This PR adds initial support for Swift Package Manager (SPM). Users must opt in. Only compatible with Xcode 15+.
Fixes https://github.com/flutter/flutter/issues/146369.
## Included Features
This PR includes the following features:
* Enabling SPM via config
`flutter config --enable-swift-package-manager`
* Disabling SPM via config (will disable for all projects)
`flutter config --no-enable-swift-package-manager`
* Disabling SPM via pubspec.yaml (will disable for the specific project)
```
flutter:
disable-swift-package-manager: true
```
* Migrating existing apps to add SPM integration if using a Flutter plugin with a Package.swift
* Generates a Swift Package (named `FlutterGeneratedPluginSwiftPackage`) that handles Flutter SPM-compatible plugin dependencies. Generated package is added to the Xcode project.
* Error parsing of common errors that may occur due to using CocoaPods and Swift Package Manager together
* Tool will print warnings when using all Swift Package plugins and encourage you to remove CocoaPods
This PR also converts `integration_test` and `integration_test_macos` plugins to be both Swift Packages and CocoaPod Pods.
## How it Works
The Flutter CLI will generate a Swift Package called `FlutterGeneratedPluginSwiftPackage`, which will have local dependencies on all Swift Package compatible Flutter plugins.
The `FlutterGeneratedPluginSwiftPackage` package will be added to the Xcode project via altering of the `project.pbxproj`.
In addition, a "Pre-action" script will be added via altering of the `Runner.xcscheme`. This script will invoke the flutter tool to copy the Flutter/FlutterMacOS framework to the `BUILT_PRODUCTS_DIR` directory before the build starts. This is needed because plugins need to be linked to the Flutter framework and fortunately Swift Package Manager automatically uses `BUILT_PRODUCTS_DIR` as a framework search path.
CocoaPods will continue to run and be used to support non-Swift Package compatible Flutter plugins.
## Not Included Features
It does not include the following (will be added in future PRs):
* Create plugin template
* Create app template
* Add-to-App integration
Fixes https://github.com/flutter/flutter/issues/130277
This PR does two things:
1. introduce a hidden `flutter build _preview` command, that will build a debug windows desktop app and copy it into the SDK's binary cache. This command is only intended to be run during packaging.
2. introduce a new device type, called `PreviewDevice`, which relies on the prebuilt desktop debug app from step 1, copies it into the target app's assets build folder, and then hot reloads their dart code into it.
Support for FFI calls with `@Native external` functions through Native assets on MacOS and iOS. This enables bundling native code without any build-system boilerplate code.
For more info see:
* https://github.com/flutter/flutter/issues/129757
### Implementation details for MacOS and iOS.
Dylibs are bundled by (1) making them fat binaries if multiple architectures are targeted, (2) code signing these, and (3) copying them to the frameworks folder. These steps are done manual rather than via CocoaPods. CocoaPods would have done the same steps, but (a) needs the dylibs to be there before the `xcodebuild` invocation (we could trick it, by having a minimal dylib in the place and replace it during the build process, that works), and (b) can't deal with having no dylibs to be bundled (we'd have to bundle a dummy dylib or include some dummy C code in the build file).
The dylibs are build as a new target inside flutter assemble, as that is the moment we know what build-mode and architecture to target.
The mapping from asset id to dylib-path is passed in to every kernel compilation path. The interesting case is hot-restart where the initial kernel file is compiled by the "inner" flutter assemble, while after hot restart the "outer" flutter run compiled kernel file is pushed to the device. Both kernel files need to contain the mapping. The "inner" flutter assemble gets its mapping from the NativeAssets target which builds the native assets. The "outer" flutter run get its mapping from a dry-run invocation. Since this hot restart can be used for multiple target devices (`flutter run -d all`) it contains the mapping for all known targets.
### Example vs template
The PR includes a new template that uses the new native assets in a package and has an app importing that. Separate discussion in: https://github.com/flutter/flutter/issues/131209.
### Tests
This PR adds new tests to cover the various use cases.
* dev/devicelab/bin/tasks/native_assets_ios.dart
* Runs an example app with native assets in all build modes, doing hot reload and hot restart in debug mode.
* dev/devicelab/bin/tasks/native_assets_ios_simulator.dart
* Runs an example app with native assets, doing hot reload and hot restart.
* packages/flutter_tools/test/integration.shard/native_assets_test.dart
* Runs (incl hot reload/hot restart), builds, builds frameworks for iOS, MacOS and flutter-tester.
* packages/flutter_tools/test/general.shard/build_system/targets/native_assets_test.dart
* Unit tests the new Target in the backend.
* packages/flutter_tools/test/general.shard/ios/native_assets_test.dart
* packages/flutter_tools/test/general.shard/macos/native_assets_test.dart
* Unit tests the native assets being packaged on a iOS/MacOS build.
It also extends various existing tests:
* dev/devicelab/bin/tasks/module_test_ios.dart
* Exercises the add2app scenario.
* packages/flutter_tools/test/general.shard/features_test.dart
* Unit test the new feature flag.
