implement ValidateNil method for NotBlankConstraint and BlankConstraint; update test cases to include nil type

Author: Igor Lazarev

.golangci.yml

@@ -156,6 +156,7 @@ linters:
           - errorlint
         path: validationtest/assertion.go
     paths:
+      - var
       - third_party$
       - builtin$
       - examples$

it/basic.go

@@ -71,6 +71,20 @@ func (c NotBlankConstraint[T]) WithMessage(template string, parameters ...valida
 	return c
 }
 
+func (c NotBlankConstraint[T]) ValidateNil(ctx context.Context, validator *validation.Validator, isNil bool) error {
+	if c.isIgnored || validator.IsIgnoredForGroups(c.groups...) {
+		return nil
+	}
+	if c.allowNil && isNil {
+		return nil
+	}
+	if !isNil {
+		return nil
+	}
+
+	return c.newViolation(ctx, validator)
+}
+
 func (c NotBlankConstraint[T]) ValidateBool(ctx context.Context, validator *validation.Validator, value *bool) error {
 	if c.isIgnored || validator.IsIgnoredForGroups(c.groups...) {
 		return nil
@@ -202,6 +216,14 @@ func (c BlankConstraint[T]) WithMessage(template string, parameters ...validatio
 	return c
 }
 
+func (c BlankConstraint[T]) ValidateNil(ctx context.Context, validator *validation.Validator, isNil bool) error {
+	if c.isIgnored || validator.IsIgnoredForGroups(c.groups...) || isNil {
+		return nil
+	}
+
+	return c.newViolation(ctx, validator)
+}
+
 func (c BlankConstraint[T]) ValidateBool(ctx context.Context, validator *validation.Validator, value *bool) error {
 	if c.isIgnored || validator.IsIgnoredForGroups(c.groups...) || value == nil || !*value {
 		return nil

test/constraints_basic_cases_test.go

@@ -11,7 +11,7 @@ import (
 var isNotBlankConstraintTestCases = []ConstraintValidationTestCase{
 	{
 		name:            "IsNotBlank violation on nil",
-		isApplicableFor: specificValueTypes(boolType, stringType, countableType, timeType),
+		isApplicableFor: specificValueTypes(nilType, boolType, stringType, countableType, timeType),
 		constraint:      it.IsNotBlank(),
 		assert:          assertHasOneViolation(validation.ErrIsBlank, message.IsBlank),
 	},
@@ -43,7 +43,7 @@ var isNotBlankConstraintTestCases = []ConstraintValidationTestCase{
 	},
 	{
 		name:            "IsNotBlank violation on nil with custom message",
-		isApplicableFor: specificValueTypes(boolType, stringType, countableType, timeType),
+		isApplicableFor: specificValueTypes(nilType, boolType, stringType, countableType, timeType),
 		constraint: it.IsNotBlank().
 			WithError(ErrCustom).
 			WithMessage(
@@ -54,7 +54,7 @@ var isNotBlankConstraintTestCases = []ConstraintValidationTestCase{
 	},
 	{
 		name:            "IsNotBlank passes on value",
-		isApplicableFor: specificValueTypes(boolType, stringType, countableType, timeType),
+		isApplicableFor: specificValueTypes(nilType, boolType, stringType, countableType, timeType),
 		boolValue:       boolValue(true),
 		intValue:        intValue(1),
 		floatValue:      floatValue(0.1),
@@ -68,19 +68,19 @@ var isNotBlankConstraintTestCases = []ConstraintValidationTestCase{
 	},
 	{
 		name:            "IsNotBlank passes on nil when allowed",
-		isApplicableFor: specificValueTypes(boolType, stringType, timeType),
+		isApplicableFor: specificValueTypes(nilType, boolType, stringType, timeType),
 		constraint:      it.IsNotBlank().WithAllowedNil(),
 		assert:          assertNoError,
 	},
 	{
 		name:            "IsNotBlank passes on nil when condition is false",
-		isApplicableFor: specificValueTypes(boolType, stringType, timeType),
+		isApplicableFor: specificValueTypes(nilType, boolType, stringType, timeType),
 		constraint:      it.IsNotBlank().When(false),
 		assert:          assertNoError,
 	},
 	{
 		name:            "IsNotBlank passes on nil when groups not match",
-		isApplicableFor: specificValueTypes(boolType, stringType, timeType),
+		isApplicableFor: specificValueTypes(nilType, boolType, stringType, timeType),
 		constraint:      it.IsNotBlank().WhenGroups(testGroup),
 		assert:          assertNoError,
 	},
@@ -239,7 +239,7 @@ var isBlankConstraintTestCases = []ConstraintValidationTestCase{
 	},
 	{
 		name:            "IsBlank passes on nil",
-		isApplicableFor: specificValueTypes(boolType, stringType, countableType, timeType),
+		isApplicableFor: specificValueTypes(nilType, boolType, stringType, countableType, timeType),
 		constraint:      it.IsBlank(),
 		assert:          assertNoError,
 	},
@@ -259,7 +259,7 @@ var isBlankConstraintTestCases = []ConstraintValidationTestCase{
 	},
 	{
 		name:            "IsBlank passes on value when condition is false",
-		isApplicableFor: specificValueTypes(boolType, stringType, countableType, timeType),
+		isApplicableFor: specificValueTypes(nilType, boolType, stringType, countableType, timeType),
 		boolValue:       boolValue(true),
 		intValue:        intValue(1),
 		floatValue:      floatValue(0.1),
@@ -273,7 +273,7 @@ var isBlankConstraintTestCases = []ConstraintValidationTestCase{
 	},
 	{
 		name:            "IsBlank passes on value when groups not match",
-		isApplicableFor: specificValueTypes(boolType, stringType, countableType, timeType),
+		isApplicableFor: specificValueTypes(nilType, boolType, stringType, countableType, timeType),
 		boolValue:       boolValue(true),
 		intValue:        intValue(1),
 		floatValue:      floatValue(0.1),