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.claude/CLAUDE.md

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+# cw
+
+A codec layer wiring a string-only environment (the command line) to a Python
+function call: `argv -> Namespace -> (args, kwargs) -> f -> result -> stdout`.
+The MIT-licensed, in-house replacement for `argh` (LGPL-3.0-or-later).
+
+## Module map (`cw/`)
+
+- `base.py` — bottom of the import graph: sentinels, errors, help rendering.
+  Everything else imports from here.
+- `grammar.py` — **the riskiest, most opinionated module**: how a Python
+  signature becomes command-line arguments (reproduces argh 0.31.3's behavior
+  deliberately — see `docs/adr/0004-grammar-errata.md`).
+- `ingress.py` — `Namespace -> (args, kwargs)`, honouring `/`, `*args`, `*`, `**kwargs`.
+- `egress.py` — `result -> stdout lines + exit code` — a seam argh has **no
+  hook for at all**.
+- `cli.py` — the argparse surface: build a parser, run one; produces a **plain**
+  `argparse.ArgumentParser`, never a subclass (so `argcomplete.autocomplete`
+  and other argparse-typed tools keep working).
+- `commands.py` — turns an object (function, list, mapping, module, instance,
+  or `'pkg.mod:name'` string) into the `{name: callable}` tree a parser is
+  built from.
+- `convention.py` — `cw`'s defaults, one frozen value per context.
+- `resolution.py` — resolves function specs from various formats; `resource_inputs`
+  needs the `resource` extra (real `i2`, not the LGPL package cw replaces).
+- `compat.py` — **deprecated from day one**: a transitional argh shim so a repo
+  can retire an `argh` dependency with a one-line import change.
+- `testing.py` — record a CLI's behaviour before a migration, assert it after;
+  deliberately standalone (only stdlib imports — see D4 in the ADRs).
+
+## Tests & lint (verified)
+
+```bash
+uv venv .venv && uv pip install -e ".[dev]"
+.venv/bin/pytest -v --tb=short   # 972 passed, 2 skipped, 1 environment-dependent failure (see gotcha)
+.venv/bin/ruff check .
+```
+Or `wads ci-local` (`[tool.wads.ci.install].extras = "test"` — **required**: a
+bare `uv pip install -e .` leaves `cw.resolution`'s i2-dependent tests/doctests
+failing).
+
+**Gotcha found verifying:** `tests/argh_parity/test_compat_parity.py::TestArgDeclarations::test_completer_reaches_the_action`
+failed locally — it asserts on real `argh`'s own parser action gaining a
+`.completer` attribute, which didn't happen in this environment (argh version/
+`argcomplete` availability), not a `cw` bug. `tests/argh_parity/` is a
+differential suite (cw vs. real argh) that self-skips when `argh` is absent;
+`cw` itself never imports `argh` at runtime — `test_import_is_cheap.py` enforces
+that import costs stdlib only.
+
+## Docs
+
+- `docs/adr/0001`-`0008`: the v1 seam table, ingress stash, merge ladder, grammar
+  errata, release/rollback policy, v1 cut list, what adversarial review changed,
+  no-fourth-channel-for-group-kwargs.
+
+## Dependents
+
+41 packages import `cw` (fleet dependency graph), including `appshelf`,
+`astern`, `crowsnest`, `liaise`, `openloops`, `priv`, `wads` — see
+`fleet_dependents.json` for the full list. Check dependents' CLI tests before
+changing `grammar.py`, `ingress.py`, or `egress.py`'s public behaviour.