ESDL

Event-sourcing Schema Definition Language

Schema definition language for defining aggregates, commands, events & custom types.

Heavily inspired by GraphQL syntax, you can describe aggregates which can be used for codegen in different languages.

Install

Due to the wit-bindgen project not having their crates published yet (see https://github.com/bytecodealliance/wit-bindgen/issues/180), esdl is not up to date on crates.io and it's advised to use the git url as the dependency for now.

toml esdl = { git = "https://github.com/thalo-rs/esdl", features = ["codegen-rust"] }

Possible features include codegen-rust, codegen-rust-wasm and codegen-typescript.

Code generation

ESDL schemas can be used for code generation.

The Rust crate currently supports code generation for:

• Rust (codegen-rust)
• Rust WASM (codegen-rust-wasm)
• TypeScript (codegen-typescript)

Additional languages may be added in the future. Contributions are welcome!

Example

``` version = "0.1.0"

aggregate BankAccount { openaccount(initialbalance: Float) -> OpenedAccount depositfunds(amount: Float) -> ReceivedFunds withdrawfunds(amount: Float) -> SentFunds send_funds(amount: Float, user: User) -> (SentFunds? | ReceivedFunds?) }

event OpenedAccount { initial_balance: Float }

event SentFunds { amount: Float user: User? }

event ReceivedFunds { amount: Float user: User? }

type User { id: String name: String? } ```

Scalar Types

| Scalar | Rust Type | TypeScript Type | | -------- | ----------- | --------------- | | String | [String] | string | | Int | [i32] | number | | Long | [i64] | number | | Float | [f32] | number | | Double | [f64] | number | | Bool | [bool] | boolean | | Bytes | [Vec<u8>] | string |

Optional & Required

Types can be marked as optional by adding the ? suffix.

| Type | Syntax | Example | | -------- | ------ | --------- | | Required | T | String | | Optional | T? | String? |

Repeating Types

Types can be repeated by wrapping them in [].

| Type | Syntax | Example | | ------ | ------ | ---------- | | Single | T | String | | Array | [T] | [String] |

Remember, we can mark types as optional, even in arrays.

| Type | Syntax | Example | | -------------------- | ------- | ------------ | | Optional Array | [T?]? | [String?]? | | Required Array | [T?] | [String?] | | Required Array Items | [T]? | [String]? | | Required Array Items | [T] | [String] |

Integrates with Thalo to generate Rust code.