Ensure without go code

[ebati]

What does this do / why do we need it?

dep ensure -vendor-only can now work in folder without any go code. It is especially useful for builds inside docker utilizing cache layers.

Sample dockerfile:

FROM golang:1.8 AS builder

RUN apt-get update && apt-get install -y unzip --no-install-recommends && \
    apt-get autoremove -y && apt-get clean -y && \
    wget -O dep.zip https://github.com/golang/dep/releases/download/v0.3.0/dep-linux-amd64.zip && \
    echo '96c191251164b1404332793fb7d1e5d8de2641706b128bf8d65772363758f364  dep.zip' | sha256sum -c - && \
    unzip -d /usr/bin dep.zip && rm dep.zip

RUN mkdir -p /go/src/github.com/***
WORKDIR /go/src/github.com/***

COPY Gopkg.toml Gopkg.lock ./

RUN dep ensure -vendor-only
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -ldflags "-s -w" -a -installsuffix cgo -o *** 

FROM alpine:latest
RUN apk --no-cache add ca-certificates

WORKDIR /root/

COPY --from=builder /go/src/github.com/***  .
ENTRYPOINT ["./***"]

What should your reviewer look out for in this PR?

• runVendorOnly splitted from runDefault and called before ListPackages in ensure.Run
• harness_test nocode_vendoronly added by duplicating hashnew_vendoronly and removing main.go

Which issue(s) does this PR fix?

fixes #796

[sdboyer]

yep! easy peasy. and good call, moving it up above the ListPackages() call.

[sdboyer]

yaaaay first PR! 🎉 🎊

[netrounds-joakim]

FROM golang:1.8 AS builder

# Install dep
RUN apt-get update && apt-get install -y unzip --no-install-recommends && \
    apt-get autoremove -y && apt-get clean -y && \
    wget -O dep.zip https://github.com/golang/dep/releases/download/v0.3.0/dep-linux-amd64.zip && \
    echo '96c191251164b1404332793fb7d1e5d8de2641706b128bf8d65772363758f364  dep.zip' | sha256sum -c - && \
    unzip -d /usr/bin dep.zip && rm dep.zip

RUN mkdir -p /go/src/github.com/***
WORKDIR /go/src/github.com/***

COPY Gopkg.toml Gopkg.lock ./

RUN dep ensure -vendor-only
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -ldflags "-s -w" -a -installsuffix cgo -o *** 

FROM alpine:latest
RUN apk --no-cache add ca-certificates

WORKDIR /root/

COPY --from=builder /go/src/github.com/***  .
ENTRYPOINT ["./***"]

I used the exact Dockerfile as in this PR but I get this when building docker build -t ta2 .:

...
Archive:  dep.zip
  inflating: /usr/bin/dep
 ---> c682f0f63ba5
Removing intermediate container ec673c1eb0c4
Step 3/13 : RUN mkdir -p /go/src/github.com/***
 ---> Running in eac2e56b6b27
 ---> 647eac1a464b
Removing intermediate container eac2e56b6b27
Step 4/13 : WORKDIR /go/src/github.com/***
 ---> f9b96d48f844
Removing intermediate container ef017da7a94b
Step 5/13 : COPY Gopkg.toml Gopkg.lock ./
 ---> 85acdf026334
Removing intermediate container 1789b9f53060
Step 6/13 : RUN dep ensure -vendor-only
 ---> Running in 6ef8974e7302
all dirs lacked any go code
The command '/bin/sh -c dep ensure -vendor-only' returned a non-zero code: 1

I actually have a go file in this dir. main.go:

package main

import "fmt"

func main() {
	fmt.Println("hello world")
}

However my Gopkg.lock and Gopkg.toml are completely empty (maybe that is the issue?).