generalize ValidArgs; use it implicitly with any validator (spf13#841)

.travis.yml

@@ -14,6 +14,9 @@ before_install:
   - go get -u github.com/kyoh86/richgo
   - go get -u github.com/mitchellh/gox
 
+env:
+  - GO111MODULE=on
+
 matrix:
   allow_failures:
     - go: tip
@@ -25,5 +28,5 @@ matrix:
       go: 1.13.x
       script: make cobra_generator
 
-script: 
+script:
  - make test

README.md

@@ -428,28 +428,32 @@ rootCmd.MarkPersistentFlagRequired("region")
 ## Positional and Custom Arguments
 
 Validation of positional arguments can be specified using the `Args` field
-of `Command`.
+of `Command`. The following validators are built in:
 
-The following validators are built in:
+- `NoArgs` - report an error if there are any positional args.
+- `ArbitraryArgs` - accept any args.
+- `MinimumNArgs(int)` - report an error if less than N positional args are provided.
+- `MaximumNArgs(int)` - report an error if more than N positional args are provided.
+- `ExactArgs(int)` - report an error if there are not exactly N positional args.
+- `RangeArgs(min, max)` - report an error if the number of args is not between `min` and `max`.
 
-- `NoArgs` - the command will report an error if there are any positional args.
-- `ArbitraryArgs` - the command will accept any args.
-- `OnlyValidArgs` - the command will report an error if there are any positional args that are not in the `ValidArgs` field of `Command`.
-- `MinimumNArgs(int)` - the command will report an error if there are not at least N positional args.
-- `MaximumNArgs(int)` - the command will report an error if there are more than N positional args.
-- `ExactArgs(int)` - the command will report an error if there are not exactly N positional args.
-- `ExactValidArgs(int)` - the command will report an error if there are not exactly N positional args OR if there are any positional args that are not in the `ValidArgs` field of `Command`
-- `RangeArgs(min, max)` - the command will report an error if the number of args is not between the minimum and maximum number of expected args.
+If `Args` is undefined or `nil`, it defaults to `ArbitraryArgs`.
 
-An example of setting the custom validator:
+Field `ValidArgs` of type `[]string` can be defined in `Command`, in order to report an error if there are any positional args that are not in the list. This validation is executed implicitly before the validator defined in `Args`.
+
+> NOTE: `OnlyValidArgs` and `ExactValidArgs(int)` are now deprecated. `ArbitraryArgs` and `ExactArgs(int)` provide the same functionality now.
+
+Moreover, it is possible to set any custom validator that satisfies `func(cmd *cobra.Command, args []string) error`. For example:
 
 ```go
 var cmd = &cobra.Command{
   Short: "hello",
   Args: func(cmd *cobra.Command, args []string) error {
-    if len(args) < 1 {
-      return errors.New("requires a color argument")
+    // Optionally run one of the validators provided by cobra
+    if err := cobra.MinimumNArgs(1)(cmd, args); err != nil {
+        return err
     }
+    // Run the custom validation logic
     if myapp.IsValidColor(args[0]) {
       return nil
     }

args.go

@@ -7,6 +7,25 @@ import (
 
 type PositionalArgs func(cmd *Command, args []string) error
 
+// validateArgs returns an error if there are any positional args that are not in
+// the `ValidArgs` field of `Command`
+func validateArgs(cmd *Command, args []string) error {
+	if len(cmd.ValidArgs) > 0 {
+		// Remove any description that may be included in ValidArgs.
+		// A description is following a tab character.
+		var validArgs []string
+		for _, v := range cmd.ValidArgs {
+			validArgs = append(validArgs, strings.Split(v, "\t")[0])
+		}
+		for _, v := range args {
+			if !stringInSlice(v, validArgs) {
+				return fmt.Errorf("invalid argument %q for %q%s", v, cmd.CommandPath(), cmd.findSuggestions(args[0]))
+			}
+		}
+	}
+	return nil
+}
+
 // Legacy arg validation has the following behaviour:
 // - root commands with no subcommands can take arbitrary arguments
 // - root commands with subcommands will do subcommand validity checking
@@ -32,25 +51,6 @@ func NoArgs(cmd *Command, args []string) error {
 	return nil
 }
 
-// OnlyValidArgs returns an error if any args are not in the list of ValidArgs.
-func OnlyValidArgs(cmd *Command, args []string) error {
-	if len(cmd.ValidArgs) > 0 {
-		// Remove any description that may be included in ValidArgs.
-		// A description is following a tab character.
-		var validArgs []string
-		for _, v := range cmd.ValidArgs {
-			validArgs = append(validArgs, strings.Split(v, "\t")[0])
-		}
-
-		for _, v := range args {
-			if !stringInSlice(v, validArgs) {
-				return fmt.Errorf("invalid argument %q for %q%s", v, cmd.CommandPath(), cmd.findSuggestions(args[0]))
-			}
-		}
-	}
-	return nil
-}
-
 // ArbitraryArgs never returns an error.
 func ArbitraryArgs(cmd *Command, args []string) error {
 	return nil
@@ -86,18 +86,6 @@ func ExactArgs(n int) PositionalArgs {
 	}
 }
 
-// ExactValidArgs returns an error if
-// there are not exactly N positional args OR
-// there are any positional args that are not in the `ValidArgs` field of `Command`
-func ExactValidArgs(n int) PositionalArgs {
-	return func(cmd *Command, args []string) error {
-		if err := ExactArgs(n)(cmd, args); err != nil {
-			return err
-		}
-		return OnlyValidArgs(cmd, args)
-	}
-}
-
 // RangeArgs returns an error if the number of args is not within the expected range.
 func RangeArgs(min int, max int) PositionalArgs {
 	return func(cmd *Command, args []string) error {
@@ -107,3 +95,18 @@ func RangeArgs(min int, max int) PositionalArgs {
 		return nil
 	}
 }
+
+// ExactValidArgs returns an error if there are not exactly N positional args OR
+// there are any positional args that are not in the `ValidArgs` field of `Command`
+//
+// Deprecated: now `ExactArgs` honors `ValidArgs`, when defined and not empty
+func ExactValidArgs(n int) PositionalArgs {
+	return ExactArgs(n)
+}
+
+// OnlyValidArgs returns an error if any args are not in the list of `ValidArgs`.
+//
+// Deprecated: now `ArbitraryArgs` honors `ValidArgs`, when defined and not empty
+func OnlyValidArgs(cmd *Command, args []string) error {
+	return ArbitraryArgs(cmd, args)
+}