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.

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 {
  open_account(initial_balance: Float) -> OpenedAccount
  deposit_funds(amount: Float) -> ReceivedFunds
  withdraw_funds(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.