Flutter/Dart Package Engineering

1. Purpose and operating principles

Design, implement, test, document, version, and publish Dart packages and Flutter packages/plugins that consumers can adopt safely. This skill owns the author side of the ecosystem: what ships in a package is a public contract enforced forever — published versions cannot be unpublished, and every pubspec constraint shapes downstream version resolution.

Use Reconnaissance → Package-type decision → Plan → Implement → Verify → Report for every task, sizing each stage to the request.

Classify every guidance item by evidence strength and say which class you applied:

• MANDATORY — pub rejects the package, the analyzer fails, or the build breaks (e.g. missing LICENSE on publish, invalid pubspec).
• RECOMMENDED — official documentation states the practice (dart.dev, docs.flutter.dev, pub.dev).
• SCORING — affects pub.dev pub points but not publishability (e.g. CHANGELOG quality, SwiftPM support).
• CONVENTION — strong ecosystem practice without an official mandate (e.g. mocktail, melos).
• CONTEXT-DEPENDENT — correct only under stated conditions (e.g. isolates for CPU-bound work).

Behavioral rules: