Field rules

FieldRules encapsulates the rules for each type of field. Depending on the field, the correct set should be used to ensure proper validations.

cel

cel is a repeated field used to represent a textual expression in the Common Expression Language (CEL) syntax. For more information on CEL, see our documentation.

field.cel example

message MyMessage {
  // The field `value` must be greater than 42.
  optional int32 value = 1 [(buf.validate.field).cel = {
    id: "my_message.value",
    message: "value must be greater than 42",
    expression: "this > 42",
  }];
}

required

If required is true, the field must be populated. A populated field can be described as "serialized in the wire format," which includes:

• the following "nullable" fields must be explicitly set to be considered populated:
  • singular message fields (whose fields may be unpopulated/default values)
  • member fields of a oneof (may be their default value)
  • proto3 optional fields (may be their default value)
  • proto2 scalar fields (both optional and required)
• proto3 scalar fields must be non-zero to be considered populated
• repeated and map fields must be non-empty to be considered populated

field.required example

message MyMessage {
  // The field `value` must be set to a non-null value.
  optional MyOtherMessage value = 1 [(buf.validate.field).required = true];
}

ignore

Skip validation on the field if its value matches the specified criteria. See Ignore enum for details.

field.ignore example

message UpdateRequest {
  // The uri rule only applies if the field is populated and not an empty
  // string.
  optional string url = 1 [
    (buf.validate.field).ignore = IGNORE_IF_DEFAULT_VALUE,
    (buf.validate.field).string.uri = true,
  ];
}