Fix missing_debug_implementations in Xilem Core (#739)

This also updates to use `core::error::Error` now that it is stable.

Author: DJMcNab

xilem/src/driver.rs

@@ -52,8 +52,12 @@ impl RawProxy for MasonryProxy {
             }
         }
     }
+    fn dyn_debug(&self) -> &dyn std::fmt::Debug {
+        self
+    }
 }
 
+#[derive(Debug)]
 pub struct MasonryProxy(pub(crate) EventLoopProxy);
 
 impl MasonryProxy {

xilem_core/src/any_view.rs

@@ -166,6 +166,7 @@ where
 /// The state used by [`AnyView`].
 #[doc(hidden)]
 #[allow(unnameable_types)] // reason: Implementation detail, public because of trait visibility rules
+#[derive(Debug)]
 pub struct AnyViewState {
     inner_state: Box<dyn Any>,
     /// The generation is the value which is shown

xilem_core/src/deferred.rs

@@ -3,7 +3,7 @@
 
 use alloc::boxed::Box;
 use alloc::sync::Arc;
-use core::fmt::Display;
+use core::fmt::{Debug, Display};
 use core::marker::PhantomData;
 
 use crate::{DynMessage, Message, NoElement, View, ViewId, ViewPathTracker};
@@ -47,9 +47,18 @@ pub trait RawProxy<Message = DynMessage>: Send + Sync + 'static {
     //
     // e.g. an `Option<Arc<dyn FnMut(ProxyError, ProxyMessageId?)>>`?
     fn send_message(&self, path: Arc<[ViewId]>, message: Message) -> Result<(), ProxyError>;
+    /// Get the debug formatter for this proxy type.
+    fn dyn_debug(&self) -> &dyn Debug;
+}
+
+impl<Message: 'static> Debug for dyn RawProxy<Message> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        self.dyn_debug().fmt(f)
+    }
 }
 
 /// A way to send a message of an expected type to a specific view.
+#[derive(Debug)]
 pub struct MessageProxy<M: Message> {
     proxy: Arc<dyn RawProxy<DynMessage>>,
     path: Arc<[ViewId]>,
@@ -109,10 +118,8 @@ pub enum ProxyError {
     ///
     /// This likely requires async error handling to happen.
     ViewExpired(DynMessage, Arc<[ViewId]>),
-    #[allow(missing_docs)]
-    Other(&'static str),
-    // TODO: When core::error::Error is stabilised
-    // Other(Box<dyn core::error::Error + Send>),
+    /// An error specific to the driver being used.
+    Other(Box<dyn core::error::Error + Send>),
 }
 
 // Is it fine to use thiserror in this crate?
@@ -123,17 +130,16 @@ impl Display for ProxyError {
             ProxyError::ViewExpired(_, _) => {
                 f.write_fmt(format_args!("the corresponding view is no longer present"))
             }
-
-            ProxyError::Other(inner) => inner.fmt(f),
+            ProxyError::Other(inner) => Display::fmt(inner, f),
         }
     }
 }
 
-// impl std::error::Error for ProxyError {
-//     fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-//         match self {
-//             ProxyError::Other(inner) => inner.source(),
-//             _ => None,
-//         }
-//     }
-// }
+impl core::error::Error for ProxyError {
+    fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
+        match self {
+            ProxyError::Other(inner) => inner.source(),
+            _ => None,
+        }
+    }
+}

xilem_core/src/docs.rs

@@ -38,6 +38,7 @@
 use crate::{run_once, View, ViewPathTracker};
 
 /// A type used for documentation
+#[derive(Debug)]
 pub enum Fake {}
 
 impl ViewPathTracker for Fake {
@@ -63,6 +64,7 @@ pub trait DocsView<State, Action = ()>: View<State, Action, Fake> {}
 impl<V, State, Action> DocsView<State, Action> for V where V: View<State, Action, Fake> {}
 
 /// A state type usable in a component
+#[derive(Debug)]
 pub struct State;
 
 /// A minimal component.

xilem_core/src/element.rs

@@ -87,6 +87,7 @@ where
 /// correct `State` and `Action` types), as they do not need to actually add an element to the sequence.
 ///
 /// These views can also as the `alongside_view` in [`fork`](crate::fork).
+#[derive(Debug)]
 pub struct NoElement;
 
 impl ViewElement for NoElement {

xilem_core/src/lib.rs

@@ -24,7 +24,6 @@
 #![warn(clippy::print_stdout, clippy::print_stderr)]
 // TODO: Remove any items listed as "Deferred"
 #![deny(clippy::trivially_copy_pass_by_ref)]
-#![expect(missing_debug_implementations, reason = "Deferred: Noisy")]
 #![expect(unused_qualifications, reason = "Deferred: Noisy")]
 #![expect(single_use_lifetimes, reason = "Deferred: Noisy")]
 #![expect(clippy::exhaustive_enums, reason = "Deferred: Noisy")]

xilem_core/src/message.rs

@@ -11,7 +11,7 @@ use core::ops::Deref;
 /// The possible outcomes from a [`View::message`]
 ///
 /// [`View::message`]: crate::View::message
-#[derive(Default)]
+#[derive(Default, Debug)]
 pub enum MessageResult<Action, Message = DynMessage> {
     /// An action for a parent message handler to use
     ///

xilem_core/src/sequence.rs

@@ -197,6 +197,7 @@ where
 
 /// The state used to implement `ViewSequence` for `Option<impl ViewSequence>`
 #[allow(unnameable_types)] // reason: Implementation detail, public because of trait visibility rules
+#[derive(Debug)]
 pub struct OptionSeqState<InnerState> {
     /// The current state.
     ///
@@ -341,6 +342,7 @@ where
 // This is managed in [`create_generational_view_id`] and [`view_id_to_index_generation`]
 #[doc(hidden)]
 #[allow(unnameable_types)] // reason: Implementation detail, public because of trait visibility rules
+#[derive(Debug)]
 pub struct VecViewState<InnerState> {
     inner_states: Vec<InnerState>,
 

xilem_core/src/view.rs

@@ -206,6 +206,7 @@ where
 }
 
 #[allow(unnameable_types)] // reason: Implementation detail, public because of trait visibility rules
+#[derive(Debug)]
 pub struct RcState<ViewState> {
     view_state: ViewState,
     /// This is a flag that is set, when an inner view signifies that it requires a rebuild (via [`MessageResult::RequestRebuild`]).

xilem_core/src/views/adapt.rs

@@ -6,6 +6,7 @@ use core::marker::PhantomData;
 use crate::{MessageResult, Mut, View, ViewId, ViewMarker, ViewPathTracker};
 
 /// A view that wraps a child view and modifies the state that callbacks have access to.
+#[derive(Debug)]
 pub struct Adapt<
     ParentState,
     ParentAction,
@@ -37,6 +38,7 @@ pub struct Adapt<
 ///
 /// The closure passed to [`Adapt`] should call this thunk with the child's
 /// app state.
+#[derive(Debug)]
 pub struct AdaptThunk<'a, ChildState, ChildAction, Context, ChildView, Message>
 where
     Context: ViewPathTracker,