feat(storage): add object contexts in Go GCS SDK

[krishnamd-jkp]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @krishnamd-jkp, 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 enhances the Go Google Cloud Storage SDK by introducing support for object contexts. This new feature allows users to associate custom key-value metadata with their objects, providing a flexible way to annotate and categorize data. Furthermore, it enables powerful filtering capabilities during object listing, allowing users to retrieve objects based on the presence, absence, or specific values of these custom contexts. The changes involve new data structures, conversion logic, and integration into existing client operations like create, update, copy, compose, and list.

Highlights

• New Object Contexts Feature: Introduced ObjectContexts and ObjectContextValue types to allow users to attach custom key-value metadata to Google Cloud Storage objects.
• API Integration: Updated ObjectAttrsToUpdate and ObjectAttrs to include the new Contexts field, enabling context management during object creation, updates, copies, and compositions.
• Filtering Capabilities: Added a CustomContext field to the Query struct, allowing objects to be filtered based on the presence, absence, or specific key-value pairs of their custom contexts during list operations.
• Client Implementation: Modified both gRPC and HTTP clients (grpc_client.go, http_client.go) to support the new context functionality for listing and updating objects.
• Comprehensive Testing: Added extensive unit and integration tests (contexts_test.go, integration_test.go) to ensure the correct behavior of object contexts across various operations, including handling Unicode characters and context deletion.

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[gemini-code-assist]

Code Review

This pull request introduces support for object contexts in the Go GCS SDK, a significant feature enhancement. The changes include new types for object contexts, conversion functions for different API layers (raw/HTTP and proto/gRPC), and updates to client methods to handle these contexts. Extensive integration tests have been added to cover various scenarios like creation, patching, copying, and listing objects with contexts. The implementation is mostly solid, but I've identified a critical bug in filter string construction and an incorrect test case for object composition. I've also included several suggestions to improve code clarity and test robustness.

[cpriti-os]

Changes requested.

[tritone]

This has a bit of a smell to me. Is it a requirement to make a CustomContext type in each language which does this sort of cleverness? Or would it be easier to just expose Filter directly as a field on Query and allow the user to construct the appropriate filter string themself?

[krishnamd-jkp]

I introduced this to just make it user friendly. It wouldn't be user friendly to expect users to give the string themselves, would it? Given it has unintuitive format like providing "-" for negation, "key=value", "key:*" etc.

[tritone]

I think the place to introduce this kind of a structured format would generally be in the proto message definition rather than in the SDKs. Can you check how this is implemented in other languages and/or check in with the team doing the API launch to see what they think?

[tritone]

The Java API looks like it's just using filter as a text field directly so IMO it's also fine to do that in Go https://github.com/googleapis/java-storage/pull/3329/files#diff-20bcaa643fb27f1cb3b69cd788ade6590ecec05456217cc7103513ca3a89ba94

[cpriti-os]

+1, this should not be part of SDK and it adds unnecessary maintenance burden.

[cpriti-os]

Would be better to use helper function here and in http_client.go to keep UpdateObject method clean and modular?

[krishnamd-jkp]

The update logic is different for gRPC and HTTP. I think it's okay as it again follows other metadata fields