sniffio 1.3.1: detect current async library using sniffio.current_async_library

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: detect current async library using sniffio.current_async_library
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:pypi/sniffio@1.3.1
Demonstrate these symbols/APIs:
  - sniffio.AsyncLibraryNotFoundError
  - sniffio.current_async_library
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:55ffb2641ebf5df35f7beb73829db0c6b52a96ec0f22a011b905cbc1e598fc5c","constraints":{"executionContext":"python"},"contract":["assert current_async_library raises AsyncLibraryNotFoundError when called outside async context","assert current_async_library returns asyncio when called inside asyncio.run coroutine","assert current_async_library returns the name set via current_async_library_cvar","assert AsyncLibraryNotFoundError is a subclass of RuntimeError"],"goal":"detect current async library using sniffio.current_async_library","kind":"HOW","packages":["pkg:pypi/sniffio@1.3.1"],"schemaVersion":1,"symbols":["sniffio.AsyncLibraryNotFoundError","sniffio.current_async_library"]},"contractCommand":["python3","test/contract.py"],"environment":{"arch":"x64","distro":"alpine","ecosystem":"pypi","executionContext":"python","language":"python","libc":"musl","moduleSystem":"standard","os":"linux","osVersionBucket":"24","packageManager":"pip","packageManagerVersion":"24.0","runtime":"python","runtimeVersion":"3.12","schemaVersion":1},"license":"MIT-0","packages":["pkg:pypi/sniffio@1.3.1"],"schemaVersion":1,"subject":"pkg:pypi/sniffio@1.3.1","symbols":["sniffio.AsyncLibraryNotFoundError","sniffio.current_async_library"],"verifierAdapter":"python@1"}

[project]
name = "verify-sniffio"
version = "0.1.0"
dependencies = [
    "sniffio==1.3.1",
]

sniffio==1.3.1

{
  "schemaVersion": 1,
  "goal": "detect current async library using sniffio.current_async_library",
  "kind": "HOW",
  "packages": [
    "pkg:pypi/sniffio@1.3.1"
  ],
  "symbols": [
    "sniffio.AsyncLibraryNotFoundError",
    "sniffio.current_async_library"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

import asyncio
import sniffio
from sniffio import current_async_library, AsyncLibraryNotFoundError, current_async_library_cvar


def test_no_async_library_raises():
    try:
        current_async_library()
        assert False, "current_async_library should raise AsyncLibraryNotFoundError outside async context"
    except AsyncLibraryNotFoundError as exc:
        assert isinstance(exc, RuntimeError)


def test_asyncio_detection():
    async def get_lib():
        return current_async_library()

    result = asyncio.run(get_lib())
    assert result == "asyncio"


def test_context_variable_override():
    token = current_async_library_cvar.set("custom_engine")
    try:
        assert current_async_library() == "custom_engine"
    finally:
        current_async_library_cvar.reset(token)


def test_exception_type_hierarchy():
    assert issubclass(AsyncLibraryNotFoundError, RuntimeError)
    err = AsyncLibraryNotFoundError("no async library detected")
    assert str(err) == "no async library detected"


def main():
    test_no_async_library_raises()
    test_asyncio_detection()
    test_context_variable_override()
    test_exception_type_hierarchy()
    print("All contract assertions passed.")


if __name__ == "__main__":
    main()