AGENTS.md

1# Agent Guide for the Flutter Packages Repository
2 
3This document provides guidance for AI agents to effectively contribute to the `flutter/packages` repository.
4 
5## Guiding Principles for Contributions
6 
7- **Format All Code**: Every code change must be formatted using the repository's tools.
8- **Pass All Tests**: All changes must pass linting, analysis, and relevant tests.
9- **Update CHANGELOGs**: Any user-facing change or bug fix in a package requires an update to its `CHANGELOG.md` and `pubspec.yaml` version. Ensure you follow the [CHANGELOG style guide](https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#changelog-style).
10- **Follow Conventions**: Adhere to the repository's specific conventions, such as federated plugin structure and code generation steps.
11 
12## Agent Environment Setup
13 
14To ensure a consistent and functional environment, configure your VM with the following setup. This provides the necessary Flutter SDK and dependencies for building and testing packages.
15 
16```bash
17curl -L https://storage.googleapis.com/flutter_infra_release/releases/stable/linux/flutter_linux_3.32.8-stable.tar.xz | tar -xJ -C $HOME
18export FLUTTER_HOME=$HOME/flutter
19export PATH=$FLUTTER_HOME/bin:$PATH
20flutter --disable-analytics
21flutter precache --force
22# Sanity check the configuration.
23flutter doctor --verbose
24```
25 
26## Repository Overview
27 
28This is a monorepo containing many Flutter packages.
29- First-party packages developed entirely by the Flutter team are in `packages/`.
30- Packages that were originally developed by a third party, but are now maintained by the Flutter team are in `third_party/packages/`.
31- The repository tooling is in `script/tool/`.
32 
33Many packages are part of **federated plugins**. A federated plugin has a main package (e.g., `path_provider`) that defines the API used by plugin clients, a platform interface package (e.g., `path_provider_platform_interface`) that defines the interface that each platform implementation must implement, and one or more platform implementation packages (e.g., `path_provider_android`, `path_provider_ios`) that implement that platform interface. When working on a federated plugin, you may need to modify multiple packages.
34 
35For more details, see the main `README.md` and `CONTRIBUTING.md`.
36 
37## Core Tooling and Workflows
38 
39The primary tool for this repository is `flutter_plugin_tools.dart`.
40 
41### Initial Setup
42 
43First, define an environment variable for the repository root directory and initialize the tooling:
44```bash
45# Define an environment variable for the repository root.
46export REPO_ROOT=$(pwd)
47 
48# Verify that the environment variable is working correctly.
49echo "Repository root directory: $REPO_ROOT"
50
51dart pub get -C $REPO_ROOT/script/tool
52```
53 
54### Identifying Target Packages
55 
56Most tool commands take a `--packages` argument. You must correctly identify all packages affected by your changes. You can derive this from git diff.
57 
58For example, to find changed files against the main branch of the upstream remote (assuming the upstream remote is named `origin`):
59 
60```bash
61git diff --name-only origin/main...HEAD
62```
63 
64Then, for each file path, find its enclosing package. A package is a directory containing a `pubspec.yaml` file. The directory name is usually the package name. Ignore `pubspec.yaml` files within `example/` directories when determining the package for a file.
65 
66#### Targeting All Packages
67 
68Running a tool command without a `--packages` argument will run the command on all packages. For example, a dependency can be updated for all packages in the repository:
69 
70```bash
71dart run $REPO_ROOT/script/tool/bin/flutter_plugin_tools.dart update-dependency --pub-package <dependency_name>
72```
73 
74### Common Commands
75 
76- **Formatting**: Always format your changes.
77 
78```bash
79  dart run $REPO_ROOT/script/tool/bin/flutter_plugin_tools.dart format --packages <changed_packages>
80```
81- **Testing**: All changes must pass analysis and tests:
82 
83```bash
84  # Run static analysis
85  dart run $REPO_ROOT/script/tool/bin/flutter_plugin_tools.dart analyze --packages <changed_packages>
86  # Run Dart unit tests
87  dart run $REPO_ROOT/script/tool/bin/flutter_plugin_tools.dart dart-test --packages <changed_packages>
88```
89 
90  The tool can also run native and integration tests, but these may require a more complete environment than is available.
