[dev.cmdgo] cmd/go: add go mod initwork command

This command is used to create a go.work file with a set of modules
given in the arguments to the command.

For #45713
Change-Id: I09f8cefc5849dd43c234dc4a37091791fcc02ebe
Reviewed-on: https://go-review.googlesource.com/c/go/+/334936
Trust: Michael Matloob <matloob@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

2 files changed, 55 insertions, 0 deletions

diff --git a/src/cmd/go/internal/modcmd/initwork.go b/src/cmd/go/internal/modcmd/initwork.go
new file mode 100644
index 0000000000..30653503bc
--- /dev/null
+++ b/src/cmd/go/internal/modcmd/initwork.go
@@ -0,0 +1,54 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// go mod initwork
+
+package modcmd
+
+import (
+	"cmd/go/internal/base"
+	"cmd/go/internal/modload"
+	"context"
+	"path/filepath"
+)
+
+var _ = modload.TODOWorkspaces("Add more documentation below.T hough this is" +
+	"enough for those trying workspaces out, there should be more through" +
+	"documentation if the proposal is accepted.")
+
+var cmdInitwork = &base.Command{
+	UsageLine: "go mod initwork [moddirs]",
+	Short:     "initialize workspace file",
+	Long: `go mod initwork initializes and writes a new go.work file in the current
+directory, in effect creating a new workspace at the current directory.
+
+go mod initwork optionally accepts paths to the workspace modules as arguments.
+If the argument is omitted, an empty workspace with no modules will be created.
+
+See the workspaces design proposal at
+https://go.googlesource.com/proposal/+/master/design/45713-workspace.md for
+more information.
+`,
+	Run: runInitwork,
+}
+
+func init() {
+	base.AddModCommonFlags(&cmdInitwork.Flag)
+	base.AddWorkfileFlag(&cmdInitwork.Flag)
+}
+
+func runInitwork(ctx context.Context, cmd *base.Command, args []string) {
+	modload.InitWorkfile()
+
+	modload.ForceUseModules = true
+
+	// TODO(matloob): support using the -workfile path
+	// To do that properly, we'll have to make the module directories
+	// make dirs relative to workFile path before adding the paths to
+	// the directory entries
+
+	workFile := filepath.Join(base.Cwd(), "go.work")
+
+	modload.CreateWorkFile(ctx, workFile, args)
+}
diff --git a/src/cmd/go/internal/modcmd/mod.go b/src/cmd/go/internal/modcmd/mod.go
index d72d0cacd6..3586b44c1a 100644
--- a/src/cmd/go/internal/modcmd/mod.go
+++ b/src/cmd/go/internal/modcmd/mod.go
@@ -25,6 +25,7 @@ See 'go help modules' for an overview of module functionality.
 		cmdEdit,
 		cmdGraph,
 		cmdInit,
+		cmdInitwork,
 		cmdTidy,
 		cmdVendor,
 		cmdVerify,