feat(cli): add shell completions (#14341)

cli/completion.go

@@ -0,0 +1,89 @@
+package cli
+
+import (
+	"fmt"
+
+	"github.com/coder/coder/v2/cli/cliui"
+	"github.com/coder/serpent"
+	"github.com/coder/serpent/completion"
+)
+
+func (*RootCmd) completion() *serpent.Command {
+	var shellName string
+	var printOutput bool
+	shellOptions := completion.ShellOptions(&shellName)
+	return &serpent.Command{
+		Use:   "completion",
+		Short: "Install or update shell completion scripts for the detected or chosen shell.",
+		Options: []serpent.Option{
+			{
+				Flag:          "shell",
+				FlagShorthand: "s",
+				Description:   "The shell to install completion for.",
+				Value:         shellOptions,
+			},
+			{
+				Flag:          "print",
+				Description:   "Print the completion script instead of installing it.",
+				FlagShorthand: "p",
+
+				Value: serpent.BoolOf(&printOutput),
+			},
+		},
+		Handler: func(inv *serpent.Invocation) error {
+			if shellName != "" {
+				shell, err := completion.ShellByName(shellName, inv.Command.Parent.Name())
+				if err != nil {
+					return err
+				}
+				if printOutput {
+					return shell.WriteCompletion(inv.Stdout)
+				}
+				return installCompletion(inv, shell)
+			}
+			shell, err := completion.DetectUserShell(inv.Command.Parent.Name())
+			if err == nil {
+				return installCompletion(inv, shell)
+			}
+			// Silently continue to the shell selection if detecting failed.
+			choice, err := cliui.Select(inv, cliui.SelectOptions{
+				Message: "Select a shell to install completion for:",
+				Options: shellOptions.Choices,
+			})
+			if err != nil {
+				return err
+			}
+			shellChoice, err := completion.ShellByName(choice, inv.Command.Parent.Name())
+			if err != nil {
+				return err
+			}
+			if printOutput {
+				return shellChoice.WriteCompletion(inv.Stdout)
+			}
+			return installCompletion(inv, shellChoice)
+		},
+	}
+}
+
+func installCompletion(inv *serpent.Invocation, shell completion.Shell) error {
+	path, err := shell.InstallPath()
+	if err != nil {
+		cliui.Error(inv.Stderr, fmt.Sprintf("Failed to determine completion path %v", err))
+		return shell.WriteCompletion(inv.Stdout)
+	}
+	choice, err := cliui.Select(inv, cliui.SelectOptions{
+		Options: []string{
+			"Confirm",
+			"Print to terminal",
+		},
+		Message:    fmt.Sprintf("Install completion for %s at %s?", shell.Name(), path),
+		HideSearch: true,
+	})
+	if err != nil {
+		return err
+	}
+	if choice == "Print to terminal" {
+		return shell.WriteCompletion(inv.Stdout)
+	}
+	return completion.InstallShellCompletion(shell)
+}