Important notice:Moor has been renamed to Drift. Learn more here.

Builder options

Advanced options applied when writing the generated code

The drift_dev package supports a range of options that control how code is generated. In most cases, the default settings should be sufficient. But if you want to try out new features faster or configure how drift-generated code looks like, you can use the available options listed below. You can also see the section on recommended options for advice on which options to use.

To use the options, create a build.yaml file in the root of your project (e.g. next to your pubspec.yaml):

# build.yaml. This file is quite powerful, see

          compact_query_methods: true

Available options

At the moment, drift supports these options:

  • write_from_json_string_constructor: boolean. Adds a .fromJsonString factory constructor to generated data classes. By default, we only write a .fromJson constructor that takes a Map<String, dynamic>.
  • override_hash_and_equals_in_result_sets: boolean. When drift generates another class to hold the result of generated select queries, this flag controls whether drift should override operator == and hashCode in those classes. In recent versions, it will also override toString if this option is enabled.
  • compact_query_methods (defaults to true): For queries declared on a @DriftDatabase or @DriftAccessor annotation, drift used to generate three methods: A base method returning a Selectable and then two helper methods returning a Stream or a Future. As the Selectable class contains its own methods to convert it to a Stream and Future, the two later methods only exist for backwards compatibility. When this flag is enabled, drift won't write them at all. This flag is enabled by default in moor 3.0 and drift, but it can still be disabled.
  • skip_verification_code: Generated tables contain a significant chunk of code to verify integrity of inserted data and report detailed errors when the integrity is violated. If you're only using inserts with SQL, or don't need this functionality, enabling this flag can help to reduce the amount generated code.
  • use_data_class_name_for_companions: By default, the name for companion classes is based on the table name (e.g. a @DataClassName('Users') class UsersTable extends Table would generate a UsersTableCompanion). With this option, the name is based on the data class (so UsersCompanion in this case).
  • use_column_name_as_json_key_when_defined_in_moor_file (defaults to true): When serializing columns declared inside a .moor (or .drift) file from and to json, use their sql name instead of the generated Dart getter name (so a column named user_name would also use user_name as a json key instead of userName). You can always override the json key by using a JSON KEY column constraint (e.g. user_name VARCHAR NOT NULL JSON KEY userName).
  • generate_connect_constructor: Generate necessary code to support the isolate runtime. This is a build option because isolates are still experimental. This will be the default option eventually.
  • eagerly_load_dart_ast: Drift's builder will load the resolved AST whenever it encounters a Dart file, instead of lazily when it reads a table. This is used to investigate rare builder crashes.
  • data_class_to_companions (defaults to true): Controls whether drift will write the toCompanion method in generated data classes.
  • mutable_classes (defaults to false): The fields generated in generated data, companion and result set classes are final by default. You can make them mutable by setting mutable_classes: true.
  • raw_result_set_data: The generator will expose the underlying QueryRow for generated result set classes
  • apply_converters_on_variables: Applies type converters to variables in compiled statements.
  • generate_values_in_copy_with: Generates a Value<T?> instead of T? for nullable columns in copyWith. This allows to set columns back to null (by using Value(null)). Passing null was ignored before, making it impossible to set columns to null.
  • named_parameters: Generates named parameters for named variables in SQL queries.
  • named_parameters_always_required: All named parameters (generated if named_parameters option is true) will be required in Dart.
  • new_sql_code_generation: Generates SQL statements from the parsed AST instead of replacing substrings. This will also remove unnecessary whitespace and comments. If enabling this option breaks your queries, please file an issue!
  • scoped_dart_components: Generates a function parameter for Dart placeholders in SQL. The function has a parameter for each table that is available in the query, making it easier to get aliases right when using Dart placeholders.
  • null_aware_type_converters: Consider the type of applied type converters to determine nullability of columns in Dart.

Assumed SQL environment

You can configure the SQL dialect you want to target with the sql build option. When using sqlite, you can further configure the assumed sqlite3 version and enabled extensions for more accurate analysis.

