fix(collections): re-raise non-404 errors from async Collection.exists() (#2100)

[Anai-Guo]

Fixes #2100

Problem

CollectionAsync.exists() still had a bare catch-all:

async def exists(self) -> bool:
    try:
        await self.config.get(simple=True)
        return True
    except Exception:
        return False

so a connection error, auth failure or timeout is indistinguishable from "collection not found". The common guard

if not await collection.exists():
    await client.collections.create(...)

therefore tries to re-create the collection whenever the server is merely unreachable, masking the outage.

#1799 reported exactly this. #1950 fixed the sync path in weaviate/collections/collection/sync.py but the async counterpart was never updated.

Change

Mirror the sync implementation exactly — return False on 404, re-raise everything else:

except UnexpectedStatusCodeError as e:
    if e.status_code == 404:
        return False
    raise e

Test

Adds test_async_collection_exists to mock_tests/test_collection.py, following the existing test_collection_exists shape and the use_async_with_local pattern already used in mock_tests/test_auth.py. It asserts both branches: 404 → False, 500 → UnexpectedStatusCodeError with status_code == 500.

Verified locally against the mock server:

	new test	full mock_tests/test_collection.py
main (ae327ca), test only	FAILED — DID NOT RAISE UnexpectedStatusCodeError	—
with this fix	passed	21 passed

ruff / ruff format (pinned v0.14.7) and flake8 are clean on both touched files.

🤖 Generated with Claude Code

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

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