Fix crawl of --system-site-packages venvs (#409)

crates/socket-patch-cli/src/commands/scan/hosted/python.rs

@@ -63,8 +63,13 @@ pub(super) async fn stale_install_warnings(
             .await
             .unwrap_or_default()
     } else {
-        socket_patch_core::crawlers::python_crawler::find_local_venv_site_packages(&common.cwd)
-            .await
+        let sites =
+            socket_patch_core::crawlers::python_crawler::find_local_venv_site_packages(&common.cwd)
+                .await;
+        // A `--system-site-packages` venv's own copy hides its base
+        // interpreter's (#409).
+        crawler.set_search_order(&sites).await;
+        sites
     };
 
     #[derive(Default)]

crates/socket-patch-cli/src/ecosystem_dispatch.rs

@@ -453,7 +453,7 @@ async fn dispatch_find(
         eco = Ecosystem::Pypi,
         options = options,
         silent = silent,
-        crawler = PythonCrawler,
+        crawler = PythonCrawler::new(),
         get_paths = get_site_packages_paths,
         using_label = "",
         err_label = "Python packages",
@@ -1151,7 +1151,7 @@ async fn crawl_every_ecosystem(
         if walk_pool::fd_limit_is_tight() {
             (
                 crawl!(Ecosystem::Npm, NpmCrawler.crawl_all_with_roots(options)).await,
-                crawl!(Ecosystem::Pypi, PythonCrawler.crawl_all(options)).await,
+                crawl!(Ecosystem::Pypi, PythonCrawler::new().crawl_all(options)).await,
                 crawl!(Ecosystem::Cargo, CargoCrawler.crawl_all(options)).await,
                 crawl!(
                     Ecosystem::Gem,
@@ -1167,7 +1167,7 @@ async fn crawl_every_ecosystem(
         } else {
             tokio::join!(
                 crawl!(Ecosystem::Npm, NpmCrawler.crawl_all_with_roots(options)),
-                crawl!(Ecosystem::Pypi, PythonCrawler.crawl_all(options)),
+                crawl!(Ecosystem::Pypi, PythonCrawler::new().crawl_all(options)),
                 crawl!(Ecosystem::Cargo, CargoCrawler.crawl_all(options)),
                 crawl!(
                     Ecosystem::Gem,
@@ -2400,7 +2400,10 @@ mod tests {
             }};
         }
         serial!(Ecosystem::Npm, NpmCrawler.crawl_all(&options).await);
-        serial!(Ecosystem::Pypi, PythonCrawler.crawl_all(&options).await);
+        serial!(
+            Ecosystem::Pypi,
+            PythonCrawler::new().crawl_all(&options).await
+        );
         serial!(Ecosystem::Cargo, CargoCrawler.crawl_all(&options).await);
         serial!(Ecosystem::Gem, RubyCrawler.crawl_all(&options).await);
         serial!(Ecosystem::Golang, GoCrawler.crawl_all(&options).await);

crates/socket-patch-cli/tests/in_process_redirect_poetry.rs

@@ -403,7 +403,10 @@ async fn scan_output(root: &Path, server: &MockServer, extra: &[&str]) -> std::p
     ] {
         cmd.env_remove(key);
     }
+    // Hermetic against the runner's own Python user site, which a
+    // `--system-site-packages` venv reaches (#409).
     cmd.env("SOCKET_TELEMETRY_DISABLED", "1")
+        .env("PYTHONNOUSERSITE", "1")
         .args(["scan", "--mode", "hosted", "--yes", "--cwd"])
         .arg(root)
         .args([
@@ -490,6 +493,84 @@ async fn stale_python_install_warns_and_cannot_attest_even_on_rescan() {
     }
 }
 
+/// A `.venv` created with `--system-site-packages` whose base interpreter
+/// lives at `root/base`; `bytes` is installed in the BASE interpreter only,
+/// which is where pip leaves a release it finds already satisfied there.
+/// Returns the base copy's file.
+fn install_behind_system_site_venv(root: &Path, bytes: &[u8]) -> std::path::PathBuf {
+    let base = root.join("base");
+    let (home, stdlib) = if cfg!(windows) {
+        (base.clone(), base.join("Lib"))
+    } else {
+        (base.join("bin"), base.join("lib").join("python3.12"))
+    };
+    std::fs::create_dir_all(&home).unwrap();
+    std::fs::create_dir_all(&stdlib).unwrap();
+    std::fs::write(stdlib.join("os.py"), "").unwrap();
+    let file = install_package(root, "base", bytes);
+    // The project venv (`write_project` made its empty site-packages)
+    // reaches the base interpreter.
+    std::fs::write(
+        root.join(".venv").join("pyvenv.cfg"),
+        format!(
+            "home = {}\ninclude-system-site-packages = true\nversion = 3.12.4\n",
+            home.display()
+        ),
+    )
+    .unwrap();
+    file
+}
+
+/// #409: pip leaves a release the base interpreter already has where it
+/// is, so behind a `--system-site-packages` venv the unpatched base copy is
+/// the one the build imports. It must get the stale-install warning, and
+/// `--vex` must not attest from the lock pin as if nothing were installed.
+#[tokio::test]
+async fn stale_base_copy_behind_system_site_venv_warns_and_cannot_attest() {
+    let server = MockServer::start().await;
+    mock_api(&server).await;
+    let tmp = tempfile::tempdir().unwrap();
+    write_project(tmp.path());
+    let installed = install_behind_system_site_venv(tmp.path(), UPSTREAM);
+    let vex = tmp.path().join("out.vex.json");
+    let out = scan_output(
+        tmp.path(),
+        &server,
+        &["--json", "--vex", vex.to_str().unwrap()],
+    )
+    .await;
+    let json = envelope(&out);
+    assert_eq!(out.status.code(), Some(1), "{json}");
+    assert!(stale_warning(&json), "{json}");
+    assert_eq!(json["error"]["code"], "no_applicable_patches", "{json}");
+    assert!(!vex.exists(), "stale base bytes cannot produce a VEX file");
+    assert_eq!(std::fs::read(installed).unwrap(), UPSTREAM);
+}
+
+/// #409: once the venv holds its own patched copy (`pip install
+/// --force-reinstall` leaves the base copy in place), the base copy is
+/// shadowed: no stale warning, and the venv's verified bytes attest.
+#[tokio::test]
+async fn venv_copy_shadows_stale_base_copy_behind_system_site_venv() {
+    let server = MockServer::start().await;
+    mock_api(&server).await;
+    let tmp = tempfile::tempdir().unwrap();
+    write_project(tmp.path());
+    install_behind_system_site_venv(tmp.path(), UPSTREAM);
+    install_package(tmp.path(), ".venv", PATCHED);
+    let vex = tmp.path().join("out.vex.json");
+    let out = scan_output(
+        tmp.path(),
+        &server,
+        &["--json", "--vex", vex.to_str().unwrap()],
+    )
+    .await;
+    let json = envelope(&out);
+    assert!(out.status.success(), "{json}");
+    assert!(!stale_warning(&json), "{json}");
+    assert_eq!(json["vex"]["statements"], 1, "{json}");
+}
+
 #[tokio::test]
 async fn patched_python_install_attests_without_a_stale_warning() {
     let server = MockServer::start().await;