Note that these options are used for static analysis only and don't have an impact on the actual sqlite version at runtime.

To define the sqlite version to use, set sqlite.version to the major.minor version:

            dialect: sqlite
              version: "3.34"

With that option, the generator will emit warnings when using newer sqlite version. For instance, using more than one upsert clause is not supported in 3.34, so an error would be reported. Currently, the generator can't provide compatibility checks for versions below 3.34, which is the minimum version needed in options.

Available extensions

Note: This enables extensions in the analyzer for custom queries only. For instance, when the json1 extension is enabled, the json functions can be used in drift files. This doesn't necessarily mean that those functions are supported at runtime! Both extensions are available on iOS 11 or later. On Android, they're only available when using a NativeDatabase.

            dialect: sqlite
                - json1
                - fts5
                - moor_ffi

We currently support the following extensions:

  • json1: Support static analysis for json_ functions in moor files
  • fts5: Support CREATE VIRTUAL TABLE statements for fts5 tables and the MATCH operator. Functions like highlight or bm25 are available as well.
  • moor_ffi: Enables support for functions that are only available when using a NativeDatabase. This contains pow, sqrt and a variety of trigonometric functions. Details on those functions are available here.
  • math: Assumes that sqlite3 was compiled with math functions. This module is largely incompatible with the moor_ffi module.

In general, we recommend using the default options. However, some options will be enabled by default in a future drift release. At the moment, they're opt-in to not break existing users. These options are:

  • apply_converters_on_variables
  • generate_values_in_copy_with
  • new_sql_code_generation
  • scoped_dart_components

We recommend enabling these options.

You can disable some default drift features and reduce the amount of generated code with the following options:

  • skip_verification_code: true: You can remove a significant portion of generated code with this option. The downside is that error messages when inserting invalid data will be less specific.
  • data_class_to_companions: false: Don't generate the toCompanion method on data classes. If you don't need that method, you can disable this option.

Using drift classes in other builders

It is possible to use classes generated by drift in other builders. Due to technicalities related to Dart's build system and source_gen, this approach requires a custom configuration and minor code changes. Put this content in a file called build.yaml next to your pubspec.yaml:

    # disable the default generators, we'll only use the non-shared drift generator here
    auto_apply_builders: false
        enabled: true
        # If needed, you can configure the builder like this:
        # options:
        #   skip_verification_code: true
        #   use_experimental_inference: true
      # This builder is necessary for drift-file preprocessing. You can disable it if you're not
      # using .drift files with type converters.
        enabled: true
    dependencies: ['your_package_name']
      # Disable drift builders. By default, those would run on each target
        enabled: false
        enabled: false
      # we don't need to disable drift|not_shared, because it's disabled by default

In all files that use generated drift code, you'll have to replace part 'filename.g.dart' with part 'filename.drift.dart'. If you use drift and another builder in the same file, you'll need both .g.dart and .drift.dart as part-files.

A full example is available as part of the drift repo.

If you run into any problems with this approach, feel free to open an issue on drift.

The technicalities, explained

Almost all code generation packages use a so called "shared part file" approach provided by source_gen. It's a common protocol that allows unrelated builders to write into the same .g.dart file. For this to work, each builder first writes a .part file with its name. For instance, if you used drift and built_value in the same project, those part files could be called .drift.part and .built_value.part. Later, the common source_gen package would merge the part files into a single .g.dart file.

This works great for most use cases, but a downside is that each builder can't see the final .g.dart file, or use any classes or methods defined in it. To fix that, drift offers an optional builder - drift_dev|not_shared - that will generate a separate part file only containing code generated by drift. So most of the work resolves around disabling the default generator of drift and use the non-shared generator instead.

Finally, we need to the build system to run drift first, and all the other builders otherwise. This is why we split the builders up into multiple targets. The first target will only run drift, the second target has a dependency on the first one and will run all the other builders.