Basic serialization example (#560)

Author: Vrixyz

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+# Unreleased
+
+## Added
+
+- Added a serialization `serialization2` example for `bevy_rapier2d`.
+
 ## v0.29.0 (18 February 2025)
 
 ### Added

bevy_rapier2d/Cargo.toml

@@ -84,6 +84,7 @@ glam = { version = "0.29", features = ["approx"] }
 bevy-inspector-egui = "0.28.0"
 bevy_egui = "0.31"
 bevy_mod_debugdump = "0.12"
+serde_json = "1.0"
 
 [package.metadata.docs.rs]
 # Enable all the features when building the docs on docs.rs

bevy_rapier2d/examples/joints2.rs

@@ -1,6 +1,7 @@
 use bevy::prelude::*;
 use bevy_rapier2d::prelude::*;
 
+#[allow(unused)]
 fn main() {
     App::new()
         .insert_resource(ClearColor(Color::srgb(

bevy_rapier2d/examples/serialization2.rs

@@ -0,0 +1,40 @@
+//! Example for RapierContext serialization, run with `--features serde-serialize`.
+
+use bevy::prelude::*;
+use bevy::MinimalPlugins;
+use bevy_rapier2d::prelude::*;
+
+/// Note: This will end up in duplication for testbed, but that's more simple.
+mod joints2;
+
+fn main() {
+    App::new()
+        .insert_resource(ClearColor(Color::srgb(
+            0xF9 as f32 / 255.0,
+            0xF9 as f32 / 255.0,
+            0xFF as f32 / 255.0,
+        )))
+        .add_plugins((
+            MinimalPlugins,
+            RapierPhysicsPlugin::<NoUserData>::pixels_per_meter(100.0),
+        ))
+        .add_systems(Startup, joints2::setup_physics)
+        .add_systems(PostUpdate, print_physics)
+        .add_systems(Last, quit)
+        .run();
+}
+
+pub fn print_physics(_context: ReadRapierContext) {
+    #[cfg(feature = "serde-serialize")]
+    println!(
+        "{}",
+        serde_json::to_string_pretty(&_context.single())
+            .expect("Unable to serialize `RapierContext`")
+    );
+    #[cfg(not(feature = "serde-serialize"))]
+    panic!("Example 'serialization' should be run with '--features serde-serialize'.");
+}
+
+fn quit(mut exit_event: EventWriter<AppExit>) {
+    exit_event.send(AppExit::Success);
+}

src/plugin/context/systemparams/rapier_context_systemparam.rs

@@ -57,6 +57,7 @@ impl<'w, 's, T: query::QueryFilter + 'static> ReadRapierContext<'w, 's, T> {
 /// This helps with reducing boilerplate, at the (small) price of maybe getting too much information from the ECS.
 ///
 /// Note: This is not a component, refer to [`ReadRapierContext`], [`WriteRapierContext`], or [`RapierContextSimulation`]
+#[cfg_attr(feature = "serde-serialize", derive(Serialize))]
 #[derive(query::QueryData)]
 pub struct RapierContext<'a> {
     /// The Rapier context, containing all the state of the physics engine.