1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373
//! [![github]](https://github.com/dtolnay/typetag) [![crates-io]](https://crates.io/crates/typetag) [![docs-rs]](https://docs.rs/typetag)
//!
//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,PHN2ZyByb2xlPSJpbWciIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgdmlld0JveD0iMCAwIDUxMiA1MTIiPjxwYXRoIGZpbGw9IiNmNWY1ZjUiIGQ9Ik00ODguNiAyNTAuMkwzOTIgMjE0VjEwNS41YzAtMTUtOS4zLTI4LjQtMjMuNC0zMy43bC0xMDAtMzcuNWMtOC4xLTMuMS0xNy4xLTMuMS0yNS4zIDBsLTEwMCAzNy41Yy0xNC4xIDUuMy0yMy40IDE4LjctMjMuNCAzMy43VjIxNGwtOTYuNiAzNi4yQzkuMyAyNTUuNSAwIDI2OC45IDAgMjgzLjlWMzk0YzAgMTMuNiA3LjcgMjYuMSAxOS45IDMyLjJsMTAwIDUwYzEwLjEgNS4xIDIyLjEgNS4xIDMyLjIgMGwxMDMuOS01MiAxMDMuOSA1MmMxMC4xIDUuMSAyMi4xIDUuMSAzMi4yIDBsMTAwLTUwYzEyLjItNi4xIDE5LjktMTguNiAxOS45LTMyLjJWMjgzLjljMC0xNS05LjMtMjguNC0yMy40LTMzLjd6TTM1OCAyMTQuOGwtODUgMzEuOXYtNjguMmw4NS0zN3Y3My4zek0xNTQgMTA0LjFsMTAyLTM4LjIgMTAyIDM4LjJ2LjZsLTEwMiA0MS40LTEwMi00MS40di0uNnptODQgMjkxLjFsLTg1IDQyLjV2LTc5LjFsODUtMzguOHY3NS40em0wLTExMmwtMTAyIDQxLjQtMTAyLTQxLjR2LS42bDEwMi0zOC4yIDEwMiAzOC4ydi42em0yNDAgMTEybC04NSA0Mi41di03OS4xbDg1LTM4Ljh2NzUuNHptMC0xMTJsLTEwMiA0MS40LTEwMi00MS40di0uNmwxMDItMzguMiAxMDIgMzguMnYuNnoiPjwvcGF0aD48L3N2Zz4K
//!
//! <br>
//!
//! **Serde serializable and deserializable trait objects.**
//!
//! This crate provides a macro for painless serialization of `&dyn Trait` trait
//! objects and serialization + deserialization of `Box<dyn Trait>` trait
//! objects.
//!
//! Let's dive into the example and I'll explain some more below.
//!
//! <br>
//!
//! # Example
//!
//! Suppose I have a trait `WebEvent` and I require that every implementation of
//! the trait be serializable and deserializable so that I can send them to my
//! ad-serving AI. Here are just the types and trait impls to start with:
//!
//! ```
//! # use serde::{Serialize, Deserialize};
//! #
//! trait WebEvent {
//! fn inspect(&self);
//! }
//!
//! #[derive(Serialize, Deserialize)]
//! struct PageLoad;
//!
//! impl WebEvent for PageLoad {
//! fn inspect(&self) {
//! println!("200 milliseconds or bust");
//! }
//! }
//!
//! #[derive(Serialize, Deserialize)]
//! struct Click {
//! x: i32,
//! y: i32,
//! }
//!
//! impl WebEvent for Click {
//! fn inspect(&self) {
//! println!("negative space between the ads: x={} y={}", self.x, self.y);
//! }
//! }
//! ```
//!
//! We'll need to be able to send an arbitrary web event as JSON to the AI:
//!
//! ```
//! # use serde::{Serialize, Serializer};
//! # use serde_json::Result;
//! #
//! # trait WebEvent {}
//! #
//! # impl<'a> Serialize for dyn WebEvent + 'a {
//! # fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
//! # where
//! # S: Serializer,
//! # {
//! # unimplemented!()
//! # }
//! # }
//! #
//! # fn somehow_send_json(json: String) -> Result<()> {
//! # unimplemented!()
//! # }
//! #
//! fn send_event_to_money_factory(event: &dyn WebEvent) -> Result<()> {
//! let json = serde_json::to_string(event)?;
//! somehow_send_json(json)?;
//! Ok(())
//! }
//! ```
//!
