feat(plugin): cross alias packages over RPC as proxy stubs

AliasPackage, CompleteAliasPackage and RootAliasPackage now have generated
proxy stubs, so a package handed to a plugin no longer has to be a real
package: it crosses as the stub matching its concrete variant, answers
getAliasOf / setRootPackageAlias / isRootPackageAlias /
hasSelfVersionRequires, and can be constructed from plugin code.

The setters RootPackageInterface declares are routed through that interface
for every root package instead of through the base Package state. Only the
alias variant needs it -- RootAliasPackage overrides all nine to write
through to the package it aliases -- but a real RootPackage delegates to the
same base state either way, so both take one path.

An alias of an alias has no representation here, so narrowing the
constructor argument to a real package is an explicit error rather than a
silent demotion.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

4 files changed, 165 insertions, 0 deletions

diff --git a/crates/shirabe/tests/plugin/alias_package_test.rs b/crates/shirabe/tests/plugin/alias_package_test.rs
new file mode 100644
index 00000000..b32d2b67
--- /dev/null
+++ b/crates/shirabe/tests/plugin/alias_package_test.rs
@@ -0,0 +1,89 @@
+//! Shirabe-specific integration tests for the alias package proxy stubs. Upstream Composer has
+//! no test for this (its plugins run in-process), so the fixture `fixtures/alias-v1` is
+//! Shirabe-owned.
+
+use crate::async_runtime::run;
+use crate::plugin_installer_test::{lock_php_worker, new_installer, php_runtime_available, set_up};
+use shirabe::installer::InstallerInterface;
+use shirabe::package::loader::{ArrayLoader, JsonLoader, JsonLoaderInput};
+use shirabe::package::{
+    CompleteAliasPackageHandle, CompletePackageHandle, PackageInterfaceHandle, RootPackageHandle,
+};
+use shirabe_php_shim::PhpMixed;
+
+fn alias_fixture_package() -> PackageInterfaceHandle {
+    let loader = JsonLoader::new(Box::new(ArrayLoader::new(None, false)));
+    let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
+        .join("tests/plugin/fixtures/alias-v1/composer.json");
+    loader
+        .load(JsonLoaderInput::String(
+            path.canonicalize().unwrap().to_str().unwrap().to_string(),
+        ))
+        .unwrap()
+}
+
+#[test]
+fn test_alias_packages_cross_the_plugin_boundary() {
+    if !php_runtime_available() {
+        return;
+    }
+    let _worker = lock_php_worker();
+    let set_up = set_up();
+
+    let aliased = CompletePackageHandle::new(
+        "vendor/aliased".to_string(),
+        "1.0.0.0".to_string(),
+        "1.0.0".to_string(),
+    );
+    aliased.set_description("an aliased package".to_string());
+    let alias = CompleteAliasPackageHandle::new(
+        aliased.clone(),
+        "2.0.0.0".to_string(),
+        "2.0.0".to_string(),
+    );
+    set_up
+        .repository
+        .borrow_mut()
+        .add_package(alias.clone().into())
+        .unwrap();
+
+    let real_root = RootPackageHandle::new(
+        "dummy/root".to_string(),
+        "1.0.0.0".to_string(),
+        "1.0.0".to_string(),
+    );
+    let root_alias = shirabe::package::RootAliasPackageHandle::new(
+        real_root.clone(),
+        "1.1.0.0".to_string(),
+        "1.1.0".to_string(),
+    );
+    set_up.composer.borrow_mut().set_package(root_alias.into());
+
+    let installer = new_installer(&set_up);
+    set_up.pm.borrow_mut().load_installed_plugins().unwrap();
+    run(installer.install(&set_up.repository, alias_fixture_package())).unwrap();
+
+    assert_eq!(
+        "alias: Composer\\Package\\CompleteAliasPackage vendor/aliased 2.0.0 of Composer\\Package\\CompletePackage 1.0.0\n\
+         alias description: an aliased package\n\
+         alias self-version: no\n\
+         alias root-flag: no\n\
+         alias root-flag: yes\n\
+         root: Composer\\Package\\RootAliasPackage dummy/root 1.1.0 of Composer\\Package\\RootPackage 1.0.0\n\
+         root aliasOf identity: same\n\
+         root minimum stability: stable\n\
+         built: Composer\\Package\\CompleteAliasPackage vendor/aliased 9.9.9 of Composer\\Package\\CompletePackage 1.0.0\n",
