Bench: cover Bun's isolated .bun store

Bun 1.3.2+ installs with the isolated linker by default, keeping every
package only in node_modules/.bun/<name>@<version>/node_modules/<name>.
#496 taught the npm crawler (scan, apply's resolver, VEX) to walk that
store, but the suite only had a hoisted Bun layout, so the new walk was
never timed and a regression back to "2700 lockfile-only packages"
would have gone unnoticed.

Add bun-isolated/{hosted,rescan}: the same text bun.lock as bun/*, with
a pnpm-shaped .bun store, per-entry dependency links, Bun's
.bun/node_modules hoist links and root links for direct deps only. A
pre-#496 binary fails it (lockfileOnlyPackages: got 2700, want 0).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: claude

crates/socket-patch-bench/README.md

@@ -35,8 +35,9 @@ Each scenario is one project and one `scan` invocation:
 
 Package managers (`<pm>`), each in its native lockfile format and install
 layout: `npm`, `pnpm` (isolated `.pnpm` store with symlinks), `yarn-classic`,
-`yarn-berry` (node-modules linker), `bun` (text `bun.lock`), `vlt`
-(`.vlt` store), `pip` (hash-pinned `requirements.txt`), `uv`, `pylock`
+`yarn-berry` (node-modules linker), `bun` (text `bun.lock`, hoisted),
+`bun-isolated` (the same lockfile, Bun 1.3's isolated `.bun` store),
+`vlt` (`.vlt` store), `pip` (hash-pinned `requirements.txt`), `uv`, `pylock`
 (PEP 751), `poetry`, `pipenv`, `pdm`, `bundler`, `composer`, `cargo`,
 `golang`, `nuget` and `maven`. Deno has no hosted rewrite and is not
 benchmarked separately.

crates/socket-patch-bench/src/fixtures/mod.rs

@@ -132,6 +132,13 @@ pub static ALL: &[Pm] = &[
         patched: 60,
         build: npm::build_bun,
     },
+    Pm {
+        name: "bun-isolated",
+        description: "bun (text bun.lock v1, isolated node_modules/.bun store)",
+        packages: 3000,
+        patched: 60,
+        build: npm::build_bun_isolated,
+    },
     Pm {
         name: "vlt",
         description: "vlt (vlt-lock.json v1, node_modules/.vlt store)",

crates/socket-patch-bench/src/fixtures/npm.rs

@@ -1,5 +1,5 @@
 //! npm-family projects. One deterministic dependency graph is written out
-//! as each package manager's lockfile and install layout, so the six
+//! as each package manager's lockfile and install layout, so the seven
 //! scenarios differ only in what each package manager puts on disk.
 
 use std::collections::BTreeMap;
@@ -689,6 +689,47 @@ pub fn build_bun(t: &mut Tree, size: Size) -> std::io::Result<Fixture> {
     Ok(fixture(&g, g.patches(false), &["bun.lock"], &[]))
 }
 
+/// Bun's isolated linker (the default since Bun 1.3.2): the same text
+/// `bun.lock`, but every package lives only in the pnpm-shaped store
+/// `node_modules/.bun/<name>@<version>/node_modules/<name>` (scoped
+/// `@scope+leaf@…`), its dependencies linked beside it, the root linking
+/// direct dependencies only, and `.bun/node_modules` holding Bun's hoist
+/// links.
+pub fn build_bun_isolated(t: &mut Tree, size: Size) -> std::io::Result<Fixture> {
+    let g = graph("bun-isolated", size);
+    t.write("project/package.json", g.package_json())?;
+    t.write("project/bun.lock", bun_lock(&g))?;
+    let mut rng = Rng::new("bun-isolated-install");
+    for p in &g.pkgs {
+        let entry = format!("project/node_modules/.bun/{}/node_modules", p.store_key());
+        write_package(t, &format!("{entry}/{}", p.name), p, &mut rng)?;
+        for (d, v) in &p.deps {
+            let Some(dep) = g.resolve(p, d, v) else {
+                continue;
+            };
+            let up = "../".repeat(1 + d.matches('/').count());
+            let target = format!("{up}../{}/node_modules/{d}", dep.store_key());
+            t.symlink(&target, &format!("{entry}/{d}"))?;
+        }
+        if !p.is_nested() {
+            let up = "../".repeat(1 + p.name.matches('/').count());
+            t.symlink(
+                &format!("{up}{}/node_modules/{}", p.store_key(), p.name),
+                &format!("project/node_modules/.bun/node_modules/{}", p.name),
+            )?;
+        }
+    }
+    for p in g.direct() {
+        let up = "../".repeat(p.name.matches('/').count());
+        t.symlink(
+            &format!("{up}.bun/{}/node_modules/{}", p.store_key(), p.name),
+            &format!("project/node_modules/{}", p.name),
+        )?;
+    }
+    t.mkdir("home")?;
+    Ok(fixture(&g, g.patches(false), &["bun.lock"], &[]))
+}
+
 // ── vlt ────────────────────────────────────────────────────────────────
 
 fn vlt_id(p: &Pkg) -> String {