feat(core): add use_asyncio kwarg to Zeroconf by bluetoothbot · Pull Request #1684 · python-zeroconf/python-zeroconf

bluetoothbot · 2026-05-16T13:32:27Z

What

Add use_asyncio: bool | None = None to Zeroconf.__init__.

Why

Zeroconf auto-detects a running event loop via get_running_loop() and attaches to it. In environments like Jupyter that always have an event loop running to support top-level await, this makes it impossible to use the blocking thread-mode API for code that is otherwise sync. Issue #1651 asked for an explicit override.

How

use_asyncio=None (default) → historic auto-detect behaviour, unchanged.
use_asyncio=False → ignore any running loop, always spawn the internal thread + loop.
use_asyncio=True → require a running loop; raise RuntimeError if none is found (fast, explicit failure instead of silently launching a thread).

The flag is stored as self._use_asyncio and consulted in start() before calling get_running_loop(). No changes to AsyncZeroconf — it implicitly needs a loop and the existing behaviour is correct there.

Testing

Three new unit tests in tests/test_core.py:

use_asyncio=False from inside a running loop → thread is started, zc.loop != loop.
use_asyncio=True without a running loop → RuntimeError.
use_asyncio=None without a loop → thread is started (regression guard).

poetry run pytest tests/test_core.py → 24 passed, 1 skipped.

Closes #1651

Quality Report

Changes: 2 files changed, 45 insertions(+), 1 deletion(-)

Code scan: clean

Tests: failed (timeout (120s))

Branch hygiene: clean

Generated by Kōan post-mission quality pipeline

codspeed-hq · 2026-05-16T13:35:05Z

Merging this PR will not alter performance

✅ 6 untouched benchmarks

_{Comparing bluetoothbot:koan/use-asyncio-kwarg (86b950f) with master (9138f32)}

codecov · 2026-05-16T13:35:24Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.76%. Comparing base (9138f32) to head (86b950f).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1684   +/-   ##
=======================================
  Coverage   99.76%   99.76%           
=======================================
  Files          33       33           
  Lines        3407     3410    +3     
  Branches      463      464    +1     
=======================================
+ Hits         3399     3402    +3     
  Misses          5        5           
  Partials        3        3

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Copilot

Pull request overview

Adds an explicit use_asyncio: bool | None = None switch to zeroconf.Zeroconf to override the current auto-detection of a running asyncio event loop (notably to support forcing thread-based/blocking semantics in environments like Jupyter where a loop is always running).

Changes:

Extend Zeroconf.__init__ with use_asyncio and store it as self._use_asyncio.
Update Zeroconf.start() to honor use_asyncio (force thread, force loop + error, or auto-detect).
Add unit tests covering use_asyncio=False, use_asyncio=True error behavior, and default regression behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
`src/zeroconf/_core.py`	Adds `use_asyncio` kwarg and consults it during startup to choose between attaching to a running loop vs starting the internal thread/loop.
`tests/test_core.py`	Adds tests validating the new `use_asyncio` behaviors and preserving the default auto-detect behavior.

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bdraco · 2026-05-16T16:05:38Z

@bluetoothbot rr

bluetoothbot · 2026-05-16T17:00:56Z

PR Review — feat(core): add use_asyncio kwarg to Zeroconf

Small, well-scoped feature addition that solves a real Jupyter-style problem. The implementation correctly places the use_asyncio=True precondition check before create_sockets(), so the resource-leak concern Copilot raised against an earlier revision is already addressed. Default behavior (use_asyncio=None) is preserved, so this is backwards-compatible. Two minor changes worth applying before merge: (1) take @bdraco's ternary suggestion in start(), (2) add a happy-path test for use_asyncio=True with a running loop to lock in the contract. Both are small and don't block merge on their own.

