dart-lang

Rules and formatting guidelines for writing Dart /// API documentation and doc comments. Use when documenting Dart code, writing doc comments for any Dart declaration (libraries, classes, methods, variables, etc.), or when instructed to follow the Effective Dart documentation guidelines.

Help users write syntactically and semantically correct primary constructors in Dart, and migrate/use the new constructor syntax, empty-body semicolon syntax, in-body initializer list syntax, and abbreviated concise constructor syntax.

Applies Dart 3 pattern matching, switch expressions, and destructuring idiomatically to validate data schemas, handle algebraic data types, and decompose control flow. Use when refactoring complex if-else chains, parsing polymorphic JSON or API responses, destructuring Lists, URI/path segments, String.split() tokens, Records, or Maps, or enforcing exhaustiveness on sealed classes. Don't use for simple boolean conditions, single-variable type promotion (use `is`), or basic collection filtering.

Cross-platform file and directory path manipulation, segment splitting, extension extraction, and context conversion using `package:path` and `package:file`. Use when writing, inspecting, joining, splitting, or refactoring file paths, directory names, or extensions, or replacing raw string path operations (`.split('/')`, `'$dir/$file'`, `.endsWith('.ext')`, `.replaceAll('\\', '/')`). Don't use for HTTP network URI routing, database query strings, or non-path string processing.

Guide agents to use `package:ffigen` to automatically generate FFI bindings instead of writing them manually. Use this skill when a task involves writing new FFI bindings, extending C/Objective-C/Swift integrations, or replacing hand-crafted `dart:ffi` setups.

How to inject external code examples into Dartdoc using the {@example} directive, and how to filter those files using #hide, #region, and #endregion tags.

Guides agents in compiling and packaging C/C++ source code into dynamic or static libraries (Code Assets) using Dart's Native Assets hook system (via hook/build.dart and hook/link.dart utilizing package:hooks and package:native_toolchain_c). Use when a user asks to: 'setup native assets', 'compile C/C++ source code', 'bundle dynamic libraries', 'build native C code', 'link native assets', 'implement build.dart or link.dart hooks', or 'integrate C/C++ interop in Dart/Flutter'. Helps agents avoid manual toolchain orchestration and configures secure hash-validated binary downloads or advanced linker tree-shaking with package:record_use mapping.

Execute `dart analyze` to identify warnings and errors, and use `dart fix --apply` to automatically resolve mechanical lint issues. Use during development to ensure code quality and before committing changes.

Workflow for fixing package version conflicts. Use this when `pub get` fails due to incompatible package versions.

Replace the usage of `expect` and similar functions from `package:matcher` to `package:checks` equivalents.

Define and generate mock objects for external dependencies using `package:mockito` and `build_runner`. Use when unit testing classes that depend on complex external services like APIs or databases.

Uses get_runtime_errors and lsp to fetch an active stack trace, locate the failing line, apply a fix, and verify resolution via hot_reload.

Collect coverage using the coverage packge and create an LCOV report

Architectural patterns, entrypoint structure, exit codes, stream routing, and subprocess spawning for Dart command-line interface (CLI) applications. Use when building CLI tools, console utilities, scripts, argument parsing with `package:args` (ArgParser or CommandRunner), handling exit codes, configuring executables in pubspec.yaml, spawning Dart subprocesses, or compiling native CLI binaries. Don't use for Flutter UI widgets, web applications, or standalone HTTP backend servers.

Write and organize unit tests for functions, methods, and classes using `package:test`. Use when creating new logic or fixing bugs to ensure code remains correct and regression-free.