# gleam_package_interface
[](https://hex.pm/packages/gleam_package_interface)
[](https://hexdocs.pm/gleam_package_interface/)
## Installation
Add `gleam_package_interface` to your Gleam project:
```sh
gleam add gleam_package_interface
```
## What's a package interface?
Whenever you build your project's documentation with `gleam docs build`, the
Gleam compiler will also produce a handy json file
`./build/dev/docs/<your package>/package-interface.json`
containing data about your package: that's the package interface.
It has all public information your package exposes to the outside world: type
definitions, type aliases, public functions and constants — each annotated with
its own type and with its documentation.
> You can also have the compiler build the package interface using the
> `gleam export package-interface` command.
Let's have a look at a small example. Imagine you have a module called `wibble`
with the following definition:
```gleam
/// Documentation!
pub fn wibbler(label n: Int) -> Int {
todo
}
```
The resulting package interface will look something like this (some keys where
omitted to keep the example short):
```json
{
"package": "your package",
"modules": {
"wibble": {
"functions": {
"wibbler": {
"documentation": "Documentation!\n",
"parameters": [
{
"label": "label",
"type": {
"kind": "named",
"package": "",
"module": "gleam",
"name": "Int"
}
}
],
"return": {
"kind": "named",
"package": "",
"module": "gleam",
"name": "Int"
}
}
}
}
}
}
```
To get a proper feel of the structure of the generated package interface you can
have a look at this
[package's types](https://hexdocs.pm/gleam_package_interface/).
## Usage
This package provides Gleam types to describe a package interface and a
`decoder` to decode the json package interface into a Gleam value.
```gleam
// gleam add gleam_json
// gleam add simplifile
import gleam/json
import gleam/package_interface
import simplifile
pub fn main() {
let assert Ok(json) = simplifile.read("path to the package interface")
let assert Ok(interface) = json.decode(json, using: package_interface.decoder)
todo as "now you can use the package interface however you want!"
}
```
