refactor(registry): introduce Repository and InstallerExecutor traits

Sets up DI scaffolding for in-process installer E2E tests, mirroring how
Composer's PHPUnit suite swaps Packagist (FactoryMock) and the install
manager (InstallationManagerMock) without touching the network or filesystem.

Additions:
- Repository trait + RepositorySet (Composer's RepositoryInterface analog),
  with PackagistRepository, InlinePackageRepository, VcsRepository impls.
- InstallerExecutor trait (Composer's InstallationManager analog) with
  FilesystemExecutor extracted from install_from_lock.

install_from_lock now delegates per-package install/uninstall verbs to
FilesystemExecutor; console output orchestration stays in the caller so
existing --EXPECT-OUTPUT-shape assertions remain comparable. No behavior
change - all 136 enabled installer fixtures still pass.

Also tightens the installer_fixture\! ignore form to a single token
(installer_fixture\!(name, ignore)) for readability.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

1 files changed, 127 insertions, 0 deletions

diff --git a/crates/mozart-registry/src/repository/mod.rs b/crates/mozart-registry/src/repository/mod.rs
new file mode 100644
index 0000000..1ab8797
--- /dev/null
+++ b/crates/mozart-registry/src/repository/mod.rs
@@ -0,0 +1,127 @@
+//! Repository abstraction over package metadata sources.
+//!
+//! Mirrors Composer's `Composer\Repository\RepositoryInterface::loadPackages`
+//! and `Composer\Repository\RepositoryManager`. The resolver and lockfile
+//! generator query a [`RepositorySet`] instead of calling Packagist directly,
+//! so test code can substitute a set without `PackagistRepository` (mirroring
+//! Composer's `FactoryMock` injecting `repositories: ['packagist' => false]`).
+//!
+//! Concrete implementations live in sibling modules: [`packagist_repo`] for
+//! the live Packagist HTTP repo, [`inline_package_repo`] for `type: package`
+//! entries embedded in `composer.json`, and [`vcs_repo`] for VCS repositories.
+
+use crate::packagist::PackagistVersion;
+
+pub mod inline_package_repo;
+pub mod packagist_repo;
+pub mod vcs_repo;
+
+/// One name-keyed lookup against a repository.
+///
+/// Matches the `$packageNameMap` argument of Composer's `loadPackages`. The
+/// constraint is informational — repositories may use it to skip versions
+/// that obviously can't match (an optimization), but the resolver still
+/// re-checks every returned version when generating rules.
+#[derive(Debug, Clone)]
+pub struct PackageQuery<'a> {
+    pub name: &'a str,
+    /// Raw constraint string from `composer.json`, e.g. `"^1.2"`. `None`
+    /// when the caller wants every version (transitive exploration).
+    pub constraint: Option<&'a str>,
+}
+
+/// Result of a single [`Repository::load_packages`] call.
+///
+/// Mirrors Composer's `['packages' => ..., 'namesFound' => ...]` tuple.
+/// `names_found` lets [`RepositorySet`] short-circuit lower-priority repos
+/// once an upstream repo has authoritatively answered for a name (Composer's
+/// "first repo wins" semantics).
+#[derive(Debug, Default)]
+pub struct LoadResult {
+    pub packages: Vec<NamedPackagistVersion>,
+    pub names_found: Vec<String>,
+}
+
+/// A `PackagistVersion` paired with the canonical package name it answers
+/// for. Inline `type: package` repos can return packages whose own `name`
+/// field differs from the queried name when they declare `replace`/`provide`,
+/// so callers need both.
+#[derive(Debug, Clone)]
+pub struct NamedPackagistVersion {
+    pub name: String,
+    pub version: PackagistVersion,
+}
+
+/// A source of package metadata. Mirrors Composer's `RepositoryInterface`.
+///
+/// Implementations should return an empty [`LoadResult`] (not an error) when
+/// they simply don't know a queried name — [`RepositorySet`] uses that to
+/// fall through to the next repo. Reserve `Err` for genuine I/O failures
+/// the caller cannot route around.
+#[async_trait::async_trait]
+pub trait Repository: Send + Sync {
+    /// Identifier for diagnostics (`"packagist.org"`, `"package"`, `"vcs:<url>"`).
+    fn id(&self) -> &str;
+
+    /// Look up every version of every queried name this repo knows about.
+    async fn load_packages(&self, queries: &[PackageQuery<'_>]) -> anyhow::Result<LoadResult>;
+}
+
+/// Ordered list of repositories. Mirrors `Composer\Repository\RepositoryManager`.
+///
+/// `load_packages` queries each repo in order. Once a repo authoritatively
+/// answers for a name (i.e. lists it in `names_found`), later repos are not
+/// asked about that name — matching Composer's first-repo-wins priority.
+pub struct RepositorySet {
+    repos: Vec<Box<dyn Repository>>,
+}
+
+impl RepositorySet {
+    pub fn new(repos: Vec<Box<dyn Repository>>) -> Self {
+        Self { repos }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.repos.is_empty()
+    }
+
+    pub fn len(&self) -> usize {
+        self.repos.len()
+    }
+
+    /// Iterate over repositories in priority order.
+    pub fn repos(&self) -> impl Iterator<Item = &dyn Repository> {
+        self.repos.iter().map(|b| b.as_ref())
+    }
+
+    /// Query every repo, accumulating packages and tracking which names have
+    /// been authoritatively answered. Names already covered by an earlier
+    /// repo are dropped from the query passed to later repos.
+    pub async fn load_packages(
+        &self,
+        queries: &[PackageQuery<'_>],
+    ) -> anyhow::Result<Vec<NamedPackagistVersion>> {
+        use std::collections::HashSet;
+
+        let mut packages: Vec<NamedPackagistVersion> = Vec::new();
+        let mut answered: HashSet<String> = HashSet::new();
+
+        for repo in &self.repos {
+            let pending: Vec<PackageQuery<'_>> = queries
+                .iter()
+                .filter(|q| !answered.contains(q.name))
+                .cloned()
+                .collect();
+            if pending.is_empty() {
+                break;
+            }
+            let result = repo.load_packages(&pending).await?;
+            for name in result.names_found {
+                answered.insert(name);
+            }
+            packages.extend(result.packages);
+        }
+
+        Ok(packages)
+    }
+}