chore: Add SpannerMockServer

[bhatt4982]

• Code is combination of both python-spanner and python-spanner-sqlalchemy
• Added system tests for verification
• Added nox for project configuration and verification
• Added workflow to publish to PyPi

[gemini-code-assist]

Summary of Changes

Hello @bhatt4982, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new Python library, spannermockserver, designed to provide a lightweight, in-memory mock for Google Cloud Spanner. This mock server is crucial for enabling efficient and isolated testing of applications that interact with Spanner, eliminating the need for a live database connection during development and CI/CD. The changes encompass the core mock server logic, generated gRPC interfaces, comprehensive testing utilities, and robust project management tooling.

Highlights

• New Spanner Mock Server: Introduced a new Python library, spannermockserver, which provides an in-memory mock server for Google Cloud Spanner, enabling local testing without a live Spanner instance.
• Code Integration: The mock server's implementation combines logic and concepts from both the python-spanner and python-spanner-sqlalchemy projects.
• System Tests: Comprehensive system tests have been added to verify the functionality and correctness of the SpannerMockServer.
• Nox Configuration: Project configuration and verification are now managed using Nox, including sessions for formatting, linting, testing, gRPC code generation, and package building.
• PyPi Publishing Workflow: A new workflow has been established to facilitate publishing the spannermockserver library to PyPi.

Ignored Files

• Ignored by pattern: .github/workflows/** (1)
  • .github/workflows/release-spannermockserver.yml

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[bhatt4982]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a comprehensive mock server for Google Cloud Spanner, which is a valuable addition for facilitating testing. The implementation includes the core mock logic, gRPC service definitions, helper utilities for tests, and initial system tests. The code is generally well-structured. However, I've identified a critical bug in the mock Spanner logic that could lead to incorrect test behavior, along with some high-severity issues related to unreachable code from incorrect dictionary handling. I've also found several medium-severity issues in the noxfile.py configuration, such as using a non-existent Python version, inconsistent linting rules, and an undefined nox session. The suggested changes aim to fix these bugs and improve the robustness and maintainability of the new mock server.

[gemini-code-assist]

Code Review

This pull request introduces a new Python package spannermockserver, a lightweight in-memory mock server for Google Cloud Spanner. The package includes mock implementations for SpannerServicer and DatabaseAdminServicer, along with a noxfile.py for project automation and system tests for verification.

The overall structure is well-organized, and the use of a mock server for testing is a great practice. I've identified a few areas for improvement, primarily concerning potential bugs in the mock implementation and configuration inconsistencies. My main concerns are:

• A bug in mock_spanner.py that nullifies a transaction parameter.
• Unsafe dictionary access in the mock servicers that could lead to KeyError exceptions instead of graceful gRPC errors.
• Inconsistencies in the noxfile.py configuration for linting and session names.

I've provided specific suggestions to address these points. Once these are addressed, this will be a solid foundation for the mock server.

[olavloite]

LGTM, with some minor nits/requests. These can be picked up in follow-up PRs if that is easier.