//! and receive an arbitrary web event as JSON on the server side:
//!
//! ```
//! # use serde::{Deserialize, Deserializer};
//! # use serde_json::Result;
//! #
//! # trait WebEvent {}
//! #
//! # impl<'de> Deserialize<'de> for Box<dyn WebEvent> {
//! # fn deserialize<D>(deserializer: D) -> std::result::Result<Self, D::Error>
//! # where
//! # D: Deserializer<'de>,
//! # {
//! # unimplemented!()
//! # }
//! # }
//! #
//! # fn overanalyze(event: Box<dyn WebEvent>) -> Result<()> {
//! # unimplemented!()
//! # }
//! #
//! fn process_event_from_clickfarm(json: &str) -> Result<()> {
//! let event: Box<dyn WebEvent> = serde_json::from_str(json)?;
//! overanalyze(event)?;
//! Ok(())
//! }
//! ```
//!
//! The introduction claimed that this would be painless but I'll let you be the
//! judge.
//!
//! First stick an attribute on top of the trait.
//!
//! ```
//! #[typetag::serde(tag = "type")]
//! trait WebEvent {
//! fn inspect(&self);
//! }
//! ```
//!
//! Then stick a similar attribute on all those impl blocks too.
//!
//! ```
//! # use serde::{Serialize, Deserialize};
//! #
//! # #[typetag::serde(tag = "type")]
//! # trait WebEvent {
//! # fn inspect(&self);
//! # }
//! #
//! # #[derive(Serialize, Deserialize)]
//! # struct PageLoad;
//! #
//! # #[derive(Serialize, Deserialize)]
//! # struct Click {
//! # x: i32,
//! # y: i32,
//! # }
//! #
//! #[typetag::serde]
//! impl WebEvent for PageLoad {
//! fn inspect(&self) {
//! println!("200 milliseconds or bust");
//! }
//! }
//!
//! #[typetag::serde]
//! impl WebEvent for Click {
//! fn inspect(&self) {
//! println!("negative space between the ads: x={} y={}", self.x, self.y);
//! }
//! }
//! ```
//!
//! And now it works as described. All in all, three lines were added!
//!
//! <br>
//!
//! # What?
//!
//! Trait objects are serialized by this library like Serde enums. Every impl of
//! the trait (anywhere in the program) looks like one variant of the enum.
//!
//! All three of Serde's tagged [enum representations] are supported. The one
//! shown above is the "internally tagged" style so our two event types would be
//! represented in JSON as:
//!
//! [enum representations]: https://serde.rs/enum-representations.html
//!
//! ```json
//! {"type":"PageLoad"}
//! {"type":"Click","x":10,"y":10}
//! ```
//!
//! The choice of enum representation is controlled by the attribute that goes
//! on the trait definition. Let's check out the "adjacently tagged" style:
//!
//! ```
//! #[typetag::serde(tag = "type", content = "value")]
//! trait WebEvent {
//! fn inspect(&self);
//! }
//! ```
//!
//! ```json
//! {"type":"PageLoad","value":null}
//! {"type":"Click","value":{"x":10,"y":10}}
//! ```
//!
//! and the "externally tagged" style, which is Serde's default for enums:
//!
//! ```
//! #[typetag::serde]
//! trait WebEvent {
//! fn inspect(&self);
//! }
//! ```
//!
//! ```json
//! {"PageLoad":null}
//! {"Click":{"x":10,"y":10}}
//! ```
//!
//! Separately, the value of the tag for a given trait impl may be defined as
//! part of the attribute that goes on the trait impl. By default the tag will
//! be the type name when no name is specified explicitly.
//!
//! ```
//! # use serde::{Serialize, Deserialize};
//! #
//! # #[typetag::serde]
//! # trait WebEvent {
//! # fn inspect(&self);
//! # }
//! #
//! # #[derive(Serialize, Deserialize)]
//! # struct Click {
//! # x: i32,
//! # y: i32,
//! # }
//! #
//! #[typetag::serde(name = "mouse_button_down")]
//! impl WebEvent for Click {
//! fn inspect(&self) {
//! println!("negative space between the ads: ({}, {})", self.x, self.y);
//! }
//! }
//! ```
//!
