github.com/kaptinlin/jsonschema@v0.4.6/maxlength.go (about)

     1  package jsonschema
     2  
     3  import (
     4  	"fmt"
     5  	"unicode/utf8"
     6  )
     7  
     8  // EvaluateMaxLength checks if the length of a string instance does not exceed the maxLength specified in the schema.
     9  // According to the JSON Schema Draft 2020-12:
    10  //   - The "maxLength" keyword must be a non-negative integer.
    11  //   - A string instance is valid against this keyword if its length is less than or equal to the value of this keyword.
    12  //   - The length of a string instance is defined as the number of its characters as defined by RFC 8259.
    13  //
    14  // This method ensures that the string data instance does not exceed the maximum length defined in the schema.
    15  // If the instance exceeds this length, it returns a EvaluationError detailing the maximum allowed length and the actual length.
    16  //
    17  // Reference: https://json-schema.org/draft/2020-12/json-schema-validation#name-maxlength
    18  func evaluateMaxLength(schema *Schema, value string) *EvaluationError {
    19  	if schema.MaxLength != nil {
    20  		// Use utf8.RuneCountInString to correctly count the number of graphemes in the string
    21  		length := utf8.RuneCountInString(value)
    22  		if length > int(*schema.MaxLength) {
    23  			// String exceeds the maximum length.
    24  			return NewEvaluationError("maxLength", "string_too_long", "Value should be at most {max_length} characters", map[string]interface{}{
    25  				"max_length": fmt.Sprintf("%.0f", *schema.MaxLength),
    26  				"length":     length,
    27  			})
    28  		}
    29  	}
    30  	return nil
    31  }