Andrew Browne

This commit prepares for the **release of `google-cloud-pubsub` version 2.35.0**, a **maintenance update** for the **Python client library**. It introduces a **new `AIInference MessageTransform` type** to the Pub/Sub API, enhancing message processing capabilities. Additionally, this release includes **various documentation updates** for several Pub/Sub API fields and updates internal versioning files such as `gapic_version.py` and `snippet_metadata_google.pubsub.v1.json` to reflect the new version.

This commit introduces a **new capability** to the **`google-cloud-pubsub` library** by adding the `AIInference` message transform type. This **feature** expands the `MessageTransform` functionality, enabling AI-driven processing of messages within Pub/Sub. Concurrently, the commit includes several **documentation updates** across the Pub/Sub API, clarifying field behaviors, adding resource tag links, and annotating `IDENTIFIER` fields for improved developer understanding. These changes are part of a routine **Librarian generation** to keep the client library synchronized with the latest proto definitions.

This commit primarily focuses on **maintenance updates** and **refactoring** within the `google-cloud-pubsub` package. It bumps several test dependencies, including `pytest`, `google-cloud-bigquery`, and `google-cloud-storage`, and upgrades the GitHub Actions `checkout` action to v6 in the lint workflow, enhancing the **development environment stability**. Additionally, it **refactors** the **Python Pub/Sub samples** in `publisher.py` and `subscriber.py` to improve clarity by consistently appending `'-smt'` to topic and subscription IDs in `create_topic_with_smt` and `create_subscription_with_smt` calls. Corresponding **test files** like `publisher_test.py` and `subscriber_test.py` were updated to align with these new naming conventions, ensuring consistency across the sample suite and improving **sample code readability** for users.

This commit **removes official support for Python 3.7 and 3.8** from the **google-cloud-pubsub** library. As a **maintenance chore**, it updates various **CI/CD workflows, documentation, build scripts, and test configurations** to reflect this change, including removing Python 3.7/3.8 from test matrices, updating dependency constraints, and adjusting `mypy` and `pytest` configurations. This change streamlines development by focusing on newer Python versions (3.9+), meaning users on Python 3.7 or 3.8 will need to upgrade their environment or use a previous library release.

This commit **fixes** an issue within the **`google-cloud-pubsub` package's test suite** by configuring `pytest.ini` to **ignore `FutureWarning`s**. Specifically, it suppresses warnings originating from `google.api_core` that pertain to Python version support. This **maintenance improvement** ensures cleaner test output, allowing developers to focus on critical test failures without distraction from benign, environment-specific warnings.

This commit introduces a **new capability** for enhanced **debugging and observability** within the **Google Cloud Pub/Sub subscriber client library**. Extensive **debug logging** has been added to critical components, including the `streaming_pull_manager` and `message` acknowledgment/modification methods, to aid in **troubleshooting** message processing. Furthermore, `AckRequest` and `ModAckRequest` objects now include an optional `message_id` field, enabling more precise tracking of individual messages. These changes collectively improve the ability to diagnose subscriber behavior, supported by corresponding **test updates** to reflect the protocol modifications.

This **chore** commit focuses on **upgrading development dependencies** and **Python versions** within the **`google-cloud-pubsub` package**. It updates the Python version used for **linting** in **GitHub Actions workflows** and for **Nox sessions** (including `docs` and `docfx`) from 3.8 to 3.10. Additionally, it updates the versions of `pytest` and `google-cloud-bigquery` in the **snippet test requirements**, adjusting Python version conditions. This **maintenance work** ensures the **development environment** and **testing infrastructure** remain current and **compatible with newer Python releases**, specifically Python 3.10.

This commit **refines the logging behavior** within the **Google Cloud Pub/Sub subscriber client library**, specifically for events related to **streaming pull connection termination**. It **adjusts log severities** in `packages/google-cloud-pubsub/google/cloud/pubsub_v1/subscriber/_protocol/streaming_pull_manager.py`, downgrading messages from `exception` to `info` in `_on_exception` and from `error` to `debug` in `_should_terminate_stream`. This **logging refinement** addresses an issue where routine or expected stream termination events were reported with unnecessarily high severity. The change improves **observability and debugging** by reducing noise in application logs, ensuring that only genuinely problematic events trigger high-severity alerts.

This commit **fixes** an issue in the **`google-cloud-pubsub` library** where OpenTelemetry context was not correctly propagated to subscriber callbacks. It introduces context manager capabilities to `SubscribeOpenTelemetry` within `subscribe_opentelemetry.py`, allowing the `_wrap_callback_errors` function in the **streaming pull manager** to properly manage OpenTelemetry process spans around the callback execution. This **enhancement** ensures that distributed traces accurately reflect the full lifecycle of messages processed by **Pub/Sub subscribers**, significantly improving observability for users leveraging OpenTelemetry.

This commit introduces a **bug fix** to the **Pub/Sub subscriber's streaming pull protocol** by significantly enhancing its error handling capabilities. It ensures that **fatal stream errors** are properly surfaced to the future, allowing unrecoverable issues to explicitly terminate the stream and be reported. The change involves updating the error classification logic within `_should_terminate` and introducing a new `_on_fatal_exception` callback in `streaming_pull_manager.py` to manage these critical exceptions. This adjustment also refines the set of **retryable error codes**, leading to more robust and predictable subscriber behavior by preventing indefinite retries on unrecoverable errors.

This commit provides a **fix** and **enhancement** to the **`BackgroundConsumer`** class in the **`google.api_core.bidi`** module, enabling it to surface fatal exceptions to its caller. Previously, unhandled errors in the background processing thread could go unnoticed, but now an optional `on_fatal_exception` callback can be provided during initialization. This callback is invoked when an unhandled exception occurs within the `_thread_main` loop, allowing the main application to react to critical failures. This significantly improves the **error handling and observability** of long-running background tasks, preventing silent failures. Unit tests for `test_bidi.py` have been updated to cover this new functionality.

This **chore commit** updates the **automation configurations** for the **Google Cloud Pub/Sub client library**. It modifies `packages/google-cloud-pubsub/.github/blunderbuss.yml` to **change the default assignees for issues and pull requests to `abbrowne126`**. Concurrently, the `packages/google-cloud-pubsub/owlbot.py` configuration is updated to **exclude `blunderbuss.yml` from templated files**, removing a specific replacement rule for it. This **maintenance task** streamlines issue and PR management by reassigning default responsibility and refines OwlBot's templating scope for this specific configuration file.