1 files changed, 82 insertions, 0 deletions
diff --git a/src/cmd/go/internal/modcmd/graph.go b/src/cmd/go/internal/modcmd/graph.go
new file mode 100644
index 0000000..555604d
--- /dev/null
+++ b/src/cmd/go/internal/modcmd/graph.go
@@ -0,0 +1,82 @@
+// Copyright 2018 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 graph
+
+package modcmd
+
+import (
+	"bufio"
+	"context"
+	"os"
+
+	"cmd/go/internal/base"
+	"cmd/go/internal/cfg"
+	"cmd/go/internal/modload"
+
+	"golang.org/x/mod/module"
+)
+
+var cmdGraph = &base.Command{
+	UsageLine: "go mod graph [-go=version] [-x]",
+	Short:     "print module requirement graph",
+	Long: `
+Graph prints the module requirement graph (with replacements applied)
+in text form. Each line in the output has two space-separated fields: a module
+and one of its requirements. Each module is identified as a string of the form
+path@version, except for the main module, which has no @version suffix.
+
+The -go flag causes graph to report the module graph as loaded by the
+given Go version, instead of the version indicated by the 'go' directive
+in the go.mod file.
+
+The -x flag causes graph to print the commands graph executes.
+
+See https://golang.org/ref/mod#go-mod-graph for more about 'go mod graph'.
+	`,
+	Run: runGraph,
+}
+
+var (
+	graphGo goVersionFlag
+)
+
+func init() {
+	cmdGraph.Flag.Var(&graphGo, "go", "")
+	cmdGraph.Flag.BoolVar(&cfg.BuildX, "x", false, "")
+	base.AddChdirFlag(&cmdGraph.Flag)
+	base.AddModCommonFlags(&cmdGraph.Flag)
+}
+
+func runGraph(ctx context.Context, cmd *base.Command, args []string) {
+	modload.InitWorkfile()
+
+	if len(args) > 0 {
+		base.Fatalf("go: 'go mod graph' accepts no arguments")
+	}
+	modload.ForceUseModules = true
+	modload.RootMode = modload.NeedRoot
+	mg := modload.LoadModGraph(ctx, graphGo.String())
+
+	w := bufio.NewWriter(os.Stdout)
+	defer w.Flush()
+
+	format := func(m module.Version) {
+		w.WriteString(m.Path)
+		if m.Version != "" {
+			w.WriteString("@")
+			w.WriteString(m.Version)
+		}
+	}
+
+	mg.WalkBreadthFirst(func(m module.Version) {
+		reqs, _ := mg.RequiredBy(m)
+		for _, r := range reqs {
+			format(m)
+			w.WriteByte(' ')
+			format(r)
+			w.WriteByte('\n')
+		}
+	})
+}