flags: factor AddFlagsFromOptions from cmd

This is in preparation for generalising the backend config

cmd/cmd.go

@@ -522,41 +522,12 @@ var backendFlags map[string]struct{}
 func AddBackendFlags() {
 	backendFlags = map[string]struct{}{}
 	for _, fsInfo := range fs.Registry {
-		done := map[string]struct{}{}
+		flags.AddFlagsFromOptions(pflag.CommandLine, fsInfo.Prefix, fsInfo.Options)
+		// Store the backend flag names for the help generator
 		for i := range fsInfo.Options {
 			opt := &fsInfo.Options[i]
-			// Skip if done already (e.g. with Provider options)
-			if _, doneAlready := done[opt.Name]; doneAlready {
-				continue
-			}
-			done[opt.Name] = struct{}{}
-			// Make a flag from each option
 			name := opt.FlagName(fsInfo.Prefix)
-			found := pflag.CommandLine.Lookup(name) != nil
+			backendFlags[name] = struct{}{}
-			if !found {
-				// Take first line of help only
-				help := strings.TrimSpace(opt.Help)
-				if nl := strings.IndexRune(help, '\n'); nl >= 0 {
-					help = help[:nl]
-				}
-				help = strings.TrimRight(strings.TrimSpace(help), ".!?")
-				if opt.IsPassword {
-					help += " (obscured)"
-				}
-				flag := pflag.CommandLine.VarPF(opt, name, opt.ShortOpt, help)
-				flags.SetDefaultFromEnv(pflag.CommandLine, name)
-				if _, isBool := opt.Default.(bool); isBool {
-					flag.NoOptDefVal = "true"
-				}
-				// Hide on the command line if requested
-				if opt.Hide&fs.OptionHideCommandLine != 0 {
-					flag.Hidden = true
-				}
-				backendFlags[name] = struct{}{}
-			} else {
-				fs.Errorf(nil, "Not adding duplicate flag --%s", name)
-			}
-			// flag.Hidden = true
 		}
 	}
 }

fs/config/flags/flags.go

@@ -151,7 +151,7 @@ func installFlag(flags *pflag.FlagSet, name string, groupsString string) {
 	}
 
 	// Add flag to Group if it is a global flag
-	if flags == pflag.CommandLine {
+	if groupsString != "" && flags == pflag.CommandLine {
 		for _, groupName := range strings.Split(groupsString, ",") {
 			if groupName == "rc-" {
 				groupName = "RC"
@@ -165,24 +165,6 @@ func installFlag(flags *pflag.FlagSet, name string, groupsString string) {
 	}
 }
 
-// SetDefaultFromEnv constructs a name from the flag passed in and
-// sets the default from the environment if possible
-//
-// Used to create backend flags like --skip-links
-func SetDefaultFromEnv(flags *pflag.FlagSet, name string) {
-	envKey := fs.OptionToEnv(name)
-	envValue, found := os.LookupEnv(envKey)
-	if found {
-		flag := flags.Lookup(name)
-		if flag == nil {
-			log.Fatalf("Couldn't find flag --%q", name)
-		}
-		fs.Debugf(nil, "Setting default for %s=%q from environment variable %s", name, envValue, envKey)
-		//err = tempValue.Set()
-		flag.DefValue = envValue
-	}
-}
-
 // StringP defines a flag which can be set by an environment variable
 //
 // It is a thin wrapper around pflag.StringP
@@ -350,3 +332,45 @@ func CountVarP(flags *pflag.FlagSet, p *int, name, shorthand string, usage strin
 	flags.CountVarP(p, name, shorthand, usage)
 	installFlag(flags, name, groups)
 }
+
+// AddFlagsFromOptions takes a slice of fs.Option and adds flags for all of them
+func AddFlagsFromOptions(flags *pflag.FlagSet, prefix string, options fs.Options) {
+	done := map[string]struct{}{}
+	for i := range options {
+		opt := &options[i]
+		// Skip if done already (e.g. with Provider options)
+		if _, doneAlready := done[opt.Name]; doneAlready {
+			continue
+		}
+		done[opt.Name] = struct{}{}
+		// Make a flag from each option
+		if prefix == "" {
+			opt.NoPrefix = true
+		}
+		name := opt.FlagName(prefix)
+		found := flags.Lookup(name) != nil
+		if !found {
+			// Take first line of help only
+			help := strings.TrimSpace(opt.Help)
+			if nl := strings.IndexRune(help, '\n'); nl >= 0 {
+				help = help[:nl]
+			}
+			help = strings.TrimRight(strings.TrimSpace(help), ".!?")
+			if opt.IsPassword {
+				help += " (obscured)"
+			}
+			flag := flags.VarPF(opt, name, opt.ShortOpt, help)
+			installFlag(flags, name, opt.Groups)
+			if _, isBool := opt.Default.(bool); isBool {
+				flag.NoOptDefVal = "true"
+			}
+			// Hide on the command line if requested
+			if opt.Hide&fs.OptionHideCommandLine != 0 {
+				flag.Hidden = true
+			}
+		} else {
+			fs.Errorf(nil, "Not adding duplicate flag --%s", name)
+		}
+		// flag.Hidden = true
+	}
+}