commands: Check argument validity when running commands

commands/command.go

@@ -19,6 +19,12 @@ type Function func(Response, Request)
 // MAYBE_TODO: maybe this should be a io.Reader instead of a string?
 type Formatter func(Response) (string, error)
 
+// TODO: check Argument definitions when creating a Command
+//   (might need to use a Command constructor)
+//   * make sure any variadic args are at the end
+//   * make sure there aren't duplicate names
+//   * make sure optional arguments aren't followed by required arguments
+
 // Command is a runnable command, with input arguments and options (flags).
 // It can also have Subcommands, to group units of work into sets.
 type Command struct {
@@ -52,6 +58,12 @@ func (c *Command) Call(req Request) Response {
 		return res
 	}
 
+	err = req.CheckArguments(cmd.Arguments)
+	if err != nil {
+		res.SetError(err, ErrClient)
+		return res
+	}
+
 	options, err := c.GetOptions(req.Path())
 	if err != nil {
 		res.SetError(err, ErrClient)

commands/request.go

@@ -2,6 +2,7 @@ package commands
 
 import (
 	"fmt"
+	"io"
 	"reflect"
 	"strconv"
 
@@ -28,6 +29,7 @@ type Request interface {
 	SetContext(Context)
 	Command() *Command
 
+	CheckArguments(args []Argument) error
 	ConvertOptions(options map[string]Option) error
 }
 
@@ -101,6 +103,36 @@ var converters = map[reflect.Kind]converter{
 	},
 }
 
+// MAYBE_TODO: maybe this should be a Command method? (taking a Request as a param)
+func (r *request) CheckArguments(args []Argument) error {
+	var argDef Argument
+
+	for i, arg := range r.arguments {
+		if i < len(args) {
+			argDef = args[i]
+		} else if !argDef.Variadic {
+			return fmt.Errorf("Expected %v arguments, got %v", len(args), len(r.arguments))
+		}
+
+		if argDef.Required && arg == nil {
+			return fmt.Errorf("Argument '%s' is required", argDef.Name)
+		}
+		if argDef.Type == ArgFile {
+			_, ok := arg.(io.Reader)
+			if !ok {
+				return fmt.Errorf("Argument '%s' isn't valid", argDef.Name)
+			}
+		} else if argDef.Type == ArgString {
+			_, ok := arg.(string)
+			if !ok {
+				return fmt.Errorf("Argument '%s' must be a string", argDef.Name)
+			}
+		}
+	}
+
+	return nil
+}
+
 func (r *request) ConvertOptions(options map[string]Option) error {
 	converted := make(map[string]interface{})