Authoring a mold

This page covers what's specific to the fimod-powered registry. For writing molds in general, see the official fimod documentation:

• Authoring molds guide
• Reference

Registry structure

Each mold in fimod-powered follows this layout:

molds/my_mold/
├── my_mold.py             # Must export transform()
├── templates/             # Jinja2 templates (optional)
│   └── template.j2
└── README.md              # Usage, examples, args documentation

test-molds/my_mold/
├── basic.input.json       # Input file
├── basic.expected.json    # Expected output
└── basic.run-test.toml    # Optional test config

The mold filename must match the directory name.

README.md

Every mold must include a README.md. This is what generates the mold's documentation page on this site. Use the existing molds as reference — dockerfile and poetry_migrate are good examples.

A typical README includes:

• Usage — one or two fimod s command examples
• Args — table of --arg options (if any)
• How it works — brief explanation of the approach

Conventions

• The module docstring ("""...""") is shown by fimod mold list — keep it to one line
• Use msg_warn() for non-fatal issues, gk_fail() for validation failures
• Prefer def transform(data, args, **_): — only declare env/headers if you use them