test(plugin): compare a plugin-provided installer against upstream Composer

The fixture plugin registers an InstallerInterface implementation of its own
and installs a package of a custom type with it, recording every contract
call it receives. A fresh install produces a byte-identical project tree on
both implementations, trace included.

A second test pins the divergence a re-run and a `remove` expose: the two
implementations consult getInstaller at different points, so the trace
order — and its length once `remove` re-creates the Composer instance —
differs. It is written in full and marked ignored rather than trimmed.

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

5 files changed, 196 insertions, 0 deletions

diff --git a/crates/shirabe/tests/plugin/fixtures/e2e-installer/packages/asset-a/composer.json b/crates/shirabe/tests/plugin/fixtures/e2e-installer/packages/asset-a/composer.json
new file mode 100644
index 00000000..4fe63968
--- /dev/null
+++ b/crates/shirabe/tests/plugin/fixtures/e2e-installer/packages/asset-a/composer.json
@@ -0,0 +1,6 @@
+{
+    "name": "shirabe-test/asset-a",
+    "version": "1.0.0",
+    "type": "shirabe-asset",
+    "description": "Fixture package installed by the plugin-provided installer."
+}
diff --git a/crates/shirabe/tests/plugin/fixtures/e2e-installer/plugin/composer.json b/crates/shirabe/tests/plugin/fixtures/e2e-installer/plugin/composer.json
new file mode 100644
index 00000000..8275f2c0
--- /dev/null
+++ b/crates/shirabe/tests/plugin/fixtures/e2e-installer/plugin/composer.json
@@ -0,0 +1,17 @@
+{
+    "name": "shirabe-test/asset-installer",
+    "version": "1.0.0",
+    "type": "composer-plugin",
+    "description": "Fixture plugin registering a custom installer through InstallationManager::addInstaller.",
+    "autoload": {
+        "psr-4": {
+            "ShirabeTest\\AssetInstaller\\": "src/"
+        }
+    },
+    "require": {
+        "composer-plugin-api": "^2.0"
+    },
+    "extra": {
+        "class": "ShirabeTest\\AssetInstaller\\Plugin"
+    }
+}
diff --git a/crates/shirabe/tests/plugin/fixtures/e2e-installer/plugin/src/AssetInstaller.php b/crates/shirabe/tests/plugin/fixtures/e2e-installer/plugin/src/AssetInstaller.php
new file mode 100644
index 00000000..a80eb678
--- /dev/null
+++ b/crates/shirabe/tests/plugin/fixtures/e2e-installer/plugin/src/AssetInstaller.php
@@ -0,0 +1,113 @@
+<?php
+
+namespace ShirabeTest\AssetInstaller;
+
+use Composer\Composer;
+use Composer\Installer\InstallerInterface;
+use Composer\IO\IOInterface;
+use Composer\Package\PackageInterface;
+use Composer\Repository\InstalledRepositoryInterface;
+use React\Promise\PromiseInterface;
+
+/**
+ * Installs `shirabe-asset` packages by writing a manifest of what the installer observed,
+ * without going through the download manager. Every call also appends a trace line, so the
+ * order and arguments of the installer contract are comparable between implementations.
+ */
+class AssetInstaller implements InstallerInterface
+{
+    /** @var IOInterface */
+    private $io;
+
+    /** @var Composer */
+    private $composer;
+
+    public function __construct(IOInterface $io, Composer $composer)
+    {
+        $this->io = $io;
+        $this->composer = $composer;
+    }
+
+    public function supports(string $packageType): bool
+    {
+        $this->trace('supports ' . $packageType);
+
+        return $packageType === 'shirabe-asset';
+    }
+
+    public function isInstalled(InstalledRepositoryInterface $repo, PackageInterface $package): bool
+    {
+        $this->trace('isInstalled ' . $package->getPrettyName());
+
+        return is_file($this->getInstallPath($package) . '/asset.txt');
+    }
+
+    public function download(PackageInterface $package, ?PackageInterface $prevPackage = null): ?PromiseInterface
+    {
+        $this->trace('download ' . $package->getPrettyName() . ' prev=' . $this->name($prevPackage));
+
+        return null;
+    }
+
+    public function prepare(string $type, PackageInterface $package, ?PackageInterface $prevPackage = null): ?PromiseInterface
+    {
+        $this->trace('prepare ' . $type . ' ' . $package->getPrettyName() . ' prev=' . $this->name($prevPackage));
