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Initial implementation of the Bevy Remote Protocol (Adopted) (#14880) 
# Objective

Adopted from #13563.

The goal is to implement the Bevy Remote Protocol over HTTP/JSON,
allowing the ECS to be interacted with remotely.

## Solution

At a high level, there are really two separate things that have been
undertaken here:
1. First, `RemotePlugin` has been created, which has the effect of
embedding a [JSON-RPC](https://www.jsonrpc.org/specification) endpoint
into a Bevy application.
2. Second, the [Bevy Remote Protocol
verbs](https://gist.github.com/coreh/1baf6f255d7e86e4be29874d00137d1d#file-bevy-remote-protocol-md)
(excluding `POLL`) have been implemented as remote methods for that
JSON-RPC endpoint under a Bevy-exclusive namespace (e.g. `bevy/get`,
`bevy/list`, etc.).

To avoid some repetition, here is the crate-level documentation, which
explains the request/response structure, built-in-methods, and custom
method configuration:
<details>
  <summary>Click to view crate-level docs</summary>

```rust
//! An implementation of the Bevy Remote Protocol over HTTP and JSON, to allow
//! for remote control of a Bevy app.
//!
//! Adding the [`RemotePlugin`] to your [`App`] causes Bevy to accept
//! connections over HTTP (by default, on port 15702) while your app is running.
//! These *remote clients* can inspect and alter the state of the
//! entity-component system. Clients are expected to `POST` JSON requests to the
//! root URL; see the `client` example for a trivial example of use.
//!
//! The Bevy Remote Protocol is based on the JSON-RPC 2.0 protocol.
//!
//! ## Request objects
//!
//! A typical client request might look like this:
//!
//! ```json
//! {
//!     "method": "bevy/get",
//!     "id": 0,
//!     "params": {
//!         "entity": 4294967298,
//!         "components": [
//!             "bevy_transform::components::transform::Transform"
//!         ]
//!     }
//! }
//! ```
//!
//! The `id` and `method` fields are required. The `param` field may be omitted
//! for certain methods:
//!
//! * `id` is arbitrary JSON data. The server completely ignores its contents,
//!   and the client may use it for any purpose. It will be copied via
//!   serialization and deserialization (so object property order, etc. can't be
//!   relied upon to be identical) and sent back to the client as part of the
//!   response.
//!
//! * `method` is a string that specifies one of the possible [`BrpRequest`]
//!   variants: `bevy/query`, `bevy/get`, `bevy/insert`, etc. It's case-sensitive.
//!
//! * `params` is parameter data specific to the request.
//!
//! For more information, see the documentation for [`BrpRequest`].
//! [`BrpRequest`] is serialized to JSON via `serde`, so [the `serde`
//! documentation] may be useful to clarify the correspondence between the Rust
//! structure and the JSON format.
//!
//! ## Response objects
//!
//! A response from the server to the client might look like this:
//!
//! ```json
//! {
//!     "jsonrpc": "2.0",
//!     "id": 0,
//!     "result": {
//!         "bevy_transform::components::transform::Transform": {
//!             "rotation": { "x": 0.0, "y": 0.0, "z": 0.0, "w": 1.0 },
//!             "scale": { "x": 1.0, "y": 1.0, "z": 1.0 },
//!             "translation": { "x": 0.0, "y": 0.5, "z": 0.0 }
//!         }
//!     }
//! }
//! ```
//!
//! The `id` field will always be present. The `result` field will be present if the
//! request was successful. Otherwise, an `error` field will replace it.
//!
//! * `id` is the arbitrary JSON data that was sent as part of the request. It
//!   will be identical to the `id` data sent during the request, modulo
//!   serialization and deserialization. If there's an error reading the `id` field,
//!   it will be `null`.
//!
//! * `result` will be present if the request succeeded and will contain the response
//!   specific to the request.
//!
//! * `error` will be present if the request failed and will contain an error object
//!   with more information about the cause of failure.
//!
//! ## Error objects
//!
//! An error object might look like this:
//!
//! ```json
//! {
//!     "code": -32602,
//!     "message": "Missing \"entity\" field"
//! }
//! ```
//!
//! The `code` and `message` fields will always be present. There may also be a `data` field.
//!
//! * `code` is an integer representing the kind of an error that happened. Error codes documented
//!   in the [`error_codes`] module.
//!
//! * `message` is a short, one-sentence human-readable description of the error.
//!
//! * `data` is an optional field of arbitrary type containing additional information about the error.
//!
//! ## Built-in methods
//!
//! The Bevy Remote Protocol includes a number of built-in methods for accessing and modifying data
//! in the ECS. Each of these methods uses the `bevy/` prefix, which is a namespace reserved for
//! BRP built-in methods.
//!
//! ### bevy/get
//!
//! Retrieve the values of one or more components from an entity.
//!
//! `params`:
//! - `entity`: The ID of the entity whose components will be fetched.
