test(fs): cover recursive mkdir options-object decoding

changelog.d/8309-mkdir-options-object-regression.md

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+Add an end-to-end regression test for recursive `fs.mkdirSync` calls that pass an options object.

crates/perry/tests/issue_8122_fs_mkdir_options_object.rs

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+//! Regression test for the fs options-object crash fixed alongside #8122.
+//!
+//! `mkdirSync(path, { recursive: true })` passes an object where the runtime
+//! also accepts a string mode. Before #8204, the generic string helper accepted
+//! any plausible NaN-boxed pointer and read the options object's ShapeId as a
+//! `StringHeader::byte_len`. ShapeIds have the high bit set, so the runtime
+//! attempted a roughly 2 GiB string copy and crashed in `memcpy`.
+//!
+//! Claude Code exercises this exact call shape during normal startup, while its
+//! `--version` fast path exits before touching the filesystem.
+
+use std::path::{Path, PathBuf};
+use std::process::Command;
+
+fn perry_bin() -> PathBuf {
+    PathBuf::from(env!("CARGO_BIN_EXE_perry"))
+}
+
+const SOURCE: &str = r#"
+import * as fs from "node:fs";
+
+const root = ".perry-issue-8122-mkdir";
+fs.mkdirSync(root + "/a/b", { recursive: true });
+const ok = fs.statSync(root + "/a/b").isDirectory();
+console.log(ok ? "PASS" : "FAIL");
+fs.rmSync(root, { recursive: true, force: true });
+"#;
+
+fn compile(dir: &Path, entry: &Path, output: &Path) {
+    let compile = Command::new(perry_bin())
+        .current_dir(dir)
+        .arg("compile")
+        .arg(entry)
+        .arg("-o")
+        .arg(output)
+        .arg("--no-cache")
+        .output()
+        .expect("run perry compile");
+    assert!(
+        compile.status.success(),
+        "perry compile failed\nstdout:\n{}\nstderr:\n{}",
+        String::from_utf8_lossy(&compile.stdout),
+        String::from_utf8_lossy(&compile.stderr)
+    );
+}
+
+#[test]
+fn recursive_mkdir_options_object_is_not_decoded_as_a_string() {
+    let dir = tempfile::tempdir().expect("tempdir");
+    let entry = dir.path().join("main.ts");
+    let output = dir.path().join("main_bin");
+    std::fs::write(&entry, SOURCE).expect("write entry");
+
+    compile(dir.path(), &entry, &output);
+
+    let run = Command::new(&output)
+        .current_dir(dir.path())
+        .output()
+        .expect("run compiled binary");
+    let stdout = String::from_utf8_lossy(&run.stdout);
+    assert!(
+        run.status.success() && stdout.contains("PASS"),
+        "recursive mkdir with an options object failed (status {:?})\nstdout:\n{}\nstderr:\n{}",
+        run.status,
+        stdout,
+        String::from_utf8_lossy(&run.stderr)
+    );
+}