███████╗██╗░░░░░██╗░░░░░░█████╗░
██╔════╝██║░░░░░██║░░░░░██╔══██╗
█████╗░░██║░░░░░██║░░░░░███████║
██╔══╝░░██║░░░░░██║░░░░░██╔══██║
███████╗███████╗███████╗██║░░██║
╚══════╝╚══════╝╚══════╝╚═╝░░╚═╝ v0.2.0

Ella, is yet another compiler to produce Go and Typescript code based on simple and easy-to-read schema IDL. There are many tools like gRPC, Twirp or event WebRPC to generate codes, but this little compiler is designed based on my views of 12+ years of developing backends and APIs. I wanted to simplify the tooling and produce almost perfect optimized, handcrafted code that can be read and understood.

Ella's schema went through several iterations to make it easier for extension and backward compatibility in future releases.

NOTE:

Ella's code generated has been used in couple of production projects, it has some designs that might not fit your needs, but I think it might solve a large number of projects. Also Ella's only emit Go, as a server and client, and Typescript as only client. This is intentinal as it serves my needs. However it can be easily extetended to produce other languages code by traversing the generated AST. For getting some examples about that, please refer to generate-golang.go and generate-typescript.go

Installation

to install Ella's compiler, simply use the go install command

go install ella.to/[email protected]

Usage

Simplicity applies to the CLI command as well, it looks for all files that need to be compiled and outputs the result to the designated file. The extension of the output file tells the compiler whether you want to produce the typescript or golang code. That's pretty much of it.

For example, the following command, will generate api.gen.go in /api folder with the package name api and will read all the ella files inside ./schema folder.

ella gen api /api/api.gen.go ./schema/*.ella

Also, we can format the schema as well to have a consistent look by running the following command

ella fmt ./schema/*.ella

The full CLI documentation can be accessed by running Ella command without any arguments

███████╗██╗░░░░░██╗░░░░░░█████╗░
██╔════╝██║░░░░░██║░░░░░██╔══██╗
█████╗░░██║░░░░░██║░░░░░███████║
██╔══╝░░██║░░░░░██║░░░░░██╔══██║
███████╗███████╗███████╗██║░░██║
╚══════╝╚══════╝╚══════╝╚═╝░░╚═╝ v0.2.0

Usage: ella [command]

Commands:
  - fmt Format one or many files in place using glob pattern
        ella fmt <glob path>

  - gen Generate code from a folder to a file and currently
        supports .go and .ts extensions
        ella gen <pkg> <output path to file> <search glob paths...>

  - ver Print the version of ella

example:
  ella fmt ./path/to/*.ella
  ella gen rpc ./path/to/output.go ./path/to/*.ella
  ella gen rpc ./path/to/output.ts ./path/to/*.ella ./path/to/other/*.ella

Schema

Comment

comment can be created using #

for example

# this is a comment

Constant

const <identifier> = <identifier> | <value>

for example

const A = 1
const B = 1_000_000
const C = 1.23
const D = "hello world"
const E = 'hello world'
const F = `hello
world
`
const FileSize = 10gb
const Timeout = 2s

const RefFileSize = FileSize

Enum

enum <identifier> {
    <identifier> = <integer number>
    <identifier>
}

for example

enum UserRole {
    # _ skip the generation but keeps the order
    _ = 1
    Root
    Normal
}

Model

model <identifer> {
    # for extending the model
    ...<model's identifer>
    <identifier>: <type> {
        <identifier> = <value> | <const identifer>
    }
}

Service

service <Http | Rpc><identifer> {
    <identifier> (<identifer>: <type>) => (<identifer>: <type>) {
        <identifider> = <value> | <const identifer>
    }
}

# for example:

service HttpUserService {
    GetById(id: string) => (user: User)
    Create(name: string) => (user: User)
}

HTTP Service Methods

Ella supports 6 powerful communication patterns for HTTP services:

Method Type	Input	Output	Use Case
🔄 JSON-JSON	JSON	JSON	Standard API calls
📦 JSON-Binary	JSON	Binary	File downloads, media streaming
📡 JSON-SSE	JSON	Server-Sent Events	Real-time updates, notifications
📤 Files-JSON	File Upload	JSON	Upload processing with metadata return
📥 Files-Binary	File Upload	Binary	Process uploads and return binary data
📊 Files-SSE	File Upload	Server-Sent Events	Upload progress tracking, processing events

RPC Service Methods

RPC services focus on simplicity with a single communication pattern:

Method Type	Input	Output	Use Case
🔌 JSON-JSON	JSON	JSON	Internal service communication

For more examples of these method types, check the e2e folder

For more examples, please look into e2e folder

Identifier

there are 2 types of identifiers, camelCase and PascalCase. Basically all the args and returns names must be camelCase (first char must be lowercase) and all other identifer must be PascalCase (first char must be uppercase)

Custom Error

defining a custom error that can be safely used over the network. Code is optional. Code has to be unique. If Code is not defined, the compiler will assign a unique Id.

error <identifer> { Code = <Integer> Msg = "" }

Type

type can be either the following list or refer to Model's identifer

int8, int16, int32, int64
uint8, uint16, uint32, uint64
float32, float64
string
bool
timestamp
any
file
[]<type>
map<type, type>

Value

Literal values for constants and defaults: Numbers: 1, 1.2

• Strings: "hello", 'hello', hello
• Booleans: true, false
• Durations: 1ns, 1us, 1ms, 1s, 1m, 1h
• Sizes: 1b, 1kb, 1mb, 1gb, 1tb, 1pb, 1eb
• Null: null