//! - `components`: An array of fully-qualified type names of components to fetch.
//!
//! `result`: A map associating each type name to its value on the requested entity.
//!
//! ### bevy/query
//!
//! Perform a query over components in the ECS, returning all matching entities and their associated
//! component values.
//!
//! All of the arrays that comprise this request are optional, and when they are not provided, they
//! will be treated as if they were empty.
//!
//! `params`:
//! `params`:
//! - `data`:
//!   - `components` (optional): An array of fully-qualified type names of components to fetch.
//!   - `option` (optional): An array of fully-qualified type names of components to fetch optionally.
//!   - `has` (optional): An array of fully-qualified type names of components whose presence will be
//!      reported as boolean values.
//! - `filter` (optional):
//!   - `with` (optional): An array of fully-qualified type names of components that must be present
//!     on entities in order for them to be included in results.
//!   - `without` (optional): An array of fully-qualified type names of components that must *not* be
//!     present on entities in order for them to be included in results.
//!
//! `result`: An array, each of which is an object containing:
//! - `entity`: The ID of a query-matching entity.
//! - `components`: A map associating each type name from `components`/`option` to its value on the matching
//!   entity if the component is present.
//! - `has`: A map associating each type name from `has` to a boolean value indicating whether or not the
//!   entity has that component. If `has` was empty or omitted, this key will be omitted in the response.
//!
//! ### bevy/spawn
//!
//! Create a new entity with the provided components and return the resulting entity ID.
//!
//! `params`:
//! - `components`: A map associating each component's fully-qualified type name with its value.
//!
//! `result`:
//! - `entity`: The ID of the newly spawned entity.
//!
//! ### bevy/destroy
//!
//! Despawn the entity with the given ID.
//!
//! `params`:
//! - `entity`: The ID of the entity to be despawned.
//!
//! `result`: null.
//!
//! ### bevy/remove
//!
//! Delete one or more components from an entity.
//!
//! `params`:
//! - `entity`: The ID of the entity whose components should be removed.
//! - `components`: An array of fully-qualified type names of components to be removed.
//!
//! `result`: null.
//!
//! ### bevy/insert
//!
//! Insert one or more components into an entity.
//!
//! `params`:
//! - `entity`: The ID of the entity to insert components into.
//! - `components`: A map associating each component's fully-qualified type name with its value.
//!
//! `result`: null.
//!
//! ### bevy/reparent
//!
//! Assign a new parent to one or more entities.
//!
//! `params`:
//! - `entities`: An array of entity IDs of entities that will be made children of the `parent`.
//! - `parent` (optional): The entity ID of the parent to which the child entities will be assigned.
//!   If excluded, the given entities will be removed from their parents.
//!
//! `result`: null.
//!
//! ### bevy/list
//!
//! List all registered components or all components present on an entity.
//!
//! When `params` is not provided, this lists all registered components. If `params` is provided,
//! this lists only those components present on the provided entity.
//!
//! `params` (optional):
//! - `entity`: The ID of the entity whose components will be listed.
//!
//! `result`: An array of fully-qualified type names of components.
//!
//! ## Custom methods
//!
//! In addition to the provided methods, the Bevy Remote Protocol can be extended to include custom
//! methods. This is primarily done during the initialization of [`RemotePlugin`], although the
//! methods may also be extended at runtime using the [`RemoteMethods`] resource.
//!
//! ### Example
//! ```ignore
//! fn main() {
//!     App::new()
//!         .add_plugins(DefaultPlugins)
//!         .add_plugins(
//!             // `default` adds all of the built-in methods, while `with_method` extends them
//!             RemotePlugin::default()
//!                 .with_method("super_user/cool_method".to_owned(), path::to::my:🆒:handler)
//!                 // ... more methods can be added by chaining `with_method`
//!         )
//!         .add_systems(
//!             // ... standard application setup
//!         )
//!         .run();
//! }
//! ```
//!
//! The handler is expected to be a system-convertible function which takes optional JSON parameters
//! as input and returns a [`BrpResult`]. This means that it should have a type signature which looks
//! something like this:
//! ```
//! # use serde_json::Value;
//! # use bevy_ecs::prelude::{In, World};
//! # use bevy_remote::BrpResult;
//! fn handler(In(params): In<Option<Value>>, world: &mut World) -> BrpResult {
//!     todo!()
//! }
//! ```
//!
//! Arbitrary system parameters can be used in conjunction with the optional `Value` input. The
//! handler system will always run with exclusive `World` access.
//!
//! [the `serde` documentation]: https://serde.rs/
```

