Check that arguments are in ValidArgs

If a command defined cmd.ValidArgs check that the argument is actually
in ValidArgs and fail if it is not.

README.md

@@ -143,6 +143,38 @@ A flag can also be assigned locally which will only apply to that specific comma
 
 	HugoCmd.Flags().StringVarP(&Source, "source", "s", "", "Source directory to read from")
 
+### Specify if you command takes arguments
+
+There are multiple options for how a command can handle unknown arguments which can be set in `TakesArgs`
+- `Legacy`
+- `None`
+- `Arbitrary`
+- `ValidOnly`
+
+`Legacy` (or default) the rules are as follows:
+- root commands with no subcommands can take arbitrary arguments
+- root commands with subcommands will do subcommand validity checking
+- subcommands will always accept arbitrary arguments and do no subsubcommand validity checking
+
+`None` the command will be rejected if there are any left over arguments after parsing flags.
+
+`Arbitrary` any additional values left after parsing flags will be passed in to your `Run` function.
+
+`ValidOnly` you must define all valid (non-subcommand) arguments to your command. These are defined in a slice name ValidArgs. For example a command which only takes the argument "one" or "two" would be defined as:
+
+```go
+var HugoCmd = &cobra.Command{
+        Use:   "hugo",
+        Short: "Hugo is a very fast static site generator",
+	ValidArgs: []string{"one", "two", "three", "four"}
+	TakesArgs: cobra.ValidOnly
+        Run: func(cmd *cobra.Command, args []string) {
+            // args will only have the values one, two, three, four
+	    // or the cmd.Execute() will fail.
+        },
+    }
+```
+
 ### Remove a command from its parent
 
 Removing a command is not a common action in simple programs but it allows 3rd parties to customize an existing command tree.

bash_completions_test.go

@@ -42,11 +42,7 @@ func TestBashCompletions(t *testing.T) {
 	// required flag
 	c.MarkFlagRequired("introot")
 
-	// valid nouns
+	// filename extentions
-	validArgs := []string{"pods", "nodes", "services", "replicationControllers"}
-	c.ValidArgs = validArgs
-
-	// filename
 	var flagval string
 	c.Flags().StringVar(&flagval, "filename", "", "Enter a filename")
 	c.MarkFlagFilename("filename", "json", "yaml", "yml")
@@ -70,10 +66,8 @@ func TestBashCompletions(t *testing.T) {
 	// check for custom completion function
 	check(t, str, `COMPREPLY=( "hello" )`)
 	// check for required nouns
-	check(t, str, `must_have_one_noun+=("pods")`)
+	check(t, str, `must_have_one_noun+=("three")`)
-	// check for filename extension flags
+	// check for filename extention flags
-	check(t, str, `flags_completion+=("_filedir")`)
-	// check for filename extension flags
 	check(t, str, `flags_completion+=("__handle_filename_extension_flag json|yaml|yml")`)
 
 	checkOmit(t, str, cmdDeprecated.Name())

cobra_test.go

@@ -81,7 +81,8 @@ var cmdTimes = &Command{
 	Run: func(cmd *Command, args []string) {
 		tt = args
 	},
-	TakesArgs: Arbitrary,
+	TakesArgs: ValidOnly,
+	ValidArgs: []string{"one", "two", "three", "four"},
 }
 
 var cmdRootNoRun = &Command{
@@ -434,7 +435,7 @@ func TestSubCmdTakesNoArgs(t *testing.T) {
 
 	expectedError := `unknown command "illegal" for "cobra-test deprecated"`
 	if !strings.Contains(result.Error.Error(), expectedError) {
-		t.Errorf("exptected %v, got %v", expectedError, result.Error.Error())
+		t.Errorf("expected %v, got %v", expectedError, result.Error.Error())
 	}
 }
 
@@ -445,6 +446,15 @@ func TestSubCmdTakesArgs(t *testing.T) {
 	}
 }
 
+func TestCmdOnlyValidArgs(t *testing.T) {
+	result := noRRSetupTest("echo times one two five")
+
+	expectedError := `invalid argument "five"`
+	if !strings.Contains(result.Error.Error(), expectedError) {
+		t.Errorf("expected %v, got %v", expectedError, result.Error.Error())
+	}
+}
+
 func TestFlagLong(t *testing.T) {
 	noRRSetupTest("echo --intone=13 something here")
 
@@ -620,9 +630,9 @@ func TestPersistentFlags(t *testing.T) {
 	}
 
 	// persistentFlag should act like normal flag on it's own command
-	fullSetupTest("echo times -s again -c -p test here")
+	fullSetupTest("echo times -s again -c -p one two")
 
-	if strings.Join(tt, " ") != "test here" {
+	if strings.Join(tt, " ") != "one two" {
 		t.Errorf("flags didn't leave proper args remaining..%s given", tt)
 	}
 

command.go

@@ -33,6 +33,7 @@ type Args int
 const (
 	Legacy Args = iota
 	Arbitrary
+	ValidOnly
 	None
 )
 
@@ -383,6 +384,15 @@ func argsMinusFirstX(args []string, x string) []string {
 	return args
 }
 
+func stringInSlice(a string, list []string) bool {
+	for _, b := range list {
+		if b == a {
+			return true
+		}
+	}
+	return false
+}
+
 // find the target command given the args and command tree
 // Meant to be run on the highest node. Only searches down.
 func (c *Command) Find(args []string) (*Command, []string, error) {
@@ -446,6 +456,13 @@ func (c *Command) Find(args []string) (*Command, []string, error) {
 		return commandFound, a, fmt.Errorf("unknown command %q for %q", argsWOflags[0], commandFound.CommandPath())
 	}
 
+	if commandFound.TakesArgs == ValidOnly && len(commandFound.ValidArgs) > 0 {
+		for _, v := range argsWOflags {
+			if !stringInSlice(v, commandFound.ValidArgs) {
+				return commandFound, a, fmt.Errorf("invalid argument %q for %q", v, commandFound.CommandPath())
+			}
+		}
+	}
 	return commandFound, a, nil
 }