feat(validation): adds support for patternDescription tag for human-r…

…eadable validation messages when using patterns

schema.go

@@ -77,6 +77,7 @@ type Schema struct {
 	MinLength            *int                `yaml:"minLength,omitempty"`
 	MaxLength            *int                `yaml:"maxLength,omitempty"`
 	Pattern              string              `yaml:"pattern,omitempty"`
+	PatternDescription   string              `yaml:"patternDescription,omitempty"`
 	MinItems             *int                `yaml:"minItems,omitempty"`
 	MaxItems             *int                `yaml:"maxItems,omitempty"`
 	UniqueItems          bool                `yaml:"uniqueItems,omitempty"`
@@ -187,7 +188,11 @@ func (s *Schema) PrecomputeMessages() {
 	}
 	if s.Pattern != "" {
 		s.patternRe = regexp.MustCompile(s.Pattern)
-		s.msgPattern = "expected string to match pattern " + s.Pattern
+		if s.PatternDescription != "" {
+			s.msgPattern = "expected string to be " + s.PatternDescription
+		} else {
+			s.msgPattern = "expected string to match pattern " + s.Pattern
+		}
 	}
 	if s.MinItems != nil {
 		s.msgMinItems = fmt.Sprintf("expected array length >= %d", *s.MinItems)
@@ -498,6 +503,7 @@ func SchemaFromField(registry Registry, f reflect.StructField, hint string) *Sch
 	fs.MinLength = intTag(f, "minLength")
 	fs.MaxLength = intTag(f, "maxLength")
 	fs.Pattern = f.Tag.Get("pattern")
+	fs.PatternDescription = f.Tag.Get("patternDescription")
 	fs.MinItems = intTag(f, "minItems")
 	fs.MaxItems = intTag(f, "maxItems")
 	fs.UniqueItems = boolTag(f, "uniqueItems")

validate_test.go

@@ -265,6 +265,14 @@ var validateTests = []struct {
 		input: map[string]any{"value": "a1"},
 		errs:  []string{"expected string to match pattern ^[a-z]+$"},
 	},
+	{
+		name: "pattern custom message fail",
+		typ: reflect.TypeOf(struct {
+			Value string `json:"value" pattern:"^[a-z]+$" patternDescription:"alphabetical"`
+		}{}),
+		input: map[string]any{"value": "b@2"},
+		errs:  []string{"expected string to be alphabetical"},
+	},
 	{
 		name: "pattern invalid",
 		typ: reflect.TypeOf(struct {