standard_schema 0.0.1-dev.0

Standard Schema contracts for Dart validators and converters

standard_schema

Standard Schema contracts for Dart validators and converters.

standard_schema is a Dart port of the contract family described by standardschema.dev. It ports the two official interfaces — StandardSchemaV1 and StandardJSONSchemaV1 — as StandardSchema and StandardJsonSchema, plus a Dart-only combined convenience (StandardSchemaWithJsonSchema) for implementers that satisfy both with one standard getter.

Libraries implement these small surfaces and consumers call them without depending on a vendor-specific schema tree. The package does not define a JSON schema model, parser, renderer, or warning system; those stay in vendor packages (for example, Ack's AckSchemaModel in package:ack).

Implement a schema

import 'package:standard_schema/standard_schema.dart';

final class RequiredStringSchema implements StandardSchema<Object?, String> {
  const RequiredStringSchema();

  @override
  StandardSchemaProps<Object?, String> get standard => StandardSchemaProps(
    vendor: 'example',
    validate: (value, [options]) {
      if (value is String && value.isNotEmpty) {
        return StandardSuccess(value);
      }

      return const StandardFailure([
        StandardIssue(message: 'Expected a non-empty string'),
      ]);
    },
  );
}

Expose JSON Schema conversion

import 'package:standard_schema/standard_schema.dart';

final class RequiredStringJsonSchema
    implements StandardJsonSchema<Object?, String> {
  const RequiredStringJsonSchema();

  @override
  StandardJsonSchemaProps<Object?, String> get standard =>
      StandardJsonSchemaProps(
        vendor: 'example',
        jsonSchema: StandardJsonSchemaConverter(
          input: (options) {
            if (options.target != JsonSchemaTarget.draft07) {
              throw UnsupportedError('Only Draft-7 is supported.');
            }

            return {'type': 'string'};
          },
          output: (options) => {'type': 'string'},
        ),
      );
}

Converters return plain JSON Schema maps (Map<String, Object?>). They may throw when a schema cannot be represented for the requested target.

Implement both traits

StandardSchemaWithJsonSchema is a Dart-only convenience — not a separate upstream interface. It models the structural intersection of the two official ~standard Props when one getter must satisfy both traits.

import 'package:standard_schema/standard_schema.dart';

final class RequiredStringSchemaWithJson
    implements StandardSchemaWithJsonSchema<Object?, String> {
  const RequiredStringSchemaWithJson();

  @override
  StandardSchemaWithJsonSchemaProps<Object?, String> get standard =>
      StandardSchemaWithJsonSchemaProps(
        vendor: 'example',
        validate: (value, [options]) {
          if (value is String && value.isNotEmpty) {
            return StandardSuccess(value);
          }

          return const StandardFailure([
            StandardIssue(message: 'Expected a non-empty string'),
          ]);
        },
        jsonSchema: StandardJsonSchemaConverter(
          input: (options) {
            if (options.target != JsonSchemaTarget.draft07) {
              throw UnsupportedError('Only Draft-7 is supported.');
            }

            return {'type': 'string'};
          },
          output: (options) => {'type': 'string'},
        ),
      );
}