fix: add recursion guard to StreamSlicerMeta.__instancecheck__

[devin-ai-integration]

Summary

StreamSlicerMeta.__instancecheck__ could cause a RecursionError when isinstance() was called on objects that have a wrapped_slicer attribute combined with a custom __getattr__ that delegates to the wrapped object. The original implementation used hasattr(instance, "wrapped_slicer"), which invokes __getattr__—and if that __getattr__ triggers further isinstance() checks (directly or indirectly), infinite recursion results.

Two changes fix this:

1. Recursion guard: A thread-local set tracks in-progress id(instance) values. On re-entry for the same object, we fall back to super().__instancecheck__().
2. object.__getattribute__ instead of hasattr: Bypasses any custom __getattr__ on the instance, so only objects with a real wrapped_slicer attribute (not a delegated one) trigger the unwrap path.

Resolves https://github.com/airbytehq/oncall/issues/11900:

• https://github.com/airbytehq/oncall/issues/11900

Review & Testing Checklist for Human

• Verify object.__getattribute__ semantics: The old code used hasattr, which also matched attributes returned by __getattr__. The new code only matches attributes in the instance __dict__ or class hierarchy. Confirm this is the correct behavior—StreamSlicerTestReadDecorator stores wrapped_slicer as a dataclass field (in __dict__), so it should still be found.
• Thread safety of _checking: _checking is a single threading.local instance on the metaclass, shared by all classes using StreamSlicerMeta. Verify that concurrent isinstance() calls from different threads cannot corrupt each other's in_progress sets.
• Run the full test suite (not just the decorator tests) to confirm no regressions in isinstance behavior across ConcurrentDeclarativeSource and other callers that rely on this metaclass.

Notes

• The three new tests cover: custom __getattr__ with wrapped_slicer (primary bug reproduction), nested/double-wrapped decorators, and a self-referencing cycle (pathological guard test).
• All 8 existing + new tests pass locally; ruff and mypy clean.

Link to Devin session: https://app.devin.ai/sessions/36ab5b8f87bf4f0991dc9a05c10781fc

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring

[github-actions]

👋 Greetings, Airbyte Team Member!

Here are some helpful tips and reminders for your convenience.

💡 Show Tips and Tricks

Testing This CDK Version

You can test this version of the CDK using the following:

# Run the CLI from this branch:
uvx 'git+https://github.com/airbytehq/airbyte-python-cdk.git@devin/1775527410-fix-recursion-error-stream-slicer-meta#egg=airbyte-python-cdk[dev]' --help

# Update a connector to use the CDK from this branch ref:
cd airbyte-integrations/connectors/source-example
poe use-cdk-branch devin/1775527410-fix-recursion-error-stream-slicer-meta

PR Slash Commands

Airbyte Maintainers can execute the following slash commands on your PR:

• /autofix - Fixes most formatting and linting issues
• /poetry-lock - Updates poetry.lock file
• /test - Runs connector tests with the updated CDK
• /prerelease - Triggers a prerelease publish with default arguments
• /poe build - Regenerate git-committed build artifacts, such as the pydantic models which are generated from the manifest JSON schema in YAML.
• /poe <command> - Runs any poe command in the CDK environment

📚 Show Repo Guidance

Helpful Resources

• CDK API Reference

📝 Edit this welcome message.

[devin-ai-integration]

This is a false positive. __instancecheck__ is a method on a metaclass (ABCMeta subclass), so its first parameter is the class being checked against, not an instance — cls is the correct name here. Using self would be misleading. The original code (introduced in #567) also used cls.

[github-actions]

PyTest Results (Fast)

4 015 tests  +3   4 004 ✅ +3   7m 40s ⏱️ -3s
    1 suites ±0      11 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 4a65149. ± Comparison against base commit 4aaafcf.

[github-actions]

PyTest Results (Full)

4 018 tests  +3   4 006 ✅ +3   11m 16s ⏱️ +17s
    1 suites ±0      12 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 4a65149. ± Comparison against base commit 4aaafcf.