow::Error, Option<serde_json::Value>);
+#[derive(Clone, Debug)]
+pub struct FieldError(pub String, pub Option<serde_json::Value>);
 
 impl FieldError {
     #[doc(hidden)]
@@ -37,10 +37,52 @@ pub type FieldResult<T> = std::result::Result<T, FieldError>;
 
 impl<E> From<E> for FieldError
 where
-    E: StdError + Send + Sync + 'static,
+    E: std::fmt::Display + Send + Sync + 'static,
 {
     fn from(err: E) -> Self {
-        FieldError(anyhow::Error::from(err), None)
+        FieldError(format!("{}", err), None)
+    }
+}
+
+#[allow(missing_docs)]
+pub trait ErrorExtensions
+where
+    Self: Sized,
+{
+    fn extend(&self) -> FieldError;
+    fn extend_with<C>(self, cb: C) -> FieldError
+    where
+        C: FnOnce(&Self) -> serde_json::Value,
+    {
+        let name = self.extend().0;
+
+        if let Some(mut base) = self.extend().1 {
+            let mut cb_res = cb(&self);
+            if let Some(base_map) = base.as_object_mut() {
+                if let Some(cb_res_map) = cb_res.as_object_mut() {
+                    base_map.append(cb_res_map);
+                }
+                return FieldError(name, Some(serde_json::json!(base_map)));
+            } else {
+                return FieldError(name, Some(cb_res));
+            }
+        }
+
+        FieldError(name, Some(cb(&self)))
+    }
+}
+
+impl ErrorExtensions for FieldError {
+    fn extend(&self) -> FieldError {
+        self.clone()
+    }
+}
+
+// implementing for &E instead of E gives the user the possibility to implement for E which does
+// not conflict with this implementation acting as a fallback.
+impl<E: std::fmt::Display> ErrorExtensions for &E {
+    fn extend(&self) -> FieldError {
+        FieldError(format!("{}", self), None)
     }
 }
 
@@ -48,26 +90,33 @@ where
 pub trait ResultExt<T, E>
 where
     Self: Sized,
-    E: StdError + Send + Sync + 'static,
 {
     fn extend_err<CB>(self, cb: CB) -> FieldResult<T>
     where
         CB: FnOnce(&E) -> serde_json::Value;
+
+    fn extend(self) -> FieldResult<T>;
 }
 
+// This is implemented on E and not &E which means it cannot be used on foreign types.
+// (see example).
 impl<T, E> ResultExt<T, E> for std::result::Result<T, E>
 where
-    E: StdError + Send + Sync + 'static,
+    E: ErrorExtensions + Send + Sync + 'static,
 {
     fn extend_err<C>(self, cb: C) -> FieldResult<T>
     where
         C: FnOnce(&E) -> serde_json::Value,
     {
         match self {
-            Err(err) => {
-                let extended_err = cb(&err);
-                Err(FieldError(err.into(), Some(extended_err)))
-            }
+            Err(err) => Err(err.extend_with(|e| cb(e))),
+            Ok(value) => Ok(value),
+        }
+    }
+
+    fn extend(self) -> FieldResult<T> {
+        match self {
+            Err(err) => Err(err.extend()),
             Ok(value) => Ok(value),
         }
     }
@@ -204,7 +253,7 @@ pub enum QueryError {
 
     #[error("Failed to resolve field: {err}")]
     FieldError {
-        err: anyhow::Error,
+        err: String,
         extended_error: Option<serde_json::Value>,
     },
 }

src/http/mod.rs

@@ -121,6 +121,7 @@ impl<'a> Serialize for GQLError<'a> {
                     if let Some(obj @ serde_json::Value::Object(_)) = extended_error {
                         map.insert("extensions".to_string(), obj.clone());
                     }
+
                     seq.serialize_element(&serde_json::Value::Object(map))?;
                 } else {
                     seq.serialize_element(&serde_json::json!({
@@ -235,7 +236,7 @@ mod tests {
             },
             path: None,
             err: QueryError::FieldError {
-                err: anyhow::anyhow!("MyErrorMessage"),
+                err: "MyErrorMessage".to_owned(),
                 extended_error: Some(json!({
                     "code": "MY_TEST_CODE"
                 })),

src/lib.rs

@@ -100,7 +100,7 @@ pub mod http;
 
 pub use base::{Scalar, Type};
 pub use context::{Context, QueryPathSegment, Variables};
-pub use error::{Error, FieldError, FieldResult, QueryError, ResultExt};
+pub use error::{Error, ErrorExtensions, FieldError, FieldResult, QueryError, ResultExt};
 pub use graphql_parser::query::Value;
 pub use graphql_parser::Pos;
 pub use query::{QueryBuilder, QueryResponse};