Validation: add WithMessage

Author: System-Glitch

lang/lang_test.go

@@ -97,8 +97,9 @@ func (suite *LangTestSuite) TestLoad() {
 		},
 		validation: validationLines{
 			rules: map[string]string{
-				"override":       "rule override",
-				"required.array": "The :field values are required.",
+				"override":        "rule override",
+				"required.array":  "The :field values are required.",
+				"messageOverride": "Custom error message: placeholders work: ':field', :min - :max",
 			},
 			fields: map[string]string{
 				"email": "email address",

middleware_test.go

@@ -245,8 +245,8 @@ func TestLanguageMiddleware(t *testing.T) {
 }
 
 type testValidator struct {
-	validation.BaseValidator
 	validateFunc func(c *testValidator, ctx *validation.Context) bool
+	validation.BaseValidator
 }
 
 func (v *testValidator) Validate(ctx *validation.Context) bool {

resources/lang/en-US/rules.json

@@ -1,4 +1,5 @@
 {
     "override": "rule override",
-    "required.array": "The :field values are required."
+    "required.array": "The :field values are required.",
+    "messageOverride": "Custom error message: placeholders work: ':field', :min - :max"
 }

validation/comparison.go

@@ -16,8 +16,8 @@ import (
 //   - Compare the number of keys in an object with a numeric field
 //   - Compare a file (or multifile) size with a numeric field. The number of KiB of each file is rounded up (ceil).
 type ComparisonValidator struct {
-	BaseValidator
 	Path *walk.Path
+	BaseValidator
 }
 
 // Validate checks the field under validation satisfies this validator's criteria.

validation/date.go

@@ -62,8 +62,8 @@ func Date(acceptedFormats ...string) *DateValidator {
 
 // DateComparisonValidator factorized date comparison validator for static dates (before, after, etc.)
 type DateComparisonValidator struct {
-	BaseValidator
 	Date time.Time
+	BaseValidator
 }
 
 func (v *DateComparisonValidator) validate(ctx *Context, comparisonFunc func(time.Time, time.Time) bool) bool {
@@ -85,8 +85,8 @@ func (v *DateComparisonValidator) MessagePlaceholders(_ *Context) []string {
 
 // DateFieldComparisonValidator factorized date comparison validator for field dates (before field, after field, etc.)
 type DateFieldComparisonValidator struct {
-	BaseValidator
 	Path *walk.Path
+	BaseValidator
 }
 
 func (v *DateFieldComparisonValidator) validate(ctx *Context, comparisonFunc func(time.Time, time.Time) bool) bool {

validation/different.go

@@ -14,8 +14,8 @@ import (
 // For numbers, make sure the two compared numbers have the same type. A `uint` with value `1` will be considered
 // different from an `int` with value `1`.
 type DifferentValidator struct {
-	BaseValidator
 	Path *walk.Path
+	BaseValidator
 }
 
 // Validate checks the field under validation satisfies this validator's criteria.

validation/in.go

@@ -83,8 +83,8 @@ func NotIn[T comparable](values []T) *NotInValidator[T] {
 // InFieldValidator validates the field under validation must be in at least one
 // of the arrays matched by the specified path.
 type InFieldValidator[T comparable] struct {
-	BaseValidator
 	Path *walk.Path
+	BaseValidator
 }
 
 // Validate checks the field under validation satisfies this validator's criteria.

validation/regex.go

@@ -5,8 +5,8 @@ import "regexp"
 // RegexValidator the field under validation must be a string matching
 // the specified `*regexp.Regexp`.
 type RegexValidator struct {
-	BaseValidator
 	Regexp *regexp.Regexp
+	BaseValidator
 }
 
 // Validate checks the field under validation satisfies this validator's criteria.

validation/required.go

@@ -36,8 +36,8 @@ func Required() *RequiredValidator {
 // RequiredIfValidator is the same as `RequiredValidator` but only applies the behavior
 // described if the specified `Condition` function returns true.
 type RequiredIfValidator struct {
-	RequiredValidator
 	Condition func(*Context) bool
+	RequiredValidator
 }
 
 // Validate checks the field under validation satisfies this validator's criteria.

validation/ruleset.go

@@ -55,12 +55,16 @@ type Validator interface {
 	// This is use to generate the validation error message. An empty slice can be returned.
 	// See `lang.Language.Get()` for more details.
 	MessagePlaceholders(ctx *Context) []string
+
+	overrideMessage(langEntry string)
+	getMessageOverride() string
 }
 
 // BaseValidator composable structure that implements the basic functions required to
 // satisfy the `Validator` interface.
 type BaseValidator struct {
 	component
+	messageOverride string
 }
 
 func (v *BaseValidator) init(options *Options) {
@@ -86,6 +90,22 @@ func (v *BaseValidator) IsType() bool { return false }
 // MessagePlaceholders returns an empty slice (no placeholders)
 func (v *BaseValidator) MessagePlaceholders(_ *Context) []string { return []string{} }
 
+func (v *BaseValidator) overrideMessage(langEntry string) {
+	v.messageOverride = langEntry
+}
+
+func (v *BaseValidator) getMessageOverride() string {
+	return v.messageOverride
+}
+
+// WithMessage set a custom language entry for the error message of a Validator.
+// Original placeholders returned by the validator are still used to render the message.
+// Type-dependent and "element" suffixes are not added when the message is overridden.
+func WithMessage[V Validator](v V, langEntry string) V {
+	v.overrideMessage(langEntry)
+	return v
+}
+
 // FieldRulesConverter types implementing this interface define their behavior
 // when converting a `FieldRules` to `Rules`. This enables rule sets composition.
 type FieldRulesConverter interface {