Discriminated Union With Nested Oneof Custom Commands

Custom Commands for discriminated-union-with-nested-oneof

Overview

The discriminated-union-with-nested-oneof 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/discriminated-union-with-nested-oneof/custom.rs    ← Your command handlers (protected by .fernignore)
cli/discriminated-union-with-nested-oneof/sdk.rs       ← Generated bridge: client() + block_on()
cli/discriminated-union-with-nested-oneof/main.rs      ← Generated entrypoint (calls custom::register)
discriminated-union-with-nested-oneof-sdk/             ← Co-generated typed SDK crate
discriminated-union-with-nested-oneof-types/           ← Co-generated typed model crate

Adding a Custom Command

1. Edit cli/discriminated-union-with-nested-oneof/custom.rs

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

use discriminated_union_with_nested_oneof_sdk::api::*;

pub fn register(app: CliApp) -> CliApp {
    let app = app.command(
        clap::Command::new("my-command")
            .about("Description of your command")
            .arg(clap::Arg::new("id").required(true)),
        |matches, ctx| {
            let id = matches.get_one::<String>("id").unwrap();
            let client = super::sdk::client(ctx);
            let result = super::sdk::block_on(
                client.resource.get(id),
            )?;
            println!("{}", serde_json::to_string_pretty(&result).unwrap());
            Ok(())
        },
    );
    app
}

2. Available SDK Clients

The super::sdk::client(ctx) call returns a discriminated_union_with_nested_oneof_sdk::api::Client with the following sub-clients:

(Sub-clients are derived from the API spec at generation time.)

3. Key Patterns

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

let client = super::sdk::client(ctx);

Run an async SDK call from a sync handler:

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

Use typed models for request/response serialization:

use discriminated_union_with_nested_oneof_sdk::api::*;

Regeneration Safety

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
discriminated-union-with-nested-oneof <your-command> [args]

# Run with verbose output for debugging
RUST_LOG=debug discriminated-union-with-nested-oneof <your-command> [args]