Write a pre-prompt hook

Write a pre-prompt hook#

A pre_prompt hook runs before the interactive prompts are shown to the user. Use it to check preconditions—for example, required system tools, network access, or minimum software versions. If the hook raises an exception or exits with a non-zero status, Cookieplone aborts cleanly before asking any questions.

Create the hook file#

Inside your template directory, create a hooks/ directory and add pre_prompt.py:

my-template/
└── templates/
    └── myproject/
        ├── cookieplone.json
        ├── hooks/
        │   └── pre_prompt.py
        └── {{cookiecutter.project_slug}}/
            └── ...

Check for a required tool#

# hooks/pre_prompt.py
import shutil
import sys


def check_git():
    if shutil.which("git") is None:
        print("ERROR: git is required but not found on PATH.")
        sys.exit(1)


if __name__ == "__main__":
    check_git()

Cookieplone runs this script with the Python interpreter that runs Cookieplone itself, in a temporary copy of the template directory. A non-zero exit code makes Cookieplone print the hook's output, followed by:

Sanity checks failed.
Please review the errors above and try again.

Cookieplone then exits without asking any question.

Check a minimum Python version#

The hook runs with the interpreter that runs Cookieplone, so sys.version_info describes that interpreter, not a Python the generated project may use later:

# hooks/pre_prompt.py
import sys

MINIMUM_PYTHON = (3, 10)

if sys.version_info < MINIMUM_PYTHON:
    print(
        f"ERROR: Python {MINIMUM_PYTHON[0]}.{MINIMUM_PYTHON[1]} or later is required. "
        f"You are running {sys.version}."
    )
    sys.exit(1)

Raise a clean failure#

Calling sys.exit(1) produces a clean exit with a message. Do not raise unhandled exceptions; they produce a noisy traceback that obscures the real reason for the failure.

When pre_prompt hooks run#

The pre_prompt hook runs after the template repository is resolved and cloned, but before the interactive wizard starts. It does not receive the user's answers because none have been collected yet. For the same reason, Cookieplone doesn't render it with Jinja2: an expression such as {{ cookiecutter.project_slug }} in the script stays as written. It also runs with --no-input, and on every re-run over an existing project.

See Hooks for the other hooks and how failures are handled.

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