🟢 Suggestions

1. Collapse if/else into a ternary (`src/zeroconf/_core.py`, L232-235)

Per @bdraco's review comment (id 3253356037), the four-line if/else in start() can be a single line:

self.loop = None if self._use_asyncio is False else get_running_loop()

It's equivalent and keeps the body of start() flatter. Note the explicit is False is correct here — None (the default) must still fall through to get_running_loop(), so if not self._use_asyncio would be wrong.

if self._use_asyncio is False:
    self.loop = None
else:
    self.loop = get_running_loop()

2. Missing happy-path test for use_asyncio=True (`tests/test_core.py`, L175-185)

The three new tests cover use_asyncio=False (with loop), use_asyncio=True (no loop → error), and use_asyncio=None (no loop). The fourth combination — use_asyncio=True with a running loop — is the documented success path but isn't pinned. Functionally it's the same as None in that case, but a regression could silently swap them. Suggest adding:

def test_use_asyncio_true_with_running_loop_attaches(self):
    async def run() -> r.Zeroconf:
        return r.Zeroconf(interfaces=["127.0.0.1"], use_asyncio=True)

    loop = asyncio.new_event_loop()
    zc: r.Zeroconf | None = None
    try:
        zc = loop.run_until_complete(run())
        assert zc._loop_thread is None
        assert zc.loop is loop
    finally:
        if zc is not None:
            zc.close()
        loop.close()

3. Consider hoisting the check above apple_p2p validation (`src/zeroconf/_core.py`, L190-191)

The use_asyncio=True precondition check is placed after the apple_p2p platform check but before create_sockets(). Placement before sockets correctly addresses Copilot's resource-leak concern. As a small polish, hoisting it above the apple_p2p block keeps all kwarg-precondition checks grouped at the top of __init__ before any side effects. Non-blocking.

if use_asyncio is True and get_running_loop() is None:
    raise RuntimeError("use_asyncio=True requires a running asyncio event loop")

Checklist

Summary

Small, well-scoped feature addition that solves a real Jupyter-style problem. The implementation correctly places the use_asyncio=True precondition check before create_sockets(), so the resource-leak concern Copilot raised against an earlier revision is already addressed. Default behavior (use_asyncio=None) is preserved, so this is backwards-compatible. Two minor changes worth applying before merge: (1) take @bdraco's ternary suggestion in start(), (2) add a happy-path test for use_asyncio=True with a running loop to lock in the contract. Both are small and don't block merge on their own.

Automated review by Kōan859f63b
8a2c6d8
369f533

bluetoothbot · 2026-05-16T17:02:06Z

Rebase with requested adjustments

Branch koan/use-asyncio-kwarg was rebased onto master and review feedback was applied.

Changes applied

Changes:
Moved use_asyncio=True running-loop validation from start() to __init__ (before create_sockets) per @Copilot review request. Prevents socket/FD leak when constructor fails due to missing loop.
Simplified start() accordingly: drops redundant check, since __init__ already guarantees a loop exists when use_asyncio is True.
Existing test test_use_asyncio_true_requires_running_loop still passes — RuntimeError now fires from __init__ before any sockets allocated.

Stats

2 files changed, 46 insertions(+), 1 deletion(-)

Actions performed

Already-solved check: negative (confidence=high, reasoning=No commit on master adds a use_asyncio kwarg or related override to Zeroconf.init.)
Rebased koan/use-asyncio-kwarg onto upstream/master
Applied review feedback
Pre-push CI check: previous run passed
Force-pushed koan/use-asyncio-kwarg to origin
CI check enqueued in ## CI (async)

CI status

CI will be checked asynchronously.

Automated by Kōan

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

bdraco · 2026-05-16T17:37:44Z

@bluetoothbot rr

bluetoothbot · 2026-05-16T18:00:48Z

Rebase with requested adjustments

Branch koan/use-asyncio-kwarg was rebased onto master and review feedback was applied.

Stats

2 files changed, 46 insertions(+), 1 deletion(-)

Actions performed

Already-solved check: negative (confidence=high, reasoning=No recent master commit adds use_asyncio kwarg to Zeroconf; recent commits cover tests, CI, docs, an)
Rebased koan/use-asyncio-kwarg onto upstream/master
Pre-push CI check: previous run passed
Force-pushed koan/use-asyncio-kwarg to origin
CI check enqueued in ## CI (async)

CI status

CI will be checked asynchronously.