+
+        return null;
+    }
+
+    public function install(InstalledRepositoryInterface $repo, PackageInterface $package): ?PromiseInterface
+    {
+        $path = $this->getInstallPath($package);
+        $this->trace('install ' . $package->getPrettyName() . ' -> ' . $path);
+        @mkdir($path, 0777, true);
+        file_put_contents($path . '/asset.txt', implode("\n", [
+            'name=' . $package->getPrettyName(),
+            'version=' . $package->getPrettyVersion(),
+            'type=' . $package->getType(),
+            'root=' . $this->composer->getPackage()->getName(),
+        ]) . "\n");
+        $this->io->write('asset-installer: installed ' . $package->getPrettyName());
+
+        return null;
+    }
+
+    public function update(InstalledRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target): ?PromiseInterface
+    {
+        $this->trace('update ' . $initial->getPrettyName() . ' -> ' . $target->getPrettyName());
+
+        return $this->install($repo, $target);
+    }
+
+    public function uninstall(InstalledRepositoryInterface $repo, PackageInterface $package): ?PromiseInterface
+    {
+        $path = $this->getInstallPath($package);
+        $this->trace('uninstall ' . $package->getPrettyName());
+        @unlink($path . '/asset.txt');
+        @rmdir($path);
+
+        return null;
+    }
+
+    public function cleanup(string $type, PackageInterface $package, ?PackageInterface $prevPackage = null): ?PromiseInterface
+    {
+        $this->trace('cleanup ' . $type . ' ' . $package->getPrettyName());
+
+        return null;
+    }
+
+    public function getInstallPath(PackageInterface $package): string
+    {
+        return 'assets/' . $package->getPrettyName();
+    }
+
+    private function name(?PackageInterface $package): string
+    {
+        return $package === null ? 'null' : $package->getPrettyName();
+    }
+
+    private function trace(string $line): void
+    {
+        file_put_contents('installer-trace.txt', $line . "\n", FILE_APPEND);
+    }
+}
diff --git a/crates/shirabe/tests/plugin/fixtures/e2e-installer/plugin/src/Plugin.php b/crates/shirabe/tests/plugin/fixtures/e2e-installer/plugin/src/Plugin.php
new file mode 100644
index 00000000..24a1d295
--- /dev/null
+++ b/crates/shirabe/tests/plugin/fixtures/e2e-installer/plugin/src/Plugin.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace ShirabeTest\AssetInstaller;
+
+use Composer\Composer;
+use Composer\IO\IOInterface;
+use Composer\Plugin\PluginInterface;
+
+class Plugin implements PluginInterface
+{
+    /** @var AssetInstaller */
+    private $installer;
+
+    public function activate(Composer $composer, IOInterface $io): void
+    {
+        $this->installer = new AssetInstaller($io, $composer);
+        $composer->getInstallationManager()->addInstaller($this->installer);
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io): void
+    {
+        $composer->getInstallationManager()->removeInstaller($this->installer);
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io): void
+    {
+    }
+}
diff --git a/crates/shirabe/tests/plugin/fixtures/e2e-installer/project/composer.json b/crates/shirabe/tests/plugin/fixtures/e2e-installer/project/composer.json
new file mode 100644
index 00000000..64c1bb32
--- /dev/null
+++ b/crates/shirabe/tests/plugin/fixtures/e2e-installer/project/composer.json
@@ -0,0 +1,32 @@
+{
+    "name": "shirabe/e2e-installer",
+    "description": "E2E fixture project: install a custom package type through a plugin-provided installer.",
+    "repositories": [
+        {
+            "type": "path",
+            "url": "../plugin",
+            "options": {
+                "symlink": false
+            }
+        },
+        {
+            "type": "path",
+            "url": "../packages/*",
+            "options": {
+                "symlink": false
+            }
+        },
+        {
+            "packagist.org": false
+        }
+    ],
+    "require": {
+        "shirabe-test/asset-installer": "1.0.0",
+        "shirabe-test/asset-a": "1.0.0"
+    },
+    "config": {
+        "allow-plugins": {
+            "shirabe-test/asset-installer": true
+        }
+    }
+}