Integrate CLI plugins with docker help «foo»

Signed-off-by: Ian Campbell <ijc@docker.com>

cli-plugins/manager/manager.go

@@ -181,3 +181,10 @@ func PluginRunCommand(name string, rootcmd *cobra.Command) (*exec.Cmd, error) {
 	// they lack e.g. global options which we must propagate here.
 	return runPluginCommand(name, rootcmd, os.Args[1:])
 }
+
+// PluginHelpCommand returns an "os/exec".Cmd which when .Run() will execute the named plugin's help command.
+// The rootcmd argument is referenced to determine the set of builtin commands in order to detect conficts.
+// The error returned is an ErrPluginNotFound if no plugin was found or if the first candidate plugin was invalid somehow.
+func PluginHelpCommand(name string, rootcmd *cobra.Command) (*exec.Cmd, error) {
+	return runPluginCommand(name, rootcmd, []string{"help", name})
+}

cli/cobra.go

@@ -2,6 +2,7 @@ package cli
 
 import (
 	"fmt"
+	"os"
 	"strings"
 
 	pluginmanager "github.com/docker/cli/cli-plugins/manager"
@@ -57,6 +58,18 @@ var helpCommand = &cobra.Command{
 	RunE: func(c *cobra.Command, args []string) error {
 		cmd, args, e := c.Root().Find(args)
 		if cmd == nil || e != nil || len(args) > 0 {
+			if len(args) == 1 {
+				helpcmd, err := pluginmanager.PluginHelpCommand(args[0], cmd.Root())
+				if err == nil {
+					helpcmd.Stdin = os.Stdin
+					helpcmd.Stdout = os.Stdout
+					helpcmd.Stderr = os.Stderr
+					return helpcmd.Run()
+				}
+				if _, ok := err.(pluginmanager.ErrPluginNotFound); !ok {
+					return err
+				}
+			}
 			return errors.Errorf("unknown help topic: %v", strings.Join(args, " "))
 		}
 

e2e/cli-plugins/run_test.go

@@ -14,6 +14,20 @@ func TestRunNonexisting(t *testing.T) {
 	})
 }
 
+func TestHelpNonexisting(t *testing.T) {
+	res := icmd.RunCmd(icmd.Command("docker", "help", "nonexistent"))
+	res.Assert(t, icmd.Expected{
+		ExitCode: 1,
+		Err:      "unknown help topic: nonexistent",
+	})
+
+	res = icmd.RunCmd(icmd.Command("docker", "nonexistent", "--help"))
+	res.Assert(t, icmd.Expected{
+		ExitCode: 0,
+		Out: "Usage:	docker [OPTIONS] COMMAND",
+	})
+}
+
 func TestRunBad(t *testing.T) {
 	res := icmd.RunCmd(icmd.Command("docker", "badmeta"))
 	res.Assert(t, icmd.Expected{
@@ -22,10 +36,37 @@ func TestRunBad(t *testing.T) {
 	})
 }
 
+func TestHelpBad(t *testing.T) {
+	res := icmd.RunCmd(icmd.Command("docker", "help", "badmeta"))
+	res.Assert(t, icmd.Expected{
+		ExitCode: 1,
+		Err:      "unknown help topic: badmeta",
+	})
+
+	res = icmd.RunCmd(icmd.Command("docker", "badmeta", "--help"))
+	res.Assert(t, icmd.Expected{
+		ExitCode: 0,
+		Out: "Usage:	docker [OPTIONS] COMMAND",
+	})
+}
+
 func TestRunGood(t *testing.T) {
 	res := icmd.RunCmd(icmd.Command("docker", "helloworld"))
 	res.Assert(t, icmd.Expected{
 		ExitCode: 0,
 		Out:      "Hello World!",
 	})
 }
+
+func TestHelpGood(t *testing.T) {
+	res := icmd.RunCmd(icmd.Command("docker", "help", "helloworld"))
+	res.Assert(t, icmd.Expected{
+		ExitCode: 0,
+		Out:      "Usage:\n  docker helloworld",
+	})
+	res = icmd.RunCmd(icmd.Command("docker", "helloworld", "--help"))
+	res.Assert(t, icmd.Expected{
+		ExitCode: 0,
+		Out: "Usage:	docker helloworld",
+	})
+}