fix(fspy): handle null ObjectName and Buffer in UNICODE_STRING on Windows

When oxlint runs with --type-aware flag, it spawns tsgolint which triggers
code paths where ObjectName or its Buffer can be null. This caused a panic
in slice::from_raw_parts due to null pointer.

Fixes:
- Check for null ObjectName before dereferencing in POBJECT_ATTRIBUTES
- Handle null/empty Buffer in get_u16_str by returning empty slice
- Fix UNICODE_STRING.Length interpretation (bytes, not char count)

Also adds oxlint_type_aware test to verify the fix and prevent regression.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: branchseer

crates/fspy/tests/oxlint.rs

@@ -1,28 +1,47 @@
 mod test_utils;
 
-use std::{env::vars_os, process::Stdio};
+use std::{env::vars_os, ffi::OsString};
 
 use fspy::{AccessMode, PathAccessIterable};
 use test_log::test;
 
-/// Find the oxlint executable in test_bins
-fn find_oxlint() -> std::path::PathBuf {
-    let test_bins_dir = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
+/// Get the test_bins/.bin directory path
+fn test_bins_bin_dir() -> std::path::PathBuf {
+    std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
         .parent()
         .unwrap()
         .join("vite_task_bin")
         .join("test_bins")
         .join("node_modules")
-        .join(".bin");
+        .join(".bin")
+}
 
+/// Find the oxlint executable in test_bins
+fn find_oxlint() -> std::path::PathBuf {
+    let test_bins_dir = test_bins_bin_dir();
     which::which_in("oxlint", Some(&test_bins_dir), std::env::current_dir().unwrap())
         .expect("oxlint not found in test_bins/node_modules/.bin")
 }
 
 async fn track_oxlint(dir: &std::path::Path, args: &[&str]) -> anyhow::Result<PathAccessIterable> {
     let oxlint_path = find_oxlint();
     let mut command = fspy::Command::new(&oxlint_path);
-    command.args(args).stdout(Stdio::null()).stderr(Stdio::null()).envs(vars_os()).current_dir(dir);
+
+    // Build PATH with test_bins/.bin prepended so oxlint can find tsgolint
+    let test_bins_dir = test_bins_bin_dir();
+    let new_path = if let Some(existing_path) = std::env::var_os("PATH") {
+        let mut paths = vec![test_bins_dir.as_os_str().to_owned()];
+        paths.extend(std::env::split_paths(&existing_path).map(|p| p.into_os_string()));
+        std::env::join_paths(paths)?
+    } else {
+        OsString::from(&test_bins_dir)
+    };
+
+    command
+        .args(args)
+        .envs(vars_os().filter(|(k, _)| !k.eq_ignore_ascii_case("PATH")))
+        .env("PATH", new_path)
+        .current_dir(dir);
 
     let child = command.spawn().await?;
     let termination = child.wait_handle.await?;
@@ -64,3 +83,38 @@ async fn oxlint_reads_directory() -> anyhow::Result<()> {
     test_utils::assert_contains(&accesses, &tmpdir_path, AccessMode::READ_DIR);
     Ok(())
 }
+
+/// Test oxlint with TypeScript type-aware linting (--tsconfig)
+/// This reproduces a crash in fspy_preload_windows on Windows:
+/// "unsafe precondition(s) violated: slice::from_raw_parts requires the pointer to be aligned and non-null"
+#[test(tokio::test)]
+async fn oxlint_type_aware() -> anyhow::Result<()> {
+    let tmpdir = tempfile::tempdir()?;
+
+    // Create a simple TypeScript file
+    let ts_file = tmpdir.path().join("index.ts");
+    std::fs::write(
+        &ts_file,
+        r#"
+import type { Foo } from './types';
+declare const _foo: Foo;
+"#,
+    )?;
+
+    // Run oxlint without --type-aware first
+    let accesses = track_oxlint(tmpdir.path(), &[""]).await?;
+    let access_to_types_ts = accesses.iter().find(|access| {
+        let os_str = access.path.to_cow_os_str();
+        os_str.as_encoded_bytes().ends_with(b"\\types.ts")
+            || os_str.as_encoded_bytes().ends_with(b"/types.ts")
+    });
+    assert_eq!(access_to_types_ts, None, "oxlint should not read types.ts without --type-aware");
+
+    // Run oxlint with --type-aware to enable type-aware linting
+    let accesses = track_oxlint(tmpdir.path(), &["--type-aware"]).await?;
+
+    // Check that oxlint read types.ts
+    test_utils::assert_contains(&accesses, &tmpdir.path().join("types.ts"), AccessMode::READ);
+
+    Ok(())
+}

crates/fspy_preload_windows/src/windows/convert.rs

@@ -50,7 +50,11 @@ impl ToAbsolutePath for POBJECT_ATTRIBUTES {
         self,
         f: F,
     ) -> winsafe::SysResult<R> {
-        let filename_str = unsafe { get_u16_str(&*(*self).ObjectName) };
+        let filename_str = if let Some(object_name) = unsafe { (*self).ObjectName.as_ref() } {
+            unsafe { get_u16_str(object_name) }
+        } else {
+            U16Str::from_slice(&[])
+        };
         let filename_slice = filename_str.as_slice();
         let is_absolute = (filename_slice.get(0) == Some(&b'\\'.into())
         && filename_slice.get(1) == Some(&b'\\'.into())) // \\...

crates/fspy_preload_windows/src/windows/winapi_utils.rs

@@ -29,8 +29,16 @@ pub fn ck_long(val: c_long) -> winsafe::SysResult<()> {
 }
 
 pub unsafe fn get_u16_str(ustring: &UNICODE_STRING) -> &U16Str {
-    let chars =
-        unsafe { slice::from_raw_parts((*ustring).Buffer, (*ustring).Length.try_into().unwrap()) };
+    // https://learn.microsoft.com/en-us/windows/win32/api/subauth/ns-subauth-unicode_string
+    // UNICODE_STRING.Length is in bytes
+    let u16_count = ustring.Length / 2;
+    let chars: &[u16] = if u16_count == 0 {
+        // If length is zero, we cann't use slice::from_raw_parts as it requires a non-null pointer but
+        // Buffer may be null in that case.
+        &[]
+    } else {
+        unsafe { slice::from_raw_parts((*ustring).Buffer, u16_count.try_into().unwrap()) }
+    };
     match U16CStr::from_slice_truncate(chars) {
         Ok(ok) => ok.as_ustr(),
         Err(_) => chars.into(),

crates/fspy_shared/src/ipc/mod.rs

@@ -32,7 +32,7 @@ impl Debug for AccessMode {
     }
 }
 
-#[derive(Encode, BorrowDecode, Debug, Clone, Copy)]
+#[derive(Encode, BorrowDecode, Debug, Clone, Copy, PartialEq, Eq)]
 pub struct PathAccess<'a> {
     pub mode: AccessMode,
     pub path: &'a NativeStr,

crates/vite_task_bin/test_bins/package.json

@@ -12,6 +12,7 @@
     "@yarnpkg/shell": "catalog:",
     "cross-env": "^10.1.0",
     "oxlint": "catalog:",
+    "oxlint-tsgolint": "catalog:",
     "vite-task-test-bins": "link:"
   }
 }