Write an extractor script

§ 1Purpose

Automate one machine-derivable slice of the WAD so it stays honest against its source of truth.

§ 2Prerequisites

• uv installed
• A source of truth worth automating (CI config, build metadata, a database, an API)

§ 3Flowchart

§ 4Steps

One script = one output file = one source of truth. Name it extract_<thing>.py; its output is data/generated/<thing>.wcl.

Copy extractor_template.py (bundled with this skill; extract_repo.py ships in every scaffold). Set the PEP 723 header's dependencies for whatever the source needs (pyyaml, a DB driver, httpx…).

Decide which block kinds the findings become (relations? pipeline stages? a code_item :db_schema with db_table/db_column children?). When the data genuinely fits no base family, declare a typed custom block in schema/extensions.wcl and emit that instead, adding a matching render to the book template — better a first-class block than data contorted into the wrong shape. Anything needing human naming — like source name → WAD container id — goes in a small in-script table, so customising the mapping is editing data, not logic.

Banner comment first, namespace wcl.wad, then blocks — collections sorted, ids derived from source names, no timestamps. Full overwrite of the one output file; an empty result still writes the banner.

Add the one import "./<thing>.wcl" line in data/generated/main.wcl (once, committed). Run the script twice — the second run must be byte-identical — then wcl check and render. If the extractor replaces hand-authored blocks, delete those and leave a comment pointing at the script.