Expose the struct the field is contained within

This allows users of `FieldError` to be able to query information about
the struct the field is contained within. This information can then be
used to work out what to display when the param field points to another
field, such as with `gtfield`, and a tag name function has been
registered.

errors.go

@@ -158,6 +158,9 @@ type FieldError interface {
 
 	// Error returns the FieldError's message
 	Error() string
+
+	// Parent returns the Type of the struct that the StructField is contained within
+	Parent() reflect.Type
 }
 
 // compile time interface checks
@@ -179,6 +182,7 @@ type fieldError struct {
 	param          string
 	kind           reflect.Kind
 	typ            reflect.Type
+	parent         reflect.Type
 }
 
 // Tag returns the validation tag that failed.
@@ -254,6 +258,11 @@ func (fe *fieldError) Error() string {
 	return fmt.Sprintf(fieldErrMsg, fe.ns, fe.Field(), fe.tag)
 }
 
+// Parent returns the Type of the struct that the StructField is contained within
+func (fe *fieldError) Parent() reflect.Type {
+	return fe.parent
+}
+
 // Translate returns the FieldError's translated error
 // from the provided 'ut.Translator' and registered 'TranslationFunc'
 //

validator.go

@@ -154,6 +154,7 @@ func (v *validate) traverseField(ctx context.Context, parent reflect.Value, curr
 						param:          ct.param,
 						kind:           kind,
 						typ:            current.Type(),
+						parent:         parent.Type(),
 					},
 				)
 				return
@@ -199,6 +200,7 @@ func (v *validate) traverseField(ctx context.Context, parent reflect.Value, curr
 								param:          ct.param,
 								kind:           kind,
 								typ:            typ,
+								parent:         parent.Type(),
 							},
 						)
 						return
@@ -413,6 +415,7 @@ OUTER:
 								param:          ct.param,
 								kind:           kind,
 								typ:            typ,
+								parent:         parent.Type(),
 							},
 						)
 
@@ -433,6 +436,7 @@ OUTER:
 								param:          ct.param,
 								kind:           kind,
 								typ:            typ,
+								parent:         parent.Type(),
 							},
 						)
 					}
@@ -474,6 +478,7 @@ OUTER:
 						param:          ct.param,
 						kind:           kind,
 						typ:            typ,
+						parent:         parent.Type(),
 					},
 				)
 

validator_test.go

@@ -367,6 +367,7 @@ func TestStructLevelInvalidError(t *testing.T) {
 	Equal(t, fe.ActualTag(), "required")
 	Equal(t, fe.Kind(), reflect.Invalid)
 	Equal(t, fe.Type(), reflect.TypeOf(nil))
+	Equal(t, fe.Parent(), reflect.TypeOf(nil))
 }
 
 func TestNameNamespace(t *testing.T) {
@@ -8624,6 +8625,7 @@ func TestStructSliceValidation(t *testing.T) {
 	Equal(t, fe.Param(), "10")
 	Equal(t, fe.Kind(), reflect.Slice)
 	Equal(t, fe.Type(), reflect.TypeOf([]int{}))
+	Equal(t, fe.Parent(), reflect.TypeOf(TestSlice{}))
 
 	_, ok := fe.Value().([]int)
 	Equal(t, ok, true)