Dart Best Practices

---
name: dart-best-practices
description: 'Dart code quality conventions: naming, const/final/var hierarchy, single quotes, trailing commas, collection idioms, tear-offs, and import organization. Use when writing new Dart code or reviewing for style violations — wrong import style, global variables, var misuse, anonymous lambdas where tear-offs fit, or missing trailing commas.'
metadata:
  triggers:
    files:
    - '**/*.dart'
    keywords:
    - naming
    - convention
    - trailing comma
    - import
    - tear-off
---
# Dart Best Practices

## **Priority: P1 (OPERATIONAL)**


- **Scoping**:
 - No global variables.
 - Private globals (if required) must start with `_`.
- **Immutability**: Use `const` > `final` > `var`.
- **Config**: Use `--dart-define` for secrets. Never hardcode API keys.
- **Naming**: Follow [effective-dart](https://dart.dev/guides/language/effective-dart) (PascalCase classes, camelCase members).
- **Strings**: Prefer single quotes; use double quotes only for interpolation needs.
- **Trailing Commas**: Always use trailing commas for multi-line literals/params.
- **Expression Bodies**: Prefer `=>` for single-expression functions/getters.
- **Collections**:
 - Use `.map`, `.where`, `.fold`, `.any` over manual loops when clarity improves.
 - Type empty collections (`<String>[]`, `<String, User>{}`) to avoid `dynamic`.
 - Use collection `if`/`for` and spread operators for composable lists/maps.
- **Async**: Always `await` futures unless intentionally fire-and-forget.

```dart
import 'models/user.dart'; // Good
import 'package:app/models/user.dart'; // Avoid local absolute
```

### Anti-Patterns

- **No var for non-obvious types**: Use `final` or explicit type; `var` only for locally-obvious short scopes.
- **No package imports within same package**: Use relative imports for intra-package files.
- **No top-level mutable state**: Encapsulate in class or inject via DI.
- **No anonymous lambdas for tear-offs**: Prefer `list.forEach(doSomething)` over anonymous form.