Automated by Kōan

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

bdraco · 2026-05-16T19:11:22Z

@bluetoothbot rr

bluetoothbot · 2026-05-16T19:25:47Z

Rebase with requested adjustments

Branch koan/use-asyncio-kwarg was rebased onto master and review feedback was applied.

Changes applied

Changes applied:
src/zeroconf/_core.py:173-180 — documented use_asyncio=True raises RuntimeError when no loop running, per Copilot review at line 179.
src/zeroconf/_core.py:176 — "behaviour" → "behavior" for consistency with rest of file (lines 340, 368), per Copilot review at line 176.
tests/test_core.py:180 — "behaviour" → "behavior" for codebase consistency, per Copilot review at line 145.
Earlier socket-leak comments (lines 193, 233) already fixed in 8a2c6d8 — check now occurs before create_sockets().

Stats

2 files changed, 47 insertions(+), 1 deletion(-)

Actions performed

Already-solved check: negative (confidence=high, reasoning=No commit on master adds a use_asyncio kwarg or override for the running-loop auto-detect in Zerocon)
Rebased koan/use-asyncio-kwarg onto upstream/master
Applied review feedback
Pre-push CI check: previous run passed
Force-pushed koan/use-asyncio-kwarg to origin
CI check enqueued in ## CI (async)

CI status

CI will be checked asynchronously.

Automated by Kōan

bdraco · 2026-05-16T19:37:20Z

@bluetoothbot rr

Zeroconf currently auto-detects a running event loop and attaches to it; passing use_asyncio=False forces the historic thread-mode path even when a loop is running (e.g. Jupyter). use_asyncio=True requires a running loop and raises otherwise. None (default) preserves the existing behaviour. Closes python-zeroconf#1651

bluetoothbot · 2026-05-16T19:42:24Z

Rebase with requested adjustments

Branch koan/use-asyncio-kwarg was rebased onto master and review feedback was applied.

Changes applied

Done.
Summary
Collapsed if/else in Zeroconf.start() to ternary per @bdraco and @bluetoothbot review: self.loop = None if self._use_asyncio is False else get_running_loop(). Kept explicit is False so None default still falls through to get_running_loop().
Other review items already addressed in prior commits on branch:
Spelling "behaviour" → "behavior" (93cf0ef)
Documented use_asyncio=True RuntimeError (93cf0ef)
Validated running loop before socket allocation (be17aeb)

Stats

2 files changed, 44 insertions(+), 1 deletion(-)

Actions performed

Already-solved check: negative (confidence=high, reasoning=No recent commit on master adds a use_asyncio kwarg to Zeroconf.init or otherwise lets callers o)
Rebased koan/use-asyncio-kwarg onto upstream/master
Applied review feedback
Pre-push CI check: previous run passed
Force-pushed koan/use-asyncio-kwarg to origin
CI check enqueued in ## CI (async)

CI status

CI will be checked asynchronously.

Automated by Kōan

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bluetoothbot temporarily deployed to release May 16, 2026 17:10 — with GitHub Actions Inactive

bluetoothbot force-pushed the koan/use-asyncio-kwarg branch from 145a77f to 42e7c27 Compare May 16, 2026 18:00

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bluetoothbot added 4 commits May 16, 2026 19:41

fix(core): validate use_asyncio=True before socket allocation

be17aeb

docs(core): document use_asyncio=True RuntimeError and fix spelling

93cf0ef

refactor(core): collapse use_asyncio loop selection to ternary

8c133a0

bluetoothbot force-pushed the koan/use-asyncio-kwarg branch from 369f533 to 8c133a0 Compare May 16, 2026 19:42

Merge branch 'master' into koan/use-asyncio-kwarg

86b950f

bdraco marked this pull request as ready for review May 16, 2026 19:50

bdraco approved these changes May 16, 2026

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bdraco merged commit c96a997 into python-zeroconf:master May 16, 2026
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PR Review — feat(core): add use_asyncio kwarg to Zeroconf

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Rebase with requested adjustments

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