</details>

### Message lifecycle

At a high level, the lifecycle of client-server interactions is
something like this:
1. The client sends one or more `BrpRequest`s. The deserialized version
of that is just the Rust representation of a JSON-RPC request, and it
looks like this:
```rust
pub struct BrpRequest {
    /// The action to be performed. Parsing is deferred for the sake of error reporting.
    pub method: Option<Value>,

    /// Arbitrary data that will be returned verbatim to the client as part of
    /// the response.
    pub id: Option<Value>,

    /// The parameters, specific to each method.
    ///
    /// These are passed as the first argument to the method handler.
    /// Sometimes params can be omitted.
    pub params: Option<Value>,
}
```
2. These requests are accumulated in a mailbox resource (small lie but
close enough).
3. Each update, the mailbox is drained by a system
`process_remote_requests`, where each request is processed according to
its `method`, which has an associated handler. Each handler is a Bevy
system that runs with exclusive world access and returns a result; e.g.:
```rust
pub fn process_remote_get_request(In(params): In<Option<Value>>, world: &World) -> BrpResult { // ... }
```
4. The result (or an error) is reported back to the client.

## Testing

This can be tested by using the `server` and `client` examples. The
`client` example is not particularly exhaustive at the moment (it only
creates barebones `bevy/query` requests) but is still informative. Other
queries can be made using `curl` with the `server` example running.

For example, to make a `bevy/list` request and list all registered
components:
```bash
curl -X POST -d '{ "jsonrpc": "2.0", "id": 1, "method": "bevy/list" }' 127.0.0.1:15702 | jq .
```

---

## Future direction

There were a couple comments on BRP versioning while this was in draft.
I agree that BRP versioning is a good idea, but I think that it requires
some consensus on a couple fronts:
- First of all, what does the version actually mean? Is it a version for
the protocol itself or for the `bevy/*` methods implemented using it?
Both?
- Where does the version actually live? The most natural place is just
where we have `"jsonrpc"` right now (at least if it's versioning the
protocol itself), but this means we're not actually conforming to
JSON-RPC any more (so, for example, any client library used to construct
JSON-RPC requests would stop working). I'm not really against that, but
it's at least a real decision.
- What do we actually do when we encounter mismatched versions? Adding
handling for this would be actual scope creep instead of just a little
add-on in my opinion.

