Godep

Command godep helps build packages reproducibly by fixing their dependencies.

This tool assumes you are working in a standard Go workspace, as described in http://golang.org/doc/code.html. We require Go 1.1 or newer to build godep itself, but you can use it on any project that works with Go 1 or newer.

Install

$ go get github.com/tools/godep

Getting Started

How to add godep in a new project.

Assuming you've got everything working already, so you can build your project with go install and test it with go test, it's one command to start using:

$ godep save

This will save a list of dependencies to the file Godeps/Godeps.json, and copy their source code into Godeps/_workspace. Read over its contents and make sure it looks reasonable. Then commit the whole Godeps directory to version control, including _workspace.

An additional flag -r can optionally be applied to the save command in order to automatically rewrite package import paths. Using godep save -r will rewrite all package import paths so that they refer directly to the copied source code in Godeps/_workspace. So, a package C that depends on package D will actually import C/Godeps/_workspace/src/D. This makes C's repo self-contained and causes 'go get' to build C with the right version of all dependencies.

Restore

The godep restore command is the opposite of godep save. It will install the package versions specified in Godeps/Godeps.json to your GOPATH.

Edit-test Cycle

1. Edit code
2. Run godep go test
3. (repeat)

Add a Dependency

To add a new package foo/bar, do this:

1. Run go get foo/bar
2. Edit your code to import foo/bar.
3. Run godep save (or godep save ./...).

Update a Dependency

To update a package from your $GOPATH, do this:

1. Run go get -u foo/bar
2. Run godep update foo/bar. (You can use the ... wildcard, for example godep update foo/...).

Before committing the change, you'll probably want to inspect the changes to Godeps, for example with git diff, and make sure it looks reasonable.

Multiple Packages

If your repository has more than one package, you're probably accustomed to running commands like go test ./..., go install ./..., and go fmt ./.... Similarly, you should run godep save ./... to capture the dependencies of all packages.

Using Other Tools

The godep path command helps integrate with commands other than the standard go tool. This works with any tool that reads GOPATH from its environment, for example the recently-released oracle command.

$ GOPATH=`godep path`:$GOPATH
$ oracle -mode=implements .

Old Format

Old versions of godep wrote the dependency list to a file Godeps, and didn't copy source code. This mode no longer exists, but commands 'godep go' and 'godep path' will continue to read the old format for some time.

File Format

Godeps is a json file with the following structure:

type Godeps struct {
	ImportPath string
	GoVersion  string   // Abridged output of 'go version'.
	Packages   []string // Arguments to godep save, if any.
	Deps       []struct {
		ImportPath string
		Comment    string // Description of commit, if present.
		Rev        string // VCS-specific commit ID.
	}
}

Example Godeps:

{
	"ImportPath": "github.com/kr/hk",
	"GoVersion": "go1.1.2",
	"Deps": [
		{
			"ImportPath": "code.google.com/p/go-netrc/netrc",
			"Rev": "28676070ab99"
		},
		{
			"ImportPath": "github.com/kr/binarydist",
			"Rev": "3380ade90f8b0dfa3e363fd7d7e941fa857d0d13"
		}
	]
}

Go 1.5 vendor/ experiment

Godep has preliminary support for the Go 1.5 vendor/ experiment utilizing the same environment variable that the go tooling itself supports: export GO15VENDOREXPERIMENT=1

When GO15VENDOREXPERIMENT=1 godep will write the vendored code into the local package's vendor directory. A Godeps/Godeps.json file is created, just like during normal operation. The vendor experiment is not compatible with rewrites.

There is currently no automated migration between the old Godeps workspace and the vendor directory, but the following steps should work:

$ unset GO15VENDOREXPERIMENT
$ godep restore
# The next line is only needed to automatically undo rewritten imports that were
# created with godep save -r.
$ godep save ./...
$ rm -rf Godeps
$ export GO15VENDOREXPERIMENT=1
$ godep save ./...
$ git add -A
# You should see your Godeps/_workspace/src files "moved" to vendor/.

NOTE: There is a "bug" in the vendor experiment that makes using ./... with the go tool (like go install) consider all packages inside the vendor directory: golang/go#11659. As a workaround you can do:

$ go <cmd> $(go list ./... | grep -v /vendor/)