must not already exist.

Init accepts one optional argument, the module path for the new module. If the
module path argument is omitted, init will attempt to infer the module path
using import comments in .go files, vendoring tool configuration files (like
Gopkg.lock), and the current directory (if in GOPATH).

See https://golang.org/ref/mod#go-mod-init for more about 'go mod init'.
`,
	Run: runInit,
}

func init() {

stdout rsc.io/sampler
! grep 'rsc.io/sampler v1.3.0' go.mod

# update to v1.3.1, now indirect in go.mod.
go get rsc.io/sampler@v1.3.1
grep 'rsc.io/sampler v1.3.1 // indirect' go.mod
cp go.mod go.mod.good

# vendoring can but should not need to make changes.
go mod vendor
cmp go.mod go.mod.good

# go list -mod=vendor (or go build -mod=vendor) must not modify go.mod.
# golang.org/issue/26704
go list -mod=vendor

# This test exercises that vendoring works properly using the workspace in the
# the work_prune test case.

go work vendor
cmp vendor/modules.txt modules.txt.want
cmp vendor/example.com/b/b.go b/b.go
cmp vendor/example.com/q/q.go q1_1_0/q.go
go list -m -f '{{.Version}}' example.com/q
stdout '^v1.1.0$'

go list -f '{{.Dir}}' example.com/q
stdout $GOPATH[\\/]src[\\/]vendor[\\/]example.com[\\/]q
go list -f '{{.Dir}}' example.com/b

env GO111MODULE=on

# Without vendoring, a build should succeed unless -mod=vendor is set.
[!short] go build
[!short] ! go build -mod=vendor

# Without vendoring, 'go list' should report the replacement directory for
# a package in a replaced module.
go list -f {{.Dir}} x
stdout 'src[\\/]x'

# 'go mod vendor' should copy all replaced modules to the vendor directory.
go mod vendor -v
stderr '^# x v1.0.0 => ./x'
stderr '^x'

// The prefixes are component-wise; for example, "golang.org/x"
// matches "golang.org/x/build" but not "golang.org/xyz".
//
// DO NOT ADD TO THIS LIST TO FIX BUILDS.
// Vendoring a new package requires prior discussion.
var allowedPackagePrefixes = []string{
	"golang.org/x",
	"github.com/google/pprof",
	"github.com/ianlancetaylor/demangle",
	"rsc.io/markdown",
}

Vendoring in std and cmd
========================

The Go command maintains copies of external packages needed by the
standard library in the src/vendor and src/cmd/vendor directories.

There are two modules, std and cmd, defined in src/go.mod and
src/cmd/go.mod. When a package outside std or cmd is imported
by a package inside std or cmd, the import path is interpreted
as if it had a "vendor/" prefix. For example, within "crypto/tls",

type moduleJSON struct {
	Path, Dir, GoVersion string
}

var modFlagRegexp = regexp.MustCompile(`-mod[ =](\w+)`)

// vendorEnabled indicates if vendoring is enabled.
// Inspired by setDefaultBuildMod in modload/init.go
func vendorEnabled() (*moduleJSON, bool, error) {
	mainMod, go114, err := getMainModuleAnd114()
	if err != nil {
		return nil, false, err
	}

# This test exercises that vendoring works properly using the workspace in the
# the work_prune test case.

go work vendor
cmp vendor/modules.txt modules.txt.want
go list -f '{{with .Module}}{{.Path}}@{{.Version}}{{end}}' all
cmp stdout want_versions

go list -f '{{.Dir}}' example.com/q
stdout $GOPATH[\\/]src[\\/]vendor[\\/]example.com[\\/]q
go list -f '{{.Dir}}' example.com/b
stdout $GOPATH[\\/]src[\\/]vendor[\\/]example.com[\\/]b

go list -mod=mod .
grep rsc.io/quote go.alt.mod
go build -n -mod=mod .
go test -n -mod=mod .
go get rsc.io/quote


# 'go mod vendor' should work.
go mod vendor
exists vendor

# Automatic vendoring should be broken by editing an explicit requirement
# in the alternate go.mod file.
go mod edit -require rsc.io/quote@v1.5.1
! go list .
go list -mod=mod
rm vendor

# 'go list -mod=vendor -retracted' reports an error.
go mod vendor
! go list -m -retracted -mod=vendor
stderr '^go list -retracted cannot be used when vendoring is enabled$'
rm vendor

# 'go list -retracted' reports an error in GOPATH mode.
env GO111MODULE=off
! go list -retracted
stderr '^go list -retracted can only be used in module-aware mode$'
env GO111MODULE=

# 'go list pkg' does not show retraction.