Failure all dirs lacked any go code when pre-loading vendor/ directory with dep ensure in Docker Build

[maxmeyer]

What version of Go (go version) and dep (git describe --tags) are you using?

Go: 1.8.3
Dep: v0.2.1-6-gc1aba4d

What dep command did you run?

I would like to use dep inside a build container. I also have vendor/ set up by dep in the project root and there's also no entry in the .dockerignore-file preventing the directory to be passed to the "Docker"-daemon. Those are the example Dockerfiles for the build environment.

1. Naive approach

   FROM golang:1.8-alpine
   
   RUN go get -u github.com/golang/dep/cmd/dep
   
   WORKDIR /go/src/github.com/example/project
   
   COPY . .
   
   RUN dep ensure
   RUN make
   

   The problem here is, that dep ensure is needed to run every time, when there are code changes to . which takes around 10 mins. Even using a caching HTTP proxy will only help to reduce that costs for the infrastructure where the proxy is enrolled.

2. Better approach - which fails

   FROM golang:1.8-alpine
   
   RUN go get -u github.com/golang/dep/cmd/dep
   
   WORKDIR /go/src/github.com/example/project
   
   COPY Gopkg.* ./
   RUN dep ensure
   
   COPY . .  
   RUN dep ensure
   
   RUN make
   

   This fails with all dirs lacked any go code. You see this kind of pattern in Ruby-applications to speed up the docker build. This makes use of "Docker"'s inbuild caching mechanism. Adding a more or less empty main.go does not help either.

What did you expect to see?

Install packages without any error

What did you see instead?

all dirs lacked any go code

[sdboyer]

hi! i believe that #796 describes exactly what you're looking for, and - as of Friday's merge - you can achieve this with dep ensure -vendor-only 😄

[maxmeyer]

Sounds great! What about deb ensure -local to prevent any network communication?

[sdboyer]

that'd be what something like #945 is about 😄