Install gvt

After doing some research, I decided to try gvt since it seemed simple and well documented, and integrated well with exiting tools like go get.

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$ export GO15VENDOREXPERIMENT=1
$ go get -u github.com/FiloSottile/gvt

Go get target project to be updated

I’m going to update todolite-appserver to use vendored dependencies for some of it’s dependencies, just to see how things go.

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$ go get -u github.com/tleyden/todolite-appserver

Vendor dependencies

I’m going to vendor the dependency on kingpin since it has transitive dependencies of it’s own (github.com/alecthomas/units, etc). gvt handles this by automatically pulling all of the transitive dependencies.

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$ gvt fetch github.com/alecthomas/kingpin

Now my directory structure looks like this:

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├── main.go
└── vendor
    ├── github.com
    │   └── alecthomas
    ├── gopkg.in
    │   └── alecthomas
    └── manifest

Here is the manifest

gvt list shows the following:

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$  gvt list
github.com/alecthomas/kingpin  https://github.com/alecthomas/kingpin  master 46aba6af542541c54c5b7a71a9dfe8f2ab95b93a
github.com/alecthomas/template https://github.com/alecthomas/template master 14fd436dd20c3cc65242a9f396b61bfc8a3926fc
github.com/alecthomas/units    https://github.com/alecthomas/units    master 2efee857e7cfd4f3d0138cc3cbb1b4966962b93a
gopkg.in/alecthomas/kingpin.v2 https://gopkg.in/alecthomas/kingpin.v2 master 24b74030480f0aa98802b51ff4622a7eb09dfddd

Verify it’s using the vendor folder

I opened up the vendor/github.com/alecthomas/kingpin/global.go and made the following change:

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// Errorf prints an error message to stderr.
func Errorf(format string, args ...interface{}) {
  fmt.Println("CALLED IT!!")
  CommandLine.Errorf(format, args...)
}

Now verify that code is getting compiled and run:

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$ go run main.go changesfollower
CALLED IT!!
main: error: URL is empty

(note: export GO15VENDOREXPERIMENT=1 is still in effect in my shell)

Restore the dependency

Before I check in the vendor directory to git, I want to reset it to it’s previous state before I made the above change to the global.go source file.

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$ gvt restore

Now if I open global.go again, it’s back to it’s original state. Nice!

Add the vendor folder and push

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$ git add vendor
$ git commit -m "..."
$ git push origin master

Also, I updated the README to tell users to set the GO15VENDOREXPERIMENT=1 variable:

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$ export GO15VENDOREXPERIMENT=1
$ go get -u github.com/tleyden/todolite-appserver
$ todolite-appserver --help

but the instructions otherwise remained the same. If someone tries to use this but forgets to set GO15VENDOREXPERIMENT=1 in Go 1.5, it will still work, it will just use the kingpin dependency in the $GOPATH rather than the vendor/ directory. Ditto for someone using go 1.4 or earlier.

Removing a vendored dependency

As it turns out, I don’t even need kingpin in this project, since I’m using cobra. The kingpin dependency was caused by some leftover code I forgot to cleanup.

To remove it, I ran:

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$ gvt delete github.com/alecthomas/kingpin
$ gvt delete github.com/alecthomas/template
$ gvt delete github.com/alecthomas/units
$ gvt delete gopkg.in/alecthomas/kingpin.v2

In this case, since it was my only dependency, it was easy to identify the transitive dependencies. In general though it looks like it’s up to you as a user to track down which ones to remove. I filed gvt issue 16 to hopefully address that.

Editor annoyances

I have emacs setup using the steps in this blog post, and I’m running into the following annoyances:

• When I use godef to jump into the code of vendored dependency, it takes me to source code that lives in the GOPATH, which might be different than what’s under vendor/. Also, if I edit it there, my changes won’t be reflected when I rebuild.
• I usually search for things in the project via M-x rgrep, but now it’s searching through every repo under vendor/ and returning things I’m not interested in .. since most of the time I only want to search within my project.