ValidationIssue and IssueCode

A ValidationIssue is one problem found during validation. Issues are the source of every other error view: messages, errors and getError are derived from them.

ValidationIssue

Member	Type	Meaning
`code`	`IssueCode`	The kind of problem.
`path`	`List<Object>`	Where the problem is: schema field keys and map keys as `String`, list indices as `int`. Empty for the validated value itself.
`errorPath`	`String`	`path` joined with dots, such as `items.1.id`. `''` for the value itself.
`message`	`String`	The error message, after `message`, `messageBuilder` and `l.messageBuilder` have been applied.
`params`	`Map<String, Object?>`	The values that describe the problem, such as `{'min': 3}`. Each code documents its params below.
`fieldName`	`String?`	The name used in default messages: the field key inside a schema, or the `withName` name, or `null`.
`withMessage(String)`	`ValidationIssue`	A copy with the message replaced.

final issue = l.int().min(18).withName('age').validate(12).issues.single;

print(issue.code);
print(issue.code.name);
print(issue.path);
print(issue.errorPath);
print(issue.message);
print(issue.params);
print(issue.fieldName);

tooSmall
tooSmall
[]

age must be greater than or equal to 18
{min: 18}
age

toString() prints the code, the path and the message:

ValidationIssue(code: tooSmall, path: , message: age must be greater than or equal to 18)

IssueCode

IssueCode is an extension type over a String, so it compares by name and can be used in a switch. The set is open: a minor release may add codes, so always include a default case.

switch (issue.code) {
  case IssueCode.tooSmall:
    print('too small');
  case IssueCode.invalidType:
    print('wrong type');
  case IssueCode.required:
    print('missing');
  default:
    print('other');
}

too small
wrong type
missing

Every code, the validation that produces it, and the params it sets:

Code	Produced by	Params
`required`	`.required()` on `null` or a missing field; `validateSchema(null)`
`invalidType`	Every type: `l.string()`, `l.int()`, `l.double()`, `l.num()`, `l.bool()`, `l.list()`, `l.map()`, `l.schema()`, `l.file()`, `l.nullValue()`; also a map key or value that fails its type argument	`expected`, the type name such as `'string'`
`tooSmall`	number `.min(n)`	`min`
`tooBig`	number `.max(n)`	`max`
`notFinite`	`.finite()`
`tooShort`	string `.min(n)`	`min`
`tooLong`	string `.max(n)`	`max`
`invalidLength`	`.length(n)`	`length`
`invalidEmail`	`.email()`
`invalidDateTime`	`.dateTime()`
`invalidUri`	`.uri()`	`allowedSchemes`
`invalidUrl`	`.url()`	`allowedSchemes`
`invalidEmoji`	`.emoji()`
`invalidUuid`	`.uuid()`
`invalidCuid`	`.cuid()`
`invalidCuid2`	`.cuid2()`
`invalidIp`	`.ip()`	`version`, an `IpVersion?`
`invalidPattern`	`.regex(p)`	`pattern`, the source string
`missingPrefix`	`.startsWith(s)`	`prefix`
`missingSuffix`	`.endsWith(s)`	`suffix`
`missingSubstring`	`.contains(s)`	`substring`
`notOneOf`	`l.oneOf([...])`	`allowed`, the list of values
`invalidUnion`	`l.union([...])` when no option passes	`issues`, a `List<List<ValidationIssue>>`, one list per option
`invalidKey`	`l.map()` when a key fails its key validator; reported at the map’s path	`key`, and `issues`, the key validator’s issues
`unrecognizedKey`	`.strict()` for each unknown key; reported at the key’s path	`key`
`custom`	`.custom()` and `.customWithSchema()` when the function returns `false` or throws
`tooDeep`	Nesting deeper than `l.maxDepth`	`maxDepth`
`fromJsonFailed`	`validateSchema` when `fromJson` throws	`error`, the thrown object

The default message for each code is on Error messages.