Generate shell completion scripts

cmd/completion.go

@@ -0,0 +1,36 @@
+package cmd
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/spf13/cobra"
+)
+
+const shellPowerShell = "powershell"
+
+func newCompletionCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:       "completion [bash|zsh|fish|powershell]",
+		Short:     "Generate shell completion scripts",
+		Args:      cobra.ExactArgs(1),
+		ValidArgs: []string{"bash", "zsh", "fish", shellPowerShell},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			out := cmd.OutOrStdout()
+			root := cmd.Root()
+
+			switch shell := strings.ToLower(args[0]); shell {
+			case "bash":
+				return root.GenBashCompletion(out)
+			case "zsh":
+				return root.GenZshCompletion(out)
+			case "fish":
+				return root.GenFishCompletion(out, true)
+			case shellPowerShell:
+				return root.GenPowerShellCompletion(out)
+			default:
+				return fmt.Errorf("unsupported shell %q (supported: bash, zsh, fish, %s)", args[0], shellPowerShell)
+			}
+		},
+	}
+}

cmd/completion_test.go

@@ -0,0 +1,48 @@
+package cmd
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/spf13/cobra"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCompletionCmd_GeneratesPowerShell(t *testing.T) {
+	root := &cobra.Command{Use: "app"}
+	root.AddCommand(newCompletionCmd())
+
+	var out bytes.Buffer
+	root.SetOut(&out)
+	root.SetErr(&out)
+	root.SetArgs([]string{"completion", "powershell"})
+
+	err := root.Execute()
+
+	require.NoError(t, err)
+	assert.Contains(t, out.String(), "Register-ArgumentCompleter")
+}
+
+func TestCompletionCmd_RejectsUnsupportedShell(t *testing.T) {
+	root := &cobra.Command{Use: "app"}
+	root.AddCommand(newCompletionCmd())
+
+	root.SetArgs([]string{"completion", "xonsh"})
+
+	err := root.Execute()
+
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "unsupported shell")
+}
+
+func TestRootRegistersCompletionCommand(t *testing.T) {
+	root, cleanup := newRootCommand()
+	defer cleanup()
+
+	completionCmd, _, err := root.Find([]string{"completion"})
+
+	require.NoError(t, err)
+	require.NotNil(t, completionCmd)
+	assert.Equal(t, "completion", completionCmd.Name())
+}

cmd/root.go

@@ -357,6 +357,7 @@ Environment:
 	rootCmd.AddCommand(newRunCmd())
 	rootCmd.AddCommand(newReportCmd())
 	rootCmd.AddCommand(newConfigCmd())
+	rootCmd.AddCommand(newCompletionCmd())
 
 	// cleanup releases profiling resources. It is idempotent — safe to call
 	// multiple times (subsequent calls are no-ops).

docs/completions.md

@@ -0,0 +1,12 @@
+# Shell completions
+
+Generate a completion script for your shell:
+
+```bash
+grut completion bash
+grut completion zsh
+grut completion fish
+grut completion powershell
+```
+
+Write the generated script to the location your shell expects, then reload the shell.