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libninja

libninja is a tool for generating world-class, idiomatic client libraries from OpenAPI specs.

The best way to see it in action is to see what it produces.

plaid-rs is generated entirely by Libninja. This includes:

  • The client library itself
  • Idiomatic interface, where required arguments are passed directly or as part of a struct, and optional arguments are included via method chaining.
  • Documentation is published online (docs.rs), and crate is published to registry (crates.io)
  • examples/ folder containing an example for every API endpoint
  • The API client has the ability to record/replay requests, greatly aiding development for end users.
  • API documentation is included in function docstrings, so it's available inline in the editor. The docstrings also include links to plaid's hosted API documentation.

All of that is created with this command:

libninja gen Plaid ~/path/to/plaid/openapi.yaml

Installation

cargo install --git https://github.com/kurtbuilds/libninja

Use the command line help to see required arguments & options when generating libraries.

Usage

Deriving traits for generated structs

You can derive traits for the generated structs by passing them using one (or many) --derive arguments:

libninja gen --derive oasgen::OaSchema --derive faker::Dummy Plaid ~/path/to/plaid/openapi.yaml

Make sure to add the referenced crate(s) (and any necessary features) to your Cargo.toml:

cargo add oasgen --features chrono

Then, the traits will be added to the derive attribute on the generated model and request structs:

use serde::{Serialize, Deserialize};
use super::Glossary;
#[derive(Debug, Clone, Serialize, Deserialize, Default, oasgen::OaSchema)]
pub struct ListGlossariesResponse {
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub glossaries: Option<Vec<Glossary>>,
}

Customizing Files

During codegen, libninja will examine the target directory for files or content it should keep (effectively, using the existing crate as a template). It looks for two directives, libninja: static and libninja: after.

If libninja encounters libninja: static, it will skip generation entirely, and keep the existing file as-is.

If libninja encounters libninja: after, it will overwrite any code encountered after that directive, replacing it with the generated code. Generally, use this when you want to customize the imports or add additional structs or functions to the file.

Importantly, libninja removes outdated code, so any handwritten file is not marked with libninja: static will be removed.

Customize the OpenAPI spec

Most OpenAPI specs you encounter in the real world are not perfect, and sometimes are entirely broken. You can manually modify the script or write a script to do so.

The preferred way is to write a script to modify the spec. You can use serde to deserialize the spec, modify it, and then serialize it back to disk. This way, you can rerun the same modifications every time the spec changes. This script can be a standalone crate (which can live in the same repo), or part of build.rs.

If the spec is invalid and doesn't deserialize, deserialize it as a serde_json::Value to make it compliant, and then deserialize again (serde_json::from_value) into a OpenAPI spec for further processing.

Alternatively, manually modifying the script is great for one-off changes, but your target spec might be evolving over time. You can use git diffings to partially address this, but it's not ideal. If you go this route, the openapi cli tool can help.

Roadmap

[ ] Decode anyOf into an enum (IB: submit order array item) [ ] Response structs can be newtype (IB: submit order) [ ] Put impl Client methods in the request module files. [ ] Make sure that request and response structs go in the request module files and not in model/