91- **Validation**: Run these checks to ensure that changes follow team guidelines:
92```bash
93  dart run $REPO_ROOT/script/tool/bin/flutter_plugin_tools.dart validate --packages <changed_packages>
94  dart run $REPO_ROOT/script/tool/bin/flutter_plugin_tools.dart publish-check --packages <changed_packages>
95  dart run $REPO_ROOT/script/tool/bin/flutter_plugin_tools.dart license-check
96```
97 
98### Specialized Workflows
99 
100- **Federated Plugin Development**: If you change multiple packages in a federated plugin that depend on each other, use `make-deps-path-based` to make their pubspec.yaml files use `path:` dependencies. This allows you to test them together locally.
101```bash
102  dart run $REPO_ROOT/script/tool/bin/flutter_plugin_tools.dart make-deps-path-based --target-dependencies=<changed_plugin_packages>
103```
104 
105  The CI system will run tests with path-based dependencies automatically, so this is not required for PRs, but can be useful for local testing.
106- **Updating Dependencies**: To update a dependency across multiple packages:
107```bash
108  dart run $REPO_ROOT/script/tool/bin/flutter_plugin_tools.dart update-dependency --pub-package <dependency_name> --packages <packages_to_update>
109```
110- **Updating README Code Samples**: If you change example code that is included in a README.md:
111```bash
112  dart run $REPO_ROOT/script/tool/bin/flutter_plugin_tools.dart update-excerpts --packages <changed_packages>
113```
114 
115## Code Generators
116 
117Some packages use code generators, and changes to those packages require running the relevant code generators.
118 
119- **Pigeon**: If you change a file in a `pigeons/` directory, you must run the Pigeon generator:
120```bash
121  # Run from the package's directory
122  dart run pigeon --input pigeons/<changed_file>.dart
123```
124- **Mockito**: If you change code in a package that uses `mockito` for tests (check `dev_dependencies` in `pubspec.yaml`), you must run its mock generator:
125```bash
126  # Run from the package's directory
127  dart run build_runner build -d
128```
129 
130## Code Style
131 
132All code must adhere to the repository's style guides. The `format` command handles most of this, but be aware of the specific style guides for each language, as detailed in [CONTRIBUTING.md](./CONTRIBUTING.md#style):
133- **Dart**: Flutter style, formatted with `dart format`.
134- **C++**: Google style, formatted with `clang-format`.
135- **Java**: Google style, formatted with `google-java-format`.
136- **Kotlin**: Android Kotlin style, formatted with `ktfmt`.
137- **Objective-C**: Google style, formatted with `clang-format`.
138- **Swift**: Google style, formatted with `swift-format`.
139- **Comments**: Avoid adding redundant or trivial comments that simply restate what the code itself does (e.g., repeating method calls in English). Comments should explain the *why* behind complex or non-obvious logic, or serve as public API documentation.
140 
141## Version and CHANGELOG updates
142 
143Any PR that changes non-test code in a package should update its version in pubspec.yaml and add a corresponding entry in CHANGELOG.md.
144 
145**This process can be automated**. The `update-release-info` command is the preferred way to handle this. It determines changed packages, bumps versions, and updates changelogs automatically.
146```bash
147dart run $REPO_ROOT/script/tool/bin/flutter_plugin_tools.dart update-release-info \
148  --version=minimal \
149  --base-branch=origin/main \
150  --changelog="A description of the changes."
151```
152 
153- `--version=minimal`: Bumps patch for bug fixes, and skips unchanged packages. This is usually the best option unless a new feature is being added.
154  - When making public API changes, use `--version=minor` instead.
155- `--base-branch=origin/main`: Diffs against the `main` branch to find changed packages.
156 
157If you update manually, follow semantic versioning and the [repository's CHANGELOG style](https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#changelog-style).
158