Use dependencies in vendor/ instead of downloading them

[amuttsch]

I have a Go project that uses modules and stores its dependencies in the vendor/ folder. In our CI pipeline, we install gomock and run it via //go:generate mockgen -source ./foo/service.go -destination gen/foo/mocks.go -package foo.

gomock then tries to download all dependencies from its source repositories instead of using the vendor folder. This is problematic for us as we have some dependencies in a private repo that uses self signed certificates. Thats why we want to use the vendor/ folder.

We execute go generate -mod vendor to trigger the generation, we tried prefixing it with GOFLAGS=-mod=vendor and using -build_flags "-mod vendor" , but gomock always downloads all dependencies.

How can we tell gomock to look for dependencies in the vendor folder first before downloading them? Thanks!

[soniah]

The standard suggestion is to use retool however retool isn't module aware 🤣 There's a blog post retooling retool about using mage to download build tool dependencies, I'm following up on that.

A possible solution to this issue/bug would to make mockgen it's own module, so it could be easily vendored using the go mod mechanisms.

[matyat]

I got this working by putting in my go:generate line -build_flags=-mod=vendor, no quotes. Must be something funny going on with how go generate escapes quotes maybe?

[soniah]

Thanks @Logibox. gomock is painful to use with modules, they've been going to fix it for a while, hopefully this is a working temporary fix.

[minicuts]

@Logibox I made a small fix #357 to address the -build_flags behavior.

@amuttsch has the workaround with -build_flags=-mod=vendor worked in your case? If yes I will consider to add automatic fallback to run module download mode vendor if default download mode fails.

@soniah It would be great if you provided some more details about issues you are running into with gomock and modules. I can try to think about how to improve that.

[codyoss]

@amuttsch @Logibox @soniah Any updates?

[soniah]

Hi @nguyenfilip @codyoss I haven't looked at this for ages, I'll have to think through the issues and implications. @nguyenfilip I can't remember the issues I was having.

I'm sure you've looked the HEAD of master; FYI mocks are now built into the mocks folder and the build command is described in the README. But this seems is a different issue.

@Logibox made the following comment earlier in the thread:

I got this working by putting in my go:generate line -build_flags=-mod=vendor, no quotes

What results did you get from this @codyoss ? I feel your pain about self signed certs. Have you tried setting up a go mod proxy using Athens?