| | """ |
| | Helpers related to (dynamic) resource retrieval. |
| | """ |
| |
|
| | from __future__ import annotations |
| |
|
| | from functools import lru_cache |
| | from typing import TYPE_CHECKING, Callable, TypeVar |
| | import json |
| |
|
| | from referencing import Resource |
| |
|
| | if TYPE_CHECKING: |
| | from referencing.typing import URI, D, Retrieve |
| |
|
| | |
| | _T = TypeVar("_T") |
| |
|
| |
|
| | def to_cached_resource( |
| | cache: Callable[[Retrieve[D]], Retrieve[D]] | None = None, |
| | loads: Callable[[_T], D] = json.loads, |
| | from_contents: Callable[[D], Resource[D]] = Resource.from_contents, |
| | ) -> Callable[[Callable[[URI], _T]], Retrieve[D]]: |
| | """ |
| | Create a retriever which caches its return values from a simpler callable. |
| | |
| | Takes a function which returns things like serialized JSON (strings) and |
| | returns something suitable for passing to `Registry` as a retrieve |
| | function. |
| | |
| | This decorator both reduces a small bit of boilerplate for a common case |
| | (deserializing JSON from strings and creating `Resource` objects from the |
| | result) as well as makes the probable need for caching a bit easier. |
| | Retrievers which otherwise do expensive operations (like hitting the |
| | network) might otherwise be called repeatedly. |
| | |
| | Examples |
| | -------- |
| | |
| | .. testcode:: |
| | |
| | from referencing import Registry |
| | from referencing.typing import URI |
| | import referencing.retrieval |
| | |
| | |
| | @referencing.retrieval.to_cached_resource() |
| | def retrieve(uri: URI): |
| | print(f"Retrieved {uri}") |
| | |
| | # Normally, go get some expensive JSON from the network, a file ... |
| | return ''' |
| | { |
| | "$schema": "https://json-schema.org/draft/2020-12/schema", |
| | "foo": "bar" |
| | } |
| | ''' |
| | |
| | one = Registry(retrieve=retrieve).get_or_retrieve("urn:example:foo") |
| | print(one.value.contents["foo"]) |
| | |
| | # Retrieving the same URI again reuses the same value (and thus doesn't |
| | # print another retrieval message here) |
| | two = Registry(retrieve=retrieve).get_or_retrieve("urn:example:foo") |
| | print(two.value.contents["foo"]) |
| | |
| | .. testoutput:: |
| | |
| | Retrieved urn:example:foo |
| | bar |
| | bar |
| | |
| | """ |
| | if cache is None: |
| | cache = lru_cache(maxsize=None) |
| |
|
| | def decorator(retrieve: Callable[[URI], _T]): |
| | @cache |
| | def cached_retrieve(uri: URI): |
| | response = retrieve(uri) |
| | contents = loads(response) |
| | return from_contents(contents) |
| |
|
| | return cached_retrieve |
| |
|
| | return decorator |
| |
|
