petstore-api-custom-commands

name	petstore-api-custom-commands
description	How to author custom commands for the petstore-api CLI using the co-generated SDK.

Custom Commands for petstore-api

Overview

The petstore-api CLI supports user-authored custom commands that are compiled into the binary alongside the auto-generated API commands. Custom commands get a fully-wired SDK client that inherits the CLI's auth, retries, TLS, base URL, and global headers — zero configuration required.

Architecture

cli/petstore-api/custom.rs    ← Your command handlers (protected by .fernignore)
cli/petstore-api/sdk_glue.rs  ← Generated bridge: sdk_client() + block_on()
cli/petstore-api/main.rs      ← Generated entrypoint (calls custom::register)
petstore-api-sdk/             ← Co-generated typed SDK crate
petstore-api-types/           ← Co-generated typed model crate

Adding a Custom Command

1. Edit cli/petstore-api/custom.rs

This file is protected by .fernignore — fern generate will never overwrite it. Register commands in the register() function:

use petstore_api_sdk::api::*;

pub fn register(app: CliApp) -> CliApp {
    let app = app.command(
        clap::Command::new("get-pet")
            .about("Get a pet by ID")
            .arg(clap::Arg::new("petId").required(true))
        ,
        |matches, ctx| {
            let pet_id = matches.get_one::<String>("petId").unwrap();
            let client = super::sdk_glue::sdk_client(ctx);
            let result = super::sdk_glue::block_on(
                client.pets.get_pet(pet_id),
            )?;
            println!("{}", serde_json::to_string_pretty(&result).unwrap());
            Ok(())
        },
    );
    app
}

Then build and test:

cargo build
petstore-api get-pet <petId>

2. Available SDK Clients

The sdk_glue::sdk_client(ctx) call returns a petstore_api_sdk::api::Client with the following sub-clients:

Field	Type	Description
client.pets	petstore_api_sdk::api::PetsClient	pets operations
client.auth	petstore_api_sdk::api::AuthClient	auth operations

3. Key Patterns

Get the SDK client (execution-sharing, fully authenticated):

let client = super::sdk_glue::sdk_client(ctx);

Run an async SDK call from a sync handler:

let result = super::sdk_glue::block_on(
    client.some_resource.some_method(args),
)?;

Use typed models for request/response serialization:

use petstore_api_sdk::api::*;

4. Authentication

Custom commands automatically inherit the CLI's authentication. The following auth schemes are configured:

• Bearer (bearer): env PETSTORE_TOKEN

No manual auth wiring is needed in custom command handlers.

Regeneration Safety

File	Regenerated?	Notes
cli/petstore-api/custom.rs	No	Protected by .fernignore
cli/petstore-api/sdk_glue.rs	Yes	Bridges AppContext → SDK client
cli/petstore-api/main.rs	Yes	Calls custom::register(app)
petstore-api-sdk/	Yes	Co-generated typed SDK crate
petstore-api-types/	Yes	Co-generated typed models

After running fern generate, your custom.rs is preserved. All generated code (SDK, types, glue, main.rs) is updated to match the latest API spec. If the SDK surface changes (renamed methods, new sub-clients), update your custom.rs to match.

Build & Test

# Build the CLI (includes custom commands)
cargo build

# Run your custom command
petstore-api <your-command> [args]

# Run with verbose output for debugging
RUST_LOG=debug petstore-api <your-command> [args]