add containedctx linter

[sivchari]

containedctx is a linter that detects struct contained context.Context field
in detail, please check following link.
https://github.com/sivchari/containedctx

[Antonboom]

@sivchari, FYI – it's OK pass Context in the struct for tracing purpose.

For example:

result := client.ExternalServiceCall()
span, ctx := tracer.ExtractSpan(result.Ctx)
// Deal with external service span.

[sivchari]

context

Do not store Contexts inside a struct type; instead, pass a Context explicitly to each function that needs it. The Context should be the first parameter, typically named ctx

Your example code depends on package design of 3rd library.
And, this linter don't detect external code.
Additional, if you wanna to contain context.Context in struct, you can disable this linter.

[Antonboom]

@sivchari I'm familiar with context doc :)
Yes, you can blame the third-party library, but it's hard to argue with it when it is the de facto standard.

I have nothing against the linter. It was just notification for u, that not everything is so simple.

[sivchari]

I'm not sure which library you mean by de facto standard, but Many third-library declared interface to pass context to first parameter.
The third-library for using data tracing (e.g. dogstatsd, prometheus API ) shod be pass the first parameter too.
However, it's also true, as you say, that some third libraries contain context.Context in struct.
But Go team recommends not to contain context.Context in struct, so this linter is meant to keep it that way.
Thanks for comment.

[sivchari]

Back to the linter. I'm improving that.
Because, in the current function, the linter detects test case (e.g. table-driven-test).
table-driven-test is general and context is sometime contained in struct too.
So I'm improving to exclude test file.

[bombsimon]

Back to the linter. I'm improving that. Because, in the current function, the linter detects test case (e.g. table-driven-test). table-driven-test is general and context is sometime contained in struct too. So I'm improving to exclude test file.

You don't have to do that in your linter for golangci-lint though, generally skipping tests in golangci-lint is handled with the implementation of that feature in golangci-lint itself. I'm also not sure skipping whole test files is the right way to go, I can see use cases of wanting to use this linter on test files as well.

[sivchari]

You don't have to do that in your linter for golangci-lint though, generally skipping tests in golangci-lint is handled with the implementation of that feature in golangci-lint itself. I'm also not sure skipping whole test files is the right way to go, I can see use cases of wanting to use this linter on test files as well.

Oh, I've mistook.
Thanks !

[ldez]

LGTM