fix(vendor): unpack from local-registry cache path

In rust-lang#15514, Cargo starts direct-extraction from `.crate`
tarball in `$CARGO_HOME/registry/cache` when vendoring. This is fine with
remote registrires but not for local registries, as local registries'
tarball are stored along with index.

This fix abstracts `cache_path` to `RegistryData` trait, so every
registry source type can define its own locationa of tarball cache.

Note that for local-registry when accessing either index or cache, the
assumption is that file lock of the index and cache directory need to
be externally synchronized. Cargo doesn't take care of it.

Author: weihanglo

src/cargo/sources/registry/http_remote.rs

@@ -472,6 +472,10 @@ impl<'gctx> RegistryData for HttpRegistry<'gctx> {
         &self.index_path
     }
 
+    fn cache_path(&self) -> &Filesystem {
+        &self.cache_path
+    }
+
     fn assert_index_locked<'a>(&self, path: &'a Filesystem) -> &'a Path {
         self.gctx
             .assert_package_cache_locked(CacheLockMode::DownloadExclusive, path)

src/cargo/sources/registry/local.rs

@@ -95,6 +95,10 @@ impl<'gctx> RegistryData for LocalRegistry<'gctx> {
         &self.index_path
     }
 
+    fn cache_path(&self) -> &Filesystem {
+        &self.root
+    }
+
     fn assert_index_locked<'a>(&self, path: &'a Filesystem) -> &'a Path {
         // Note that the `*_unlocked` variant is used here since we're not
         // modifying the index and it's required to be externally synchronized.

src/cargo/sources/registry/mod.rs

@@ -248,8 +248,6 @@ pub struct RegistrySource<'gctx> {
     source_id: SourceId,
     /// The path where crate files are extracted (`$CARGO_HOME/registry/src/$REG-HASH`).
     src_path: Filesystem,
-    /// Path to the cache of `.crate` files (`$CARGO_HOME/registry/cache/$REG-HASH`).
-    cache_path: Filesystem,
     /// Local reference to [`GlobalContext`] for convenience.
     gctx: &'gctx GlobalContext,
     /// Abstraction for interfacing to the different registry kinds.
@@ -355,6 +353,12 @@ pub trait RegistryData {
     /// (remote = git, http & local = files).
     fn index_path(&self) -> &Filesystem;
 
+    /// Returns the path of the directory that stores the cache of `.crate` files.
+    ///
+    /// The directory is currently expected to contain a flat list of all `.crate` files,
+    /// named `<package-name>-<version>.crate`.
+    fn cache_path(&self) -> &Filesystem;
+
     /// Loads the JSON for a specific named package from the index.
     ///
     /// * `root` is the root path to the index.
@@ -534,7 +538,6 @@ impl<'gctx> RegistrySource<'gctx> {
         RegistrySource {
             name: name.into(),
             src_path: gctx.registry_source_path().join(name),
-            cache_path: gctx.registry_cache_path().join(name),
             gctx,
             source_id,
             index: index::RegistryIndex::new(source_id, ops.index_path(), gctx),
@@ -665,17 +668,20 @@ impl<'gctx> RegistrySource<'gctx> {
     /// Returns the path to the crate tarball directory,
     /// which is always `<unpack_dir>/<pkg>-<version>`.
     ///
-    /// This holds an assumption that the associated tarball already exists.
+    /// This holds some assumptions
+    ///
+    /// * The associated tarball already exists
+    /// * If this is a local registry,
+    ///   the package cache lock must be externally externally synchronized.
+    ///   Cargo does not take care of it being locked or not.
     pub fn unpack_package_in(
         &self,
         pkg: &PackageId,
         unpack_dir: &Path,
         include: &dyn Fn(&Path) -> bool,
     ) -> CargoResult<PathBuf> {
-        let path = self.cache_path.join(pkg.tarball_name());
-        let path = self
-            .gctx
-            .assert_package_cache_locked(CacheLockMode::DownloadExclusive, &path);
+        let path = self.ops.cache_path().join(pkg.tarball_name());
+        let path = self.ops.assert_index_locked(&path);
         let dst = unpack_dir.join(format!("{}-{}", pkg.name(), pkg.version()));
         let tarball =
             File::open(path).with_context(|| format!("failed to open {}", path.display()))?;

src/cargo/sources/registry/remote.rs

@@ -233,6 +233,10 @@ impl<'gctx> RegistryData for RemoteRegistry<'gctx> {
         &self.index_path
     }
 
+    fn cache_path(&self) -> &Filesystem {
+        &self.cache_path
+    }
+
     fn assert_index_locked<'a>(&self, path: &'a Filesystem) -> &'a Path {
         self.gctx
             .assert_package_cache_locked(CacheLockMode::DownloadExclusive, path)

tests/testsuite/vendor.rs

@@ -2123,7 +2123,6 @@ fn vendor_rename_fallback() {
 
 #[cargo_test]
 fn vendor_local_registry() {
-
     // A regression test for rust-lang/cargo#16412
     let root = paths::root();
     fs::create_dir(root.join(".cargo")).unwrap();
@@ -2137,7 +2136,8 @@ fn vendor_local_registry() {
             [source.my-awesome-local-registry]
             local-registry = 'registry'
         "#,
-    ).unwrap();
+    )
+    .unwrap();
 
     Package::new("bar", "0.0.0")
         .local(true)
@@ -2156,28 +2156,36 @@ fn vendor_local_registry() {
                 bar = "0.0.0"
             "#,
         )
-        .file(
-            "src/lib.rs",
-            "pub fn foo() { bar::bar(); }",
-        )
+        .file("src/lib.rs", "pub fn foo() { bar::bar(); }")
         .build();
 
     p.cargo("vendor --respect-source-config")
-        .with_status(101)
         .with_stderr_data(str![[r#"
 [LOCKING] 1 package to latest compatible version
 [UNPACKING] bar v0.0.0 (registry `[ROOT]/registry`)
    Vendoring bar v0.0.0 ([ROOT]/home/.cargo/registry/src/-[HASH]/bar-0.0.0) to vendor/bar
-[ERROR] failed to sync
-
-Caused by:
-  failed to open [ROOT]/home/.cargo/registry/cache/-[HASH]/bar-0.0.0.crate
+To use vendored sources, add this to your .cargo/config.toml for this project:
 
-Caused by:
-  [NOT_FOUND]
 
 "#]])
         .run();
+
+    assert_e2e().eq(
+        p.read_file("vendor/bar/Cargo.toml"),
+        str![[r#"
+
+            [package]
+            name = "bar"
+            version = "0.0.0"
+            authors = []
+        
+"#]],
+    );
+
+    assert_e2e().eq(
+        p.read_file("vendor/bar/src/lib.rs"),
+        str!["pub fn bar() {}"],
+    );
 }
 
 #[cargo_test]