Migrating from Typer

When this path fits

Use this path when typed Typer commands and dependency injection are already valuable. Install the optional adapter so Typer remains optional for Click-only consumers:

python -m pip install 'base-cli[typer]'

Incremental change

Before, Typer owns the process entry point:

import typer

app = typer.Typer()


@app.command()
def status(verbose: bool = typer.Option(False, "--verbose")) -> None:
    typer.echo("ready" if not verbose else "ready (verbose)")


if __name__ == "__main__":
    app()

After, retain the Typer declarations and attach the materialized command:

import base_cli
import typer

app = typer.Typer()


@app.command()
def status(verbose: bool = typer.Option(False, "--verbose")) -> None:
    context = base_cli.get_current_context()
    context.log.info("status requested")
    typer.echo("ready" if not verbose else "ready (verbose)")


command = base_cli.attach_typer(app, name="example")

if __name__ == "__main__":
    raise SystemExit(base_cli.run_app(command))

Typer remains responsible for decorators, type-driven parameters, nested apps, help, completion, dependency injection, and Typer/Click exceptions. The adapter returns Typer's generated Click command; base-cli owns the lifecycle, context, logging, redaction, runtime state, cleanup, history hooks, and output contracts. For custom configuration use base_cli.attach_typer(app, app=base_cli.App(...)).

Verification and rollback

• Test the supported Typer and Python matrix, including the vendored Click boundary used by newer Typer releases.
• Compare typed defaults, callback injection, help, completion, and exit codes with the original app.
• Add contract fixtures and exercise debug, quiet, JSON, and retained diagnostics.
• Keep the old Typer entry point available until the wheel-first pilot is green; restore it to roll back without rewriting command code.

See typer-adapter.md for adapter details.