cli: refactor to allow definition of subcommands next to their implementation

cli/cli.go

@@ -0,0 +1,105 @@
+package cli
+
+import (
+	"fmt"
+	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
+	"github.com/zrepl/zrepl/config"
+	"os"
+)
+
+var rootArgs struct {
+	configPath string
+}
+
+var rootCmd = &cobra.Command{
+	Use:   "zrepl",
+	Short: "One-stop ZFS replication solution",
+}
+
+var bashcompCmd = &cobra.Command{
+	Use:   "bashcomp path/to/out/file",
+	Short: "generate bash completions",
+	Run: func(cmd *cobra.Command, args []string) {
+		if len(args) != 1 {
+			fmt.Fprintf(os.Stderr, "specify exactly one positional agument\n")
+			cmd.Usage()
+			os.Exit(1)
+		}
+		if err := rootCmd.GenBashCompletionFile(args[0]); err != nil {
+			fmt.Fprintf(os.Stderr, "error generating bash completion: %s", err)
+			os.Exit(1)
+		}
+	},
+	Hidden: true,
+}
+
+func init() {
+	rootCmd.PersistentFlags().StringVar(&rootArgs.configPath, "config", "", "config file path")
+	rootCmd.AddCommand(bashcompCmd)
+}
+
+type Subcommand struct {
+	Use             string
+	Short           string
+	NoRequireConfig bool
+	Run             func(subcommand *Subcommand, args []string) error
+	SetupFlags      func(f *pflag.FlagSet)
+
+	config *config.Config
+	configErr error
+}
+
+func (s *Subcommand) ConfigParsingError() error {
+	return s.configErr
+}
+
+func (s *Subcommand) Config() *config.Config {
+	if !s.NoRequireConfig && s.config == nil {
+		panic("command that requires config is running and has no config set")
+	}
+	return s.config
+}
+
+func (s *Subcommand) run(cmd *cobra.Command, args []string) {
+	s.tryParseConfig()
+	err := s.Run(s, args)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n", err)
+		os.Exit(1)
+	}
+}
+
+func (s *Subcommand) tryParseConfig() {
+	config, err := config.ParseConfig(rootArgs.configPath)
+	s.configErr = err
+	if err != nil {
+		if s.NoRequireConfig {
+			// doesn't matter
+			return
+		} else {
+			fmt.Fprintf(os.Stderr, "could not parse config: %s\n", err)
+			os.Exit(1)
+		}
+	}
+	s.config = config
+}
+
+func AddSubcommand(s *Subcommand) {
+	cmd := cobra.Command{
+		Use: s.Use,
+		Short: s.Short,
+		Run: s.run,
+	}
+	if s.SetupFlags != nil {
+		s.SetupFlags(cmd.Flags())
+	}
+	rootCmd.AddCommand(&cmd)
+}
+
+
+func Run() {
+	if err := rootCmd.Execute(); err != nil {
+		os.Exit(1)
+	}
+}