Add contains tag

README.md

@@ -129,6 +129,7 @@ You set the validation rules following the "validate:" tag according to the rule
 | alphanumeric     | Check whether value is alphanumeric or not        |
 | ascii             | Check whether value is ASCII or not                |
 | boolean           | Check whether value is boolean or not.           |
+| contains          | Check whether value contains the specified substring <br> e.g. `validate:"contains=abc"` |
 | lowercase         | Check whether value is lowercase or not           |
 | numeric           | Check whether value is numeric or not              |
 | uppercase         | Check whether value is uppercase or not           |

csv_test.go

@@ -565,4 +565,62 @@ badあ@example.com
 			}
 		}
 	})
+
+	t.Run("validate contains", func(t *testing.T) {
+		t.Parallel()
+
+		input := `name
+search for a needle in a haystack
+example sentence
+`
+
+		c, err := NewCSV(bytes.NewBufferString(input))
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		type contains struct {
+			Name string `validate:"contains=needle"`
+		}
+
+		containsList := make([]contains, 0)
+		errs := c.Decode(&containsList)
+		for i, err := range errs {
+			switch i {
+			case 0:
+				if err.Error() != "line:3 column name: target does not contain the specified value: contains=needle, value=example sentence" {
+					t.Errorf("CSV.Decode() got errors: %v", err)
+				}
+			}
+		}
+	})
+
+	t.Run("invalid contains tag format", func(t *testing.T) {
+		t.Parallel()
+
+		input := `name
+search for a needle in a haystack
+example sentence
+`
+
+		c, err := NewCSV(bytes.NewBufferString(input))
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		type contains struct {
+			Name string `validate:"contains=needle bad_value"`
+		}
+
+		containsList := make([]contains, 0)
+		errs := c.Decode(&containsList)
+		for i, err := range errs {
+			switch i {
+			case 0:
+				if err.Error() != "target is not one of the values: contains=needle bad_value" {
+					t.Errorf("CSV.Decode() got errors: %v", err)
+				}
+			}
+		}
+	})
 }

errors.go

@@ -98,4 +98,8 @@ var (
 	ErrASCIIID = "ErrASCII"
 	// ErrEmailID is the error ID used when the target is not an email.
 	ErrEmailID = "ErrEmail"
+	// ErrContainsID is the error ID used when the target does not contain the specified value.
+	ErrContainsID = "ErrContains"
+	// ErrInvalidContainsFormatID is the error ID used when the contains format is invalid.
+	ErrInvalidContainsFormatID = "ErrInvalidContainsFormat"
 )

i18n/en.yaml

@@ -69,3 +69,9 @@
 
 - id: "ErrEmail"
   translation: "target is not a valid email address"
+
+- id: "ErrContains"
+  translation: "target does not contain the specified value"
+
+- id: "ErrInvalidContainsFormat"
+  translation: "'contains' tag format is invalid"

i18n/ja.yaml

@@ -75,3 +75,9 @@
 
 - id: "ErrEmail"
   translation: "値がメールアドレスではありません"
+
+- id: "ErrContains"
+  translation: "指定された値を含んでいません"
+
+- id: "ErrInvalidContainsFormat"
+  translation: "'contains'タグの形式が無効です"

i18n/ru.yaml

@@ -69,3 +69,9 @@
 
 - id: "ErrEmail"
   translation: "целевое значение не является адресом электронной почты"
+
+- id: "ErrContains"
+  translation: "целевое значение не содержит подстроку"
+
+- id: "ErrInvalidContains"
+  translation: "Формат тега 'contains' недопустим"

parser.go

@@ -135,6 +135,15 @@ func (c *CSV) parseValidateTag(tags string) (validators, error) {
 			validatorList = append(validatorList, newASCIIValidator())
 		case strings.HasPrefix(t, emailTagValue.String()):
 			validatorList = append(validatorList, newEmailValidator())
+		case strings.HasPrefix(t, containsTagValue.String()):
+			oneOf, err := c.parseOneOf(t)
+			if err != nil {
+				return nil, err
+			}
+			if len(oneOf) != 1 {
+				return nil, NewError(c.i18nLocalizer, ErrInvalidOneOfFormatID, t)
+			}
+			validatorList = append(validatorList, newContainsValidator(oneOf[0]))
 		}
 	}
 	return validatorList, nil

tag.go

@@ -50,6 +50,8 @@ const (
 	asciiTagValue tagValue = "ascii"
 	// emailTagValue is the struct tag name for email fields.
 	emailTagValue tagValue = "email"
+	// containsTagValue is the struct tag name for contains fields.
+	containsTagValue tagValue = "contains"
 )
 
 // String returns the string representation of the tag.

validation.go

@@ -502,3 +502,26 @@ func (e *emailValidator) Do(localizer *i18n.Localizer, target any) error {
 	}
 	return nil
 }
+
+// containsValidator is a struct that contains the validation rules for a contains column.
+type containsValidator struct {
+	contains string
+}
+
+// newContainsValidator returns a new containsValidator.
+func newContainsValidator(contains string) *containsValidator {
+	return &containsValidator{contains: contains}
+}
+
+// Do validates the target contains the contains value.
+func (c *containsValidator) Do(localizer *i18n.Localizer, target any) error {
+	v, ok := target.(string)
+	if !ok {
+		return NewError(localizer, ErrContainsID, fmt.Sprintf("value=%v", target))
+	}
+
+	if !strings.Contains(v, c.contains) {
+		return NewError(localizer, ErrContainsID, fmt.Sprintf("contains=%s, value=%v", c.contains, target))
+	}
+	return nil
+}