theme_extensions_gen_annotations

This package defines annotations used with theme_extensions_gen to generate strongly-typed ThemeExtension classes and tooling for Flutter theming.

---

Purpose

Use these annotations to eliminate boilerplate in theme creation. Combined with build_runner and theme_extensions_gen, this package enables:

• Declarative theme structure via @ThemeExtensionTemplate
• Centralized and typed theme values via @ThemeExtensionImpl
• Optional build-time generation of BuildContext extensions

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Annotations

@ThemeExtensionTemplate()

Marks an abstract interface as a template for a ThemeExtension. The generator creates:

• copyWith, lerp, ==, hashCode, and runtimeType
• debugFillProperties if the interface uses Diagnosticable
• A concrete class with a factory constructor and mixin
• A BuildContext extension with getters for all extensions

Example:

@ThemeExtensionTemplate()
abstract interface class ThemedButtonTheme
    extends ThemeExtension<ThemedButtonTheme>
    with _$ThemedButtonThemeMixin, Diagnosticable {
  const factory ThemedButtonTheme({
    required Decoration decoration,
    required TextStyle textStyle,
    required EdgeInsets padding,
  }) = _$ThemedButtonTheme;
}

By default, the generator creates generated/theme_extensions/context_extensions.dart.
This can be customized or disabled via build.yaml:

targets:
  $default:
    builders:
      contextExtensionsGenerator:
        enabled: false

Or with a custom path:

      contextExtensionsGenerator:
        options:
          output_path: "lib/custom/context_extensions.dart"

---

@ThemeExtensionImpl({ String? group })

Marks a list of theme implementations to be combined into a generated list.
Used like this:

@ThemeExtensionImpl()
List<ThemeExtension> get someFeatureThemeExtensions => const [
  ThemedCardTheme(
    // 
  ),
  ThemedButtonTheme(/*...*/),
];

@ThemeExtensionImpl(group: 'dark')
List<ThemeExtension> get someFeatureThemeExtensions => const [
  ThemedCardTheme(/*...*/),
  ThemedButtonTheme(/*...*/),
];

The generator then combines all matching lists into:

• A default file:

  List<ThemeExtension> get themeExtensions => [
    ...someFeatureThemeExtensions,
    ...someAnotherFeatureThemeExtensions,
  ];
  

• A group-specific file (e.g. for "dark"):

  List<ThemeExtension> get themeExtensionsDark => [
    ...someFeatureThemeExtensions,
  ];
  

Configuration in build.yaml:

targets:
  $default:
    builders:
      themeExtensionsImplCombiner:
        options:
          default_output:
            path: "lib/generated/theme_extensions/theme_extensions.dart"
            list_name: "themeExtensions"
          groups:
            dark:
              path: "lib/generated/theme_extensions/theme_extensions_dark.dart"
              list_name: "themeExtensionsDark"