Keep user Composer config out of test CLIs

From /code-review high: the Composer suites only dropped an ambient
COMPOSER_VENDOR_DIR. The crawler also reads vendor-dir from the
user-level config.json, which it finds through COMPOSER_HOME or an
absolute XDG_CONFIG_HOME, so a developer whose Composer config sets
vendor-dir still failed 2 e2e_composer tests and 1
e2e_composer_version_identity test.

hermetic::Extra::Composer now removes every ambient COMPOSER_* var
and pins COMPOSER_HOME to a missing directory, which outranks
XDG_CONFIG_HOME and holds no config. Both Composer suites use it, and
spawn_env_hygiene checks the scrub.

Refs #823

Assisted-by: Claude Code:claude-opus-5-5

Author: claude

crates/socket-patch-cli/tests/common/hermetic.rs

@@ -209,6 +209,14 @@ pub enum Extra {
     /// Every `POETRY_*` var: Poetry reads any config key from
     /// `POETRY_<KEY>` (`POETRY_VIRTUALENVS_PATH`, repository URLs, ...).
     Poetry,
+    /// Every `COMPOSER_*` var, then `COMPOSER_HOME` pinned to a missing
+    /// directory. The crawler resolves a project's vendor directory from
+    /// `COMPOSER_VENDOR_DIR`, else the user-level `config.json` in the
+    /// Composer home, which it finds through `COMPOSER_HOME` or an
+    /// absolute `XDG_CONFIG_HOME`; any of them moves the crawl off the
+    /// fixture's `vendor/`. The pin outranks `XDG_CONFIG_HOME` and holds
+    /// no config. Run it before the suite sets its own `COMPOSER_*` values.
+    Composer,
 }
 
 /// Apply each of `extras` to `cmd` (see [`Extra`]). Run it before
@@ -279,6 +287,14 @@ pub fn scrub_extra(cmd: &mut Command, extras: &[Extra]) {
                     }
                 }
             }
+            Extra::Composer => {
+                for (key, _) in std::env::vars_os() {
+                    if key.to_string_lossy().starts_with("COMPOSER_") {
+                        cmd.env_remove(&key);
+                    }
+                }
+                cmd.env("COMPOSER_HOME", "/nonexistent/composer-home");
+            }
         }
     }
 }

crates/socket-patch-cli/tests/e2e_composer.rs

@@ -48,20 +48,23 @@ async fn start_proxy() -> MockServer {
 /// `--proxy-url` pins). The scans are unscoped, so an activated venv is
 /// scrubbed and `HOME` points at a stand-in (`jvm_env::isolate_cli`): the
 /// developer's venv, `~/.m2` or user site-packages would add packages to
-/// the counts these tests assert. An ambient `COMPOSER_VENDOR_DIR` would
-/// move the vendor directory the crawler reads off the fixture's.
+/// the counts these tests assert. `Extra::Composer` keeps an ambient
+/// `COMPOSER_VENDOR_DIR` or user-level Composer config from moving the
+/// vendor directory the crawler reads off the fixture's.
 async fn run(args: &[&str], cwd: &std::path::Path, proxy_url: &str) -> Output {
     let mut args: Vec<String> = args.iter().map(|s| s.to_string()).collect();
     args.extend(["--proxy-url".to_string(), proxy_url.to_string()]);
     let cwd = cwd.to_path_buf();
     tokio::task::spawn_blocking(move || {
         let arg_refs: Vec<&str> = args.iter().map(String::as_str).collect();
         let mut cmd = hermetic::command(&binary());
-        hermetic::scrub_extra(&mut cmd, &[hermetic::Extra::Venv]);
+        hermetic::scrub_extra(
+            &mut cmd,
+            &[hermetic::Extra::Venv, hermetic::Extra::Composer],
+        );
         common::jvm_env::isolate_cli(&mut cmd);
         cmd.args(&arg_refs)
             .current_dir(&cwd)
-            .env_remove("COMPOSER_VENDOR_DIR")
             .output()
             .expect("Failed to run socket-patch binary")
     })

crates/socket-patch-cli/tests/e2e_composer_version_identity.rs

@@ -183,15 +183,18 @@ async fn mount_api(server: &MockServer, prebuilt: bool) {
 }
 
 /// The built binary in the hermetic `SOCKET_*` environment, so the
-/// assertions reflect only the argv. The scans are unscoped, so an
-/// activated venv is scrubbed and `HOME` points at a stand-in
-/// (`jvm_env::isolate_cli`), and an ambient `COMPOSER_VENDOR_DIR` can't move
+/// assertions reflect only the argv. Its scans and `vex` runs crawl every
+/// ecosystem, so an activated venv is scrubbed and `HOME` points at a
+/// stand-in (`jvm_env::isolate_cli`), and `Extra::Composer` keeps an
+/// ambient `COMPOSER_VENDOR_DIR` or user-level Composer config from moving
 /// the vendor directory off the fixture's.
 fn cli() -> Command {
     let mut cmd = hermetic::binary_command();
-    hermetic::scrub_extra(&mut cmd, &[hermetic::Extra::Venv]);
+    hermetic::scrub_extra(
+        &mut cmd,
+        &[hermetic::Extra::Venv, hermetic::Extra::Composer],
+    );
     prebuilt_common::jvm_env::isolate_cli(&mut cmd);
-    cmd.env_remove("COMPOSER_VENDOR_DIR");
     cmd
 }
 

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

@@ -454,6 +454,39 @@ fn bundle_extra_sweeps_every_bundler_override() {
     );
 }
 
+#[test]
+#[serial]
+fn composer_extra_sweeps_overrides_and_pins_an_empty_home() {
+    with_ambient(
+        &[
+            ("COMPOSER_VENDOR_DIR", "third"),
+            ("COMPOSER_HOME", "/ambient/composer"),
+            ("COMPOSER_CACHE_DIR", "/ambient/composer-cache"),
+            ("XDG_CONFIG_HOME", "/ambient/config"),
+        ],
+        || {
+            let mut cmd = Command::new("socket-patch");
+            hermetic::scrub_extra(&mut cmd, &[Extra::Composer]);
+            let env = effective_env(&cmd);
+            assert_eq!(get(&env, "COMPOSER_VENDOR_DIR"), None);
+            assert_eq!(get(&env, "COMPOSER_CACHE_DIR"), None);
+            // The pin outranks XDG_CONFIG_HOME in the Composer home lookup.
+            assert_eq!(
+                get(&env, "COMPOSER_HOME"),
+                Some("/nonexistent/composer-home")
+            );
+            assert_eq!(get(&env, "XDG_CONFIG_HOME"), Some("/ambient/config"));
+
+            // A suite's own COMPOSER_HOME, set after the scrub, survives.
+            cmd.env("COMPOSER_HOME", "/fixture/home");
+            assert_eq!(
+                get(&effective_env(&cmd), "COMPOSER_HOME"),
+                Some("/fixture/home")
+            );
+        },
+    );
+}
+
 #[test]
 #[serial]
 fn extra_seeds_are_scrubbed_whatever_the_ambient_value() {