remote_config_codegen 0.1.0

Generate typed Dart Remote Config clients and JSON models from a JSON manifest.

Remote Config Codegen

remote_config_codegen is a Dart CLI that generates a type-safe Firebase Remote Config access API and Dart JSON models from a JSON Manifest. It lets Flutter applications read Firebase Remote Config values through typed methods instead of string keys, Firebase getter selection, and manual JSON parsing.

What it generates

Define Firebase Remote Config parameters and JSON value shapes once in a JSON Manifest:

{
  "parameters": {
    "app_new_purchase_flow": {
      "valueType": "BOOLEAN",
      "defaultValue": false
    },
    "app_home_banner_config": {
      "valueType": "JSON",
      "defaultValue": { "banners": [] },
      "valueSchema": { "$ref": "#/$defs/HomeBannerConfig" }
    }
  },
  "$defs": {
    "HomeBannerConfig": {
      "type": "object",
      "required": ["banners"],
      "properties": {
        "banners": { "type": "array", "items": { "type": "string" } }
      }
    }
  }
}

The CLI then generates a Firebase-backed, typed API. With the default json_serializable serializer, the relevant output is equivalent to:

// remote_config_models.dart
@JsonSerializable()
class HomeBannerConfig {
  const HomeBannerConfig({required this.banners});

  factory HomeBannerConfig.fromJson(Map<String, dynamic> json) =>
      _$HomeBannerConfigFromJson(json);

  Map<String, dynamic> toJson() => _$HomeBannerConfigToJson(this);

  final List<String> banners;
}

// remote_config_client.dart
class RemoteConfigClient {
  const RemoteConfigClient(this._remoteConfig);

  final FirebaseRemoteConfig _remoteConfig;

  bool getAppNewPurchaseFlow() =>
      _remoteConfig.getBool('app_new_purchase_flow');

  HomeBannerConfig getAppHomeBannerConfig() {
    try {
      final decoded = jsonDecode(
        _remoteConfig.getString('app_home_banner_config'),
      );
      if (decoded is! Map<String, dynamic>) {
        throw const FormatException('Expected a JSON object.');
      }
      return HomeBannerConfig.fromJson(decoded);
    } on Object {
      return HomeBannerConfig.fromJson(
        <String, dynamic>{'banners': <dynamic>[]},
      );
    }
  }
}

Application code calls typed methods instead of using string keys, Firebase getter selection, or JSON parsing directly:

final client = RemoteConfigClient(FirebaseRemoteConfig.instance);
final bool enabled = client.getAppNewPurchaseFlow();
final HomeBannerConfig banners = client.getAppHomeBannerConfig();

Usage

Place remote_config_codegen.yaml at the root of your Flutter project and run the CLI with the Manifest path.

dart run remote_config_codegen \
  --config config.json

Unless --settings is specified, the CLI reads remote_config_codegen.yaml from the current working directory.

Generation settings

# remote_config_codegen.yaml
dart:
  output_directory: lib/src/generated/remote_config
  serializer: json_serializable
  remote_config_client_class_name: RemoteConfigClient

serializer supports json_serializable and freezed, and defaults to json_serializable when omitted. If remote_config_client_class_name is omitted, it defaults to RemoteConfigClient.

The generated code is Firebase-specific in the first release. The generated RemoteConfigClient receives FirebaseRemoteConfig directly through its constructor, so the consuming application needs firebase_remote_config.

Generated JSON models require these pinned packages in the consuming application:

dependencies:
  json_annotation: 4.12.0

dev_dependencies:
  build_runner: 2.15.1
  json_serializable: 6.14.0

To generate Freezed models, set serializer: freezed and use these pinned packages instead:

dependencies:
  freezed_annotation: 3.1.0
  json_annotation: 4.12.0

dev_dependencies:
  build_runner: 2.15.1
  freezed: 3.2.5
  json_serializable: 6.14.0

After running this CLI, generate the *.g.dart files from the consuming project:

dart run build_runner build

For the initial JSON Schema subset, properties that are not defined by the Schema are ignored by generated models. Remote Config value types are aligned with Firebase: STRING, BOOLEAN, NUMBER, and JSON. Within a JSON value schema, both optional properties and nullable properties are generated as nullable Dart fields (T?).

Every NUMBER parameter generates two methods: get<Parameter>Int() and get<Parameter>Double(). If a JSON parameter cannot be parsed or converted into its model, the generated client falls back to the Manifest's defaultValue.

Every generated Dart file starts with // GENERATED CODE - DO NOT MODIFY BY HAND. Change the Manifest or JSON Schema and run the generator again instead of editing generated files.

Manifest example

{
  "$schema": "./schema/remote_config_manifest.schema.json",
  "parameters": {
    "app_new_purchase_flow": {
      "valueType": "BOOLEAN",
      "defaultValue": false
    },
    "app_home_banner_config": {
      "valueType": "JSON",
      "defaultValue": { "banners": [] },
      "valueSchema": { "$ref": "#/$defs/HomeBannerConfig" }
    }
  },
  "$defs": {
    "HomeBannerConfig": {
      "type": "object",
      "required": ["banners"],
      "properties": {
        "banners": { "type": "array", "items": { "type": "string" } }
      }
    }
  }
}

The package provides the Meta Schema at schema/remote_config_manifest.schema.json. Consumer projects can refer to a copy of this file through $schema. A versioned URL will be provided when the package is published.