Another thing that would be nice is making the internal structure of the
implementation less JSON-specific. Right now, for example, component
values that will appear in server responses are quite eagerly converted
to JSON `Value`s, which prevents disentangling the handler logic from
the communication medium, but it can probably be done in principle and I
imagine it would enable more code reuse (e.g. for custom method
handlers) in addition to making the internals more readily usable for
other formats.

---------

Co-authored-by: Patrick Walton <pcwalton@mimiga.net>
Co-authored-by: DragonGamesStudios <margos.michal@gmail.com>
Co-authored-by: Christopher Biscardi <chris@christopherbiscardi.com>
Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>
2024-09-23 18:36:16 +00:00
.cargo Use lld for rustdoc on Linux in config_fast_builds.toml (#14839) 2024-08-22 23:08:04 +00:00
.github Bump crate-ci/typos from 1.24.5 to 1.24.6 (#15383) 2024-09-23 17:38:38 +00:00
assets Implement percentage-closer soft shadows (PCSS). (#13497) 2024-09-18 18:07:17 +00:00
benches Bubbling observers traversal should use query data (#15385) 2024-09-23 18:08:36 +00:00
crates Initial implementation of the Bevy Remote Protocol (Adopted) (#14880) 2024-09-23 18:36:16 +00:00
docs Initial implementation of the Bevy Remote Protocol (Adopted) (#14880) 2024-09-23 18:36:16 +00:00
docs-template Fix common capitalization errors in documentation (#14562) 2024-07-31 21:16:05 +00:00
errors Generate links to definition in source code pages on docs.rs and dev-docs.bevyengine.org (#12965) 2024-07-29 23:10:16 +00:00
examples Initial implementation of the Bevy Remote Protocol (Adopted) (#14880) 2024-09-23 18:36:16 +00:00
src Fix common capitalization errors in documentation (#14562) 2024-07-31 21:16:05 +00:00
tests Broaden "Check for bevy_internal imports" CI Task (#15333) 2024-09-20 17:08:37 +00:00
tools remove cfg-check in ci tool (#15063) 2024-09-08 17:12:35 +00:00
.gitattributes Enforce linux-style line endings for .rs and .toml (#3197) 2021-11-26 21:05:35 +00:00
.gitignore Remove redundent information and optimize dynamic allocations in Table (#12929) 2024-09-16 22:52:05 +00:00
Cargo.toml Initial implementation of the Bevy Remote Protocol (Adopted) (#14880) 2024-09-23 18:36:16 +00:00
clippy.toml Enable clippy::check-private-items so that missing_safety_doc will apply to private functions as well (#15161) 2024-09-18 15:28:41 +00:00
CODE_OF_CONDUCT.md Update CODE_OF_CONDUCT.md 2020-08-19 20:25:58 +01:00
CONTRIBUTING.md Deprecate old contributing documentation / information (#14885) 2024-08-23 11:47:02 +00:00
CREDITS.md Programmed soundtrack example (#12774) 2024-03-29 20:32:30 +00:00
deny.toml Fix duplicate dependencies on raw-window-handle (#12309) 2024-03-05 08:24:37 +00:00
LICENSE-APACHE Let the project page support GitHub's new ability to display open source licenses (#4966) 2022-06-08 17:55:57 +00:00
LICENSE-MIT Let the project page support GitHub's new ability to display open source licenses (#4966) 2022-06-08 17:55:57 +00:00
README.md Update funding link (#12425) 2024-03-11 21:46:04 +00:00
rustfmt.toml Cargo fmt with unstable features (#1903) 2021-04-21 23:19:34 +00:00
typos.toml Implement percentage-closer soft shadows (PCSS). (#13497) 2024-09-18 18:07:17 +00:00

README.md

Bevy

License Crates.io Downloads Docs CI Discord

What is Bevy?

