acme-versioned-custom-commands

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How to author custom commands for the acme-versioned CLI using the co-generated SDK.

fern-api By fern-api schedule Updated 6/8/2026

name: acme-versioned-custom-commands description: How to author custom commands for the acme-versioned CLI using the co-generated SDK.

Custom Commands for acme-versioned

Overview

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

Adding a Custom Command

1. Edit cli/acme-versioned/custom.rs

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

use acme_versioned_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_glue::sdk_client(ctx);
            let result = super::sdk_glue::block_on(
                client.v1.get(id),
            )?;
            println!("{}", serde_json::to_string_pretty(&result).unwrap());
            Ok(())
        },
    );
    app
}

2. Available SDK Clients

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

Field Type Description
client.v1 acme_versioned_sdk::api::V1Client v1 operations
client.v2 acme_versioned_sdk::api::V2Client v2 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 acme_versioned_sdk::api::*;

4. Authentication

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

  • bearerAuth (bearer): env ACME_VERSIONED_TOKEN

No manual auth wiring is needed in custom command handlers.

Regeneration Safety

File Regenerated? Notes
cli/acme-versioned/custom.rs No Protected by .fernignore
cli/acme-versioned/sdk_glue.rs Yes Bridges AppContext → SDK client
cli/acme-versioned/main.rs Yes Calls custom::register(app)
acme-versioned-sdk/ Yes Co-generated typed SDK crate
acme-versioned-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
acme-versioned <your-command> [args]

# Run with verbose output for debugging
RUST_LOG=debug acme-versioned <your-command> [args]
Install via CLI
npx skills add https://github.com/fern-api/fern --skill acme-versioned-custom-commands
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