Feature: Add check for overlapping xor and and groups (#443)

* Docs: Clean and group description

* Feat: Add check for overlapping xor and and groups

Co-authored-by: inful <[email protected]>

* Chore: Rewrite overlap err to avoid duplicated words

---------

Co-authored-by: inful <[email protected]>

Author: tinytyranid

Diff for: README.md

@@ -577,7 +577,7 @@ Both can coexist with standard Tag parsing.
 | `enum:"X,Y,..."`     | Set of valid values allowed for this flag. An enum field must be `required` or have a valid `default`.                                                                                                                                                                                                                         |
 | `group:"X"`          | Logical group for a flag or command.                                                                                                                                                                                                                                                                                           |
 | `xor:"X,Y,..."`      | Exclusive OR groups for flags. Only one flag in the group can be used which is restricted within the same command. When combined with `required`, at least one of the `xor` group will be required.                                                                                                                            |
-| `and:"X,Y,..."`      | Exclusive AND groups for flags. All flags in the group must be used in the same command. When combined with `required`, all flags in the group will be required.                                                                                                                                                               |
+| `and:"X,Y,..."`      | AND groups for flags. All flags in the group must be used in the same command. When combined with `required`, all flags in the group will be required.                                                                                                                                                                         |
 | `prefix:"X"`         | Prefix for all sub-flags.                                                                                                                                                                                                                                                                                                      |
 | `envprefix:"X"`      | Envar prefix for all sub-flags.                                                                                                                                                                                                                                                                                                |
 | `set:"K=V"`          | Set a variable for expansion by child elements. Multiples can occur.                                                                                                                                                                                                                                                           |

Diff for: kong.go

@@ -167,9 +167,42 @@ func New(grammar interface{}, options ...Option) (*Kong, error) {
 
 	k.bindings.add(k.vars)
 
+	if err = checkOverlappingXorAnd(k); err != nil {
+		return nil, err
+	}
+
 	return k, nil
 }
 
+func checkOverlappingXorAnd(k *Kong) error {
+	xorGroups := map[string][]string{}
+	andGroups := map[string][]string{}
+	for _, flag := range k.Model.Node.Flags {
+		for _, xor := range flag.Xor {
+			xorGroups[xor] = append(xorGroups[xor], flag.Name)
+		}
+		for _, and := range flag.And {
+			andGroups[and] = append(andGroups[and], flag.Name)
+		}
+	}
+	for xor, xorSet := range xorGroups {
+		for and, andSet := range andGroups {
+			overlappingEntries := []string{}
+			for _, xorTag := range xorSet {
+				for _, andTag := range andSet {
+					if xorTag == andTag {
+						overlappingEntries = append(overlappingEntries, xorTag)
+					}
+				}
+			}
+			if len(overlappingEntries) > 1 {
+				return fmt.Errorf("invalid xor and combination, %s and %s overlap with more than one: %s", xor, and, overlappingEntries)
+			}
+		}
+	}
+	return nil
+}
+
 type varStack []Vars
 
 func (v *varStack) head() Vars { return (*v)[len(*v)-1] }

Diff for: kong_test.go

@@ -1026,6 +1026,16 @@ func TestXorAnd(t *testing.T) {
 	assert.EqualError(t, err, "--hello and --one can't be used together, --hello and --two must be used together")
 }
 
+func TestOverLappingXorAnd(t *testing.T) {
+	var cli struct {
+		Hello bool   `xor:"one" and:"two"`
+		One   bool   `xor:"one" and:"two"`
+		Two   string `xor:"one" and:"two"`
+	}
+	_, err := kong.New(&cli)
+	assert.EqualError(t, err, "invalid xor and combination, one and two overlap with more than one: [hello one two]")
+}
+
 func TestXorRequired(t *testing.T) {
 	var cli struct {
 		One   bool `xor:"one,two" required:""`