Bevy is a refreshingly simple data-driven game engine built in Rust. It is free and open-source forever!

WARNING

Bevy is still in the early stages of development. Important features are missing. Documentation is sparse. A new version of Bevy containing breaking changes to the API is released approximately once every 3 months. We provide migration guides, but we can't guarantee migrations will always be easy. Use only if you are willing to work in this environment.

MSRV: Bevy relies heavily on improvements in the Rust language and compiler. As a result, the Minimum Supported Rust Version (MSRV) is generally close to "the latest stable release" of Rust.

Design Goals

  • Capable: Offer a complete 2D and 3D feature set
  • Simple: Easy for newbies to pick up, but infinitely flexible for power users
  • Data Focused: Data-oriented architecture using the Entity Component System paradigm
  • Modular: Use only what you need. Replace what you don't like
  • Fast: App logic should run quickly, and when possible, in parallel
  • Productive: Changes should compile quickly ... waiting isn't fun

About

  • Features: A quick overview of Bevy's features.
  • News: A development blog that covers our progress, plans and shiny new features.

Docs

Community

Before contributing or participating in discussions with the community, you should familiarize yourself with our Code of Conduct.

  • Discord: Bevy's official discord server.
  • Reddit: Bevy's official subreddit.
  • GitHub Discussions: The best place for questions about Bevy, answered right here!
  • Bevy Assets: A collection of awesome Bevy projects, tools, plugins and learning materials.

Contributing

If you'd like to help build Bevy, check out the Contributor's Guide. For simple problems, feel free to open an issue or PR and tackle it yourself!

For more complex architecture decisions and experimental mad science, please open an RFC (Request For Comments) so we can brainstorm together effectively!

Getting Started

We recommend checking out the Quick Start Guide for a brief introduction.

Follow the Setup guide to ensure your development environment is set up correctly. Once set up, you can quickly try out the examples by cloning this repo and running the following commands:

# Switch to the correct version (latest release, default is main development branch)
git checkout latest
# Runs the "breakout" example
cargo run --example breakout

To draw a window with standard functionality enabled, use:

use bevy::prelude::*;

fn main(){
  App::new()
    .add_plugins(DefaultPlugins)
    .run();
}

Fast Compiles

Bevy can be built just fine using default configuration on stable Rust. However for really fast iterative compiles, you should enable the "fast compiles" setup by following the instructions here.

Bevy Cargo Features

This list outlines the different cargo features supported by Bevy. These allow you to customize the Bevy feature set for your use-case.

Thanks

Bevy is the result of the hard work of many people. A huge thanks to all Bevy contributors, the many open source projects that have come before us, the Rust gamedev ecosystem, and the many libraries we build on.

A huge thanks to Bevy's generous sponsors. Bevy will always be free and open source, but it isn't free to make. Please consider sponsoring our work if you like what we're building.

This project is tested with BrowserStack.

License

Bevy is free, open source and permissively licensed! Except where noted (below and/or in individual files), all code in this repository is dual-licensed under either:

at your option. This means you can select the license you prefer! This dual-licensing approach is the de-facto standard in the Rust ecosystem and there are very good reasons to include both.

Some of the engine's code carries additional copyright notices and license terms due to their external origins. These are generally BSD-like, but exact details vary by crate: If the README of a crate contains a 'License' header (or similar), the additional copyright notices and license terms applicable to that crate will be listed. The above licensing requirement still applies to contributions to those crates, and sections of those crates will carry those license terms. The license field of each crate will also reflect this. For example, bevy_mikktspace has code under the Zlib license (as well as a copyright notice when choosing the MIT license).

The assets included in this repository (for our examples) typically fall under different open licenses. These will not be included in your game (unless copied in by you), and they are not distributed in the published bevy crates. See CREDITS.md for the details of the licenses of those files.

Your contributions

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.