x/build/gerrit: support Contexts?

[kevinburke]

If you are making concurrent requests with the Gerrit API client in x/build/gerrit, it would be nice to be able to coordinate cancelation if the request is no longer necessary.

For example, https://go-review.googlesource.com/#/c/35551/ would fetch Github issues and Gerrit CL's in parallel; it would be nice to cancel one if the other fails.

There's some preliminary discussion about migrating a client library here, on the go-github project: google/go-github#526

Some options, none of which I am very happy about:

• Change the API.
• Adding XContext(ctx, args...) methods on the existing Client for every X method, e.g. AbandonChangeContext, CreateProjectContext, etc.
• Add a ContextClient that has a Context property on the Client struct, and give up on reusing that client across requests.
• Add a ContextClient that has the same methods, but with a Context parameter as the first argument, so you'd choose which client you want based on whether you want contexts or not.
• Copy to x/build/gerrit2, x/build/gerritctx or similar with a renamed set of API's.
• Do nothing.

[dmitshur]

Copy to x/build/gerrit2, x/build/gerritctx or similar with a renamed set of API's.

In theory, with some amount of work, such a package can be automatically generated by source code rewriting of the original package. Then it can be easily kept in sync, it'd be just go generate. But I think it's a bad idea to have 2 packages permanently, if there's no long term plan to eventually join them (which would require breaking APIs).

[bradfitz]

The real bug is #18743

Then we can simply add contexts. We're not going to maintain double the API surface. We can barely maintain 1x the API surface.

[bradfitz]

@kevinburke, feel free to add contexts.

[gopherbot]

CL https://golang.org/cl/35559 mentions this issue.