Closes https://github.com/flutter/flutter/issues/162399.
Closes https://github.com/flutter/flutter/issues/163272.
`refreshPluginsList` is commonly called in iOS/macOS apps, more times
than you expect (and load bearing);
https://github.com/flutter/flutter/issues/157391.
With `--explicit-package-dependencies`, we no longer write (or compare)
the output of `.flutter-plugins`. The iOS/macOS workflows required `pod
install` output to be invalidated when plugins when change, but the
logic that was being used to see if plugins changed _only_ worked for
the `.flutter-plugins` file format.
In the original code:
```txt
# oldPluginsFileStringContent
{"info":"This is a generated file; do not edit or check into version control.","plugins":{"ios":[{"name":"integration_test","path":"/Users/matanl/Developer/flutter/packages/integration_test/","native_build":true,"dependencies":[],"dev_dependency":false},{"name":"ios_objc_cocoapods_plugin","path":"/var/folders/qw/qw_3qd1x4kz5w975jhdq4k58007b7h/T/swift_package_manager_enabled.XrEWXS/ios_objc_cocoapods_plugin/","native_build":true,"dependencies":[],"dev_dependency":false}],"android":[{"name":"integration_test","path":"/Users/matanl/Developer/flutter/packages/integration_test/","native_build":true,"dependencies":[],"dev_dependency":false}],"macos":[],"linux":[],"windows":[],"web":[]},"dependencyGraph":[{"name":"integration_test","dependencies":[]},{"name":"ios_objc_cocoapods_plugin","dependencies":[]}],"date_created":"2025-02-13 17:01:11.023097","version":"3.30.0-1.0.pre.163","swift_package_manager_enabled":{"ios":true,"macos":false}}
# pluginsMap
{ios: [{name: integration_test, path: /Users/matanl/Developer/flutter/packages/integration_test/, native_build: true, dependencies: [], dev_dependency: false}, {name: ios_objc_cocoapods_plugin, path: /var/folders/qw/qw_3qd1x4kz5w975jhdq4k58007b7h/T/swift_package_manager_enabled.XrEWXS/ios_objc_cocoapods_plugin/, native_build: true, dependencies: [], dev_dependency: false}], android: [{name: integration_test, path: /Users/matanl/Developer/flutter/packages/integration_test/, native_build: true, dependencies: [], dev_dependency: false}], macos: [], linux: [], windows: [], web: []}
```
As you can see, `pluginsChanged =
oldPluginsFileStringContent.contains(pluginsMap.toString());` was
_always_ `false`, but we never knew because we'd always just fall back
to using the `.flutter-plugins` content comparison (which always
worked).
I added a test as well.
This also appears to fix
https://github.com/flutter/flutter/issues/162399.
/cc @jmagman @jonahwilliams
29d1e10a02