cmd/go: add go work use command

For #45713, #48257

Change-Id: I7e9248f22fe7ab33b151e07cc296d64c194154e2
Reviewed-on: https://go-review.googlesource.com/c/go/+/359534
Trust: Michael Matloob <matloob@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/cmd/go/alldocs.go

@@ -1388,6 +1388,7 @@
 // 	edit        edit go.work from tools or scripts
 // 	init        initialize workspace file
 // 	sync        sync workspace build list to modules
+// 	use         add modules to workspace file
 //
 // Use "go help work <command>" for more information about a command.
 //
@@ -1488,6 +1489,18 @@
 // go work sync
 //
 //
+// Add modules to workspace file
+//
+// Usage:
+//
+// 	go work use [-r] [moddirs]
+//
+// Use provides a command-line interface for adding directories,
+// optionally recursively, to a go.work file.
+//
+// The -r flag searches recursively for modules in the argument directories.
+//
+//
 // Compile and run Go program
 //
 // Usage:

src/cmd/go/internal/workcmd/use.go

@@ -0,0 +1,129 @@
+// 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 work use
+
+package workcmd
+
+import (
+	"cmd/go/internal/base"
+	"cmd/go/internal/fsys"
+	"cmd/go/internal/lockedfile"
+	"cmd/go/internal/modload"
+	"context"
+	"io/fs"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	"golang.org/x/mod/modfile"
+)
+
+var _ = modload.TODOWorkspaces("Add more documentation below. Though this is" +
+	"enough for those trying workspaces out, there should be more through" +
+	"documentation if the proposal is accepted and released.")
+
+var cmdUse = &base.Command{
+	UsageLine: "go work use [-r] [moddirs]",
+	Short:     "add modules to workspace file",
+	Long: `Use provides a command-line interface for adding directories,
+optionally recursively, to a go.work file.
+
+The -r flag searches recursively for modules in the argument directories.`,
+}
+
+var useR = cmdUse.Flag.Bool("r", false, "")
+
+func init() {
+	cmdUse.Run = runUse // break init cycle
+
+	base.AddModCommonFlags(&cmdUse.Flag)
+	base.AddWorkfileFlag(&cmdUse.Flag)
+}
+
+func runUse(ctx context.Context, cmd *base.Command, args []string) {
+	modload.InitWorkfile()
+
+	modload.ForceUseModules = true
+
+	var gowork string
+	modload.InitWorkfile()
+	gowork = modload.WorkFilePath()
+
+	data, err := lockedfile.Read(gowork)
+	if err != nil {
+		base.Fatalf("goX: %v", err)
+	}
+
+	workFile, err := modfile.ParseWork(gowork, data, nil)
+	if err != nil {
+		base.Fatalf("go: errors parsing %s:\n%s", base.ShortPath(gowork), err)
+	}
+
+	haveDirs := make(map[string]bool)
+	for _, dir := range workFile.Directory {
+		haveDirs[filepath.Join(filepath.Dir(gowork), filepath.FromSlash(dir.Path))] = true
+	}
+
+	addDirs := make(map[string]bool)
+	removeDirs := make(map[string]bool)
+	lookDir := func(dir string) {
+		absDir := filepath.Join(base.Cwd(), dir)
+		// If the path is absolute, keep it absolute. If it's relative,
+		// make it relative to the go.work file rather than the working directory.
+		if !filepath.IsAbs(dir) {
+			rel, err := filepath.Rel(filepath.Dir(gowork), absDir)
+			if err == nil {
+				dir = rel
+			}
+		}
+		fi, err := os.Stat(filepath.Join(dir, "go.mod"))
+		if err != nil {
+			if os.IsNotExist(err) {
+
+				if haveDirs[absDir] {
+					removeDirs[dir] = true
+				}
+				return
+			}
+			base.Errorf("go: %v", err)
+		}
+
+		if !fi.Mode().IsRegular() {
+			base.Errorf("go: %v is not regular", filepath.Join(dir, "go.mod"))
+		}
+
+		if !haveDirs[absDir] {
+			addDirs[dir] = true
+		}
+	}
+
+	for _, useDir := range args {
+		if *useR {
+			fsys.Walk(useDir, func(path string, info fs.FileInfo, err error) error {
+				if !info.IsDir() {
+					return nil
+				}
+				lookDir(path)
+				return nil
+			})
+			continue
+		}
+		lookDir(useDir)
+	}
+
+	for dir := range removeDirs {
+		workFile.DropDirectory(filepath.ToSlash(dir))
+	}
+	for dir := range addDirs {
+		workFile.AddDirectory(filepath.ToSlash(dir), "")
+	}
+	workFile.SortBlocks()
+	workFile.Cleanup() // clean file after edits
+	out := modfile.Format(workFile.Syntax)
+
+	if err := ioutil.WriteFile(gowork, out, 0666); err != nil {
+		base.Fatalf("go: %v", err)
+	}
+}

src/cmd/go/internal/workcmd/work.go

@@ -25,5 +25,6 @@ which workspaces are a part.
 		cmdEdit,
 		cmdInit,
 		cmdSync,
+		cmdUse,
 	},
 }

src/cmd/go/testdata/script/work_use.txt

@@ -0,0 +1,32 @@
+go work use -r foo
+cmp go.work go.want_work_r
+
+go work use other
+cmp go.work go.want_work_other
+-- go.work --
+go 1.18
+
+directory (
+	foo
+	foo/bar // doesn't exist
+)
+-- go.want_work_r --
+go 1.18
+
+directory (
+	foo
+	foo/bar/baz
+)
+-- go.want_work_other --
+go 1.18
+
+directory (
+	foo
+	foo/bar/baz
+	other
+)
+-- foo/go.mod --
+module foo
+-- foo/bar/baz/go.mod --
+module baz
+-- other/go.mod --