dol

Build a dol store: wrap any storage backend (files, S3, DB, dict, an API) behind a uniform dict-like (MutableMapping) interface, adding key and value transforms/serialization. Use when a user wants to give a backend a dict interface, add JSON/pickle/gzip (or custom) serialization to a store, transform or filter keys, compose codecs, cache a slow store, or asks 'how do I use dol to ...'. Covers wrap_kvs (the core), the ValueCodecs/KeyCodecs namespaces, Pipe composition, the ready-made file stores (Files/TextFiles/JsonFiles/PickleFiles), filt_iter, the test-with-dict-then-swap-backend workflow, and self-aware transforms via FirstArgIsMapping. For authoring interactive scaffolds see the /new-store, /add-codec, /explain-store commands; for modifying dol's internals see dol-dev-wrap-kvs.

Understand and safely modify dol's core wrapping machinery — wrap_kvs, store_decorator, Store.wrap, and how transforms are applied. Use when touching dol/trans.py or dol/base.py; when changing how key/value transforms (key_of_id, id_of_key, obj_of_data, data_of_obj, postget, preset) are called; when a transform passed to wrap_kvs behaves unexpectedly (called with/without the store as first arg); when working Issues #9/#12/#18/#6/#5; or when a wrap_kvs change could ripple through the ~32 ecosystem packages that use it. Covers the signature-conditioning rule (name AND arity), the FirstArgIsMapping marker, the delegation (has-a) architecture and its 'self is unwrapped' trap, the subclass-signature-freeze trap, and the mandatory dependents test-gate. For end-user store-building, see the consumer skills; for Windows path issues, see dol-dev-portability.

Keep dol working on Windows as well as Linux/macOS. Use when touching dol's path/key machinery (filesys.py, naming.py, paths.py, util.py), compiling regexes from templates/paths, mapping keys<->filesystem paths, or when a dol test/doctest passes on Linux/macOS but fails on the Windows CI job. Covers dol's specific landmines: safe_compile is path-only (never compile a regex with it), escape template LITERALS not the whole pattern, os.sep consistency in prefix/affix codecs, empty-prefix handling, POSIX-only os calls, and dol's native-separator key convention. For general cross-platform Python principles, see the global `cross-platform-python` skill.