+        set_up.io.borrow().get_output()
+    );
+
+    // The flag the plugin set landed on the Rust-side entity, not on a child-side copy.
+    let alias: shirabe::package::AliasPackageHandle = alias.into();
+    assert!(alias.is_root_package_alias());
+
+    // `RootAliasPackage`'s setters write through to the package it aliases.
+    assert_eq!("dev", real_root.get_minimum_stability());
+    assert_eq!(
+        Some(&PhpMixed::String("alias-v1".to_string())),
+        real_root.get_extra().get("seen-by")
+    );
+}
diff --git a/crates/shirabe/tests/plugin/fixtures/alias-v1/Alias/Plugin.php b/crates/shirabe/tests/plugin/fixtures/alias-v1/Alias/Plugin.php
new file mode 100644
index 00000000..373348e8
--- /dev/null
+++ b/crates/shirabe/tests/plugin/fixtures/alias-v1/Alias/Plugin.php
@@ -0,0 +1,63 @@
+<?php
+
+namespace Alias;
+
+use Composer\Composer;
+use Composer\IO\IOInterface;
+use Composer\Package\AliasPackage;
+use Composer\Package\CompleteAliasPackage;
+use Composer\Package\RootAliasPackage;
+use Composer\Plugin\PluginInterface;
+
+class Plugin implements PluginInterface
+{
+    public function activate(Composer $composer, IOInterface $io)
+    {
+        $aliased = null;
+        foreach ($composer->getRepositoryManager()->getLocalRepository()->getPackages() as $package) {
+            if (!$package instanceof AliasPackage) {
+                continue;
+            }
+            $aliased = $package->getAliasOf();
+            $io->write('alias: ' . self::describe($package));
+            $io->write('alias description: ' . $package->getDescription());
+            $io->write('alias self-version: ' . ($package->hasSelfVersionRequires() ? 'yes' : 'no'));
+            $io->write('alias root-flag: ' . ($package->isRootPackageAlias() ? 'yes' : 'no'));
+            $package->setRootPackageAlias(true);
+            $io->write('alias root-flag: ' . ($package->isRootPackageAlias() ? 'yes' : 'no'));
+        }
+
+        $root = $composer->getPackage();
+        if (!$root instanceof RootAliasPackage) {
+            throw new \RuntimeException('not a RootAliasPackage: ' . get_class($root));
+        }
+        $io->write('root: ' . self::describe($root));
+        $io->write('root aliasOf identity: ' . ($root->getAliasOf() === $root->getAliasOf() ? 'same' : 'distinct'));
+        $io->write('root minimum stability: ' . $root->getMinimumStability());
+        $root->setMinimumStability('dev');
+        $root->setExtra(['seen-by' => 'alias-v1']);
+
+        $built = new CompleteAliasPackage($aliased, '9.9.9.9', '9.9.9');
+        $io->write('built: ' . self::describe($built));
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io)
+    {
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io)
+    {
+    }
+
+    private static function describe(AliasPackage $package): string
+    {
+        return sprintf(
+            '%s %s %s of %s %s',
+            get_class($package),
+            $package->getName(),
+            $package->getPrettyVersion(),
+            get_class($package->getAliasOf()),
+            $package->getAliasOf()->getPrettyVersion()
+        );
+    }
+}
diff --git a/crates/shirabe/tests/plugin/fixtures/alias-v1/composer.json b/crates/shirabe/tests/plugin/fixtures/alias-v1/composer.json
new file mode 100644
index 00000000..ac831b6e
--- /dev/null
+++ b/crates/shirabe/tests/plugin/fixtures/alias-v1/composer.json
@@ -0,0 +1,12 @@
+{
+    "name": "alias-v1",
+    "version": "1.0.0",
+    "type": "composer-plugin",
+    "autoload": { "psr-0": { "Alias": "" } },
+    "extra": {
+        "class": "Alias\\Plugin"
+    },
+    "require": {
+        "composer-plugin-api": "^2.0"
+    }
+}
diff --git a/crates/shirabe/tests/plugin/main.rs b/crates/shirabe/tests/plugin/main.rs
index f5a29ba6..7e32a616 100644
--- a/crates/shirabe/tests/plugin/main.rs
+++ b/crates/shirabe/tests/plugin/main.rs
@@ -3,6 +3,7 @@ mod async_runtime;
 #[path = "../common/config_stub.rs"]
 mod config_stub;
 
+mod alias_package_test;
 mod e2e_command_provider_test;
 mod e2e_extension_installer_test;
 mod e2e_installer_test;