//! ```json
//! {"type":"mouse_button_down","x":10,"y":10}
//! ```
//!
//! Conceptually all you're getting with this crate is that we build for you an
//! enum in which every impl of the trait in your program is automatically
//! registered as an enum variant. The behavior is the same as if you had
//! written the enum yourself and implemented Serialize and Deserialize for the
//! dyn Trait object in terms of the enum.
//!
//! ```
//! # use serde::{Serialize, Deserialize};
//! #
//! # #[derive(Serialize, Deserialize)]
//! # struct PageLoad;
//! #
//! # #[derive(Serialize, Deserialize)]
//! # struct Click;
//! #
//! // generated (conceptually)
//! #[derive(Serialize, Deserialize)]
//! enum WebEvent {
//! PageLoad(PageLoad),
//! Click(Click),
//! /* ... */
//! }
//! ```
//!
//! <br>
//!
//! # So many questions
//!
//! - *Does it work if the trait impls are spread across different crates?*
//! **Yes**
//!
//! Serialization and deserialization both support every single impl of the
//! trait across the dependency graph of the final program binary.
//!
//! - *Does it work in non-self-describing data formats like Bincode?* **Yes**
//!
//! All three choices of enum representation will round-trip correctly through
//! compact binary formats including Bincode.
//!
//! - *Does it support non-struct types?* **Yes**
//!
//! The implementations of the trait can be structs, enums, primitives, or
//! anything else supported by Serde. The Serialize and Deserialize impls may
//! be derived or handwritten.
//!
//! - *Didn't someone explain to me why this wasn't possible?* **Yes**
//!
//! It might have been me.
//!
//! - *Then how does it work?*
//!
//! We use the [`inventory`] crate to produce a registry of impls of your
//! trait, which is built on the [`ctor`] crate to hook up initialization
//! functions that insert into the registry. The first `Box<dyn Trait>`
//! deserialization will perform the work of iterating the registry and
//! building a map of tags to deserialization functions. Subsequent
//! deserializations find the right deserialization function in that map. The
//! [`erased-serde`] crate is also involved, to do this all in a way that does
//! not break object safety.
//!
//! [`inventory`]: https://github.com/dtolnay/inventory
//! [`ctor`]: https://github.com/mmastrac/rust-ctor
//! [`erased-serde`]: https://github.com/dtolnay/erased-serde
#![allow(
clippy::missing_errors_doc,
clippy::module_name_repetitions,
clippy::unnested_or_patterns
)]
#[doc(hidden)]
pub use typetag_impl::*;
// Not public API. Used by generated code.
#[doc(hidden)]
pub use inventory;
// Not public API. Used by generated code.
#[doc(hidden)]
pub use erased_serde;
// Not public API. Used by generated code.
#[doc(hidden)]
pub use serde;
// Not public API. Used by generated code.
#[doc(hidden)]
pub use once_cell;
// Not public API. Used by generated code.
#[doc(hidden)]
pub mod externally;
// Not public API. Used by generated code.
#[doc(hidden)]
pub mod internally;
// Not public API. Used by generated code.
#[doc(hidden)]
pub mod adjacently;
mod content;
mod de;
mod ser;
// Not public API. Used by generated code.
#[doc(hidden)]
pub type DeserializeFn<T> = fn(&mut dyn erased_serde::Deserializer) -> erased_serde::Result<Box<T>>;
use std::collections::BTreeMap;
// Not public API. Used by generated code.
#[doc(hidden)]
pub struct Registry<T: ?Sized> {
pub map: BTreeMap<&'static str, Option<DeserializeFn<T>>>,
pub names: Vec<&'static str>,
}
// Object-safe trait bound inserted by typetag serialization. We want this just
// so the serialization requirement appears on rustdoc's view of your trait.
// Otherwise not public API.
#[doc(hidden)]
pub trait Serialize: erased_serde::Serialize {}
impl<T: ?Sized> Serialize for T where T: erased_serde::Serialize {}
// Object-safe trait bound inserted by typetag deserialization. We want this
// just so the serialization requirement appears on rustdoc's view of your
// trait. Otherwise not public API.
#[doc(hidden)]
pub trait Deserialize {}
impl<T> Deserialize for T {}
// Not public API.
#[doc(hidden)]
pub trait Strictest {
type Object: ?Sized;
}