Include errors along side successful components in BRP bevy/get method (#15516)

## Objective

I am using BRP for a web inspector. To get components from a entity is
first do a `bevy/list` on the specific entity and then use the result in
a `bevy/get` request. The problem with this is `bevy/list` returns all
components even if they aren't reflect-able (which is what I expect) but
when I then do a `bevy/get` request even if all bar one of the
components are reflect-able the request will fail.

## Solution

Update the `bevy/get` response to include a map of components like it
did for successful request and a map of errors. This means if one or
more components are not present on the entity or cannot be reflected it
will not fail the entire request.

I also only did `bevy/get` as I don't think any of the other methods
would benefit from this.

## Testing

I tested this with my inspector and with a http client and it worked as
expected.

---------

Co-authored-by: Pablo Reinhardt <126117294+pablo-lua@users.noreply.github.com>

crates/bevy_remote/src/builtin_methods.rs

@@ -18,7 +18,7 @@ use bevy_reflect::{
 };
 use bevy_utils::HashMap;
 use serde::{de::DeserializeSeed as _, Deserialize, Serialize};
-use serde_json::Value;
+use serde_json::{Map, Value};
 
 use crate::{error_codes, BrpError, BrpResult};
 
@@ -64,6 +64,11 @@ pub struct BrpGetParams {
     ///
     /// [full paths]: bevy_reflect::TypePath::type_path
     pub components: Vec<String>,
+
+    /// An optional flag to fail when encountering an invalid component rather
+    /// than skipping it. Defaults to false.
+    #[serde(default)]
+    pub strict: bool,
 }
 
 /// `bevy/query`: Performs a query over components in the ECS, returning entities
@@ -228,7 +233,20 @@ pub struct BrpSpawnResponse {
 }
 
 /// The response to a `bevy/get` request.
-pub type BrpGetResponse = HashMap<String, Value>;
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(untagged)]
+pub enum BrpGetResponse {
+    /// The non-strict response that reports errors separately without failing the entire request.
+    Lenient {
+        /// A map of successful components with their values.
+        components: HashMap<String, Value>,
+        /// A map of unsuccessful components with their errors.
+        errors: HashMap<String, Value>,
+    },
+    /// The strict response that will fail if any components are not present or aren't
+    /// reflect-able.
+    Strict(HashMap<String, Value>),
+}
 
 /// The response to a `bevy/list` request.
 pub type BrpListResponse = Vec<String>;
@@ -273,26 +291,65 @@ fn parse_some<T: for<'de> Deserialize<'de>>(value: Option<Value>) -> Result<T, B
 
 /// Handles a `bevy/get` request coming from a client.
 pub fn process_remote_get_request(In(params): In<Option<Value>>, world: &World) -> BrpResult {
-    let BrpGetParams { entity, components } = parse_some(params)?;
+    let BrpGetParams {
+        entity,
+        components,
+        strict,
+    } = parse_some(params)?;
 
     let app_type_registry = world.resource::<AppTypeRegistry>();
     let type_registry = app_type_registry.read();
     let entity_ref = get_entity(world, entity)?;
 
-    let mut response = BrpGetResponse::default();
+    let mut response = if strict {
+        BrpGetResponse::Strict(Default::default())
+    } else {
+        BrpGetResponse::Lenient {
+            components: Default::default(),
+            errors: Default::default(),
+        }
+    };
 
     for component_path in components {
-        let reflect_component = get_reflect_component(&type_registry, &component_path)
-            .map_err(BrpError::component_error)?;
+        match handle_get_component(&component_path, entity, entity_ref, &type_registry) {
+            Ok(serialized_object) => match response {
+                BrpGetResponse::Strict(ref mut components)
+                | BrpGetResponse::Lenient {
+                    ref mut components, ..
+                } => {
+                    components.extend(serialized_object.into_iter());
+                }
+            },
+            Err(err) => match response {
+                BrpGetResponse::Strict(_) => return Err(err),
+                BrpGetResponse::Lenient { ref mut errors, .. } => {
+                    let err_value = serde_json::to_value(err).map_err(BrpError::internal)?;
+                    errors.insert(component_path, err_value);
+                }
+            },
+        }
+    }
+
+    serde_json::to_value(response).map_err(BrpError::internal)
+}
+
+/// Handle a single component for [`process_remote_get_request`].
+fn handle_get_component(
+    component_path: &str,
+    entity: Entity,
+    entity_ref: EntityRef,
+    type_registry: &TypeRegistry,
+) -> Result<Map<String, Value>, BrpError> {
+    let reflect_component =
+        get_reflect_component(type_registry, component_path).map_err(BrpError::component_error)?;
 
     // Retrieve the reflected value for the given specified component on the given entity.
     let Some(reflected) = reflect_component.reflect(entity_ref) else {
-            return Err(BrpError::component_not_present(&component_path, entity));
+        return Err(BrpError::component_not_present(component_path, entity));
     };
 
     // Each component value serializes to a map with a single entry.
-        let reflect_serializer =
-            ReflectSerializer::new(reflected.as_partial_reflect(), &type_registry);
+    let reflect_serializer = ReflectSerializer::new(reflected.as_partial_reflect(), type_registry);
     let Value::Object(serialized_object) =
         serde_json::to_value(&reflect_serializer).map_err(|err| BrpError {
             code: error_codes::COMPONENT_ERROR,
@@ -307,10 +364,7 @@ pub fn process_remote_get_request(In(params): In<Option<Value>>, world: &World)
         });
     };
 
-        response.extend(serialized_object.into_iter());
-    }
-
-    serde_json::to_value(response).map_err(BrpError::internal)
+    Ok(serialized_object)
 }
 
 /// Handles a `bevy/query` request coming from a client.

crates/bevy_remote/src/lib.rs

@@ -109,6 +109,17 @@
 //! `params`:
 //! - `entity`: The ID of the entity whose components will be fetched.
 //! - `components`: An array of [fully-qualified type names] of components to fetch.
+//! - `strict` (optional): A flag to enable strict mode which will fail if any one of the
+//!   components is not present or can not be reflected. Defaults to false.
+//!
+//! If `strict` is false:
+//!
+//! `result`:
+//! - `components`: A map associating each type name to its value on the requested entity.
+//! - `errors`: A map associating each type name with an error if it was not on the entity
+//!   or could not be reflected.
+//!
+//! If `strict` is true:
 //!
 //! `result`: A map associating each type name to its value on the requested entity.
 //!