add a wasi-test to show a dir_fd always gets ERRNO_BADF on appropriate fd_ operations (#6197)

* add a wasi-test to show a dir_fd always gets ERRNO_BADF on appropriate fd_ operations.

This is a conformance test for the current behavior of preview 1 in wasi-common. It is debatable whether this is the right errno, I think for most of these ERRNO_ISDIR would be more descriptive, but this is the behavior we have.

* Add comments to all the fd op failures explaining closest linux/posix behavior

crates/test-programs/wasi-tests/src/bin/dir_fd_op_failures.rs

@@ -0,0 +1,99 @@
+use std::{env, process};
+use wasi_tests::open_scratch_directory;
+
+unsafe fn test_fd_dir_ops(dir_fd: wasi::Fd) {
+    let stat = wasi::fd_filestat_get(dir_fd).expect("failed to fdstat");
+    assert_eq!(stat.filetype, wasi::FILETYPE_DIRECTORY);
+
+    let mut read_buf = vec![0; 128].into_boxed_slice();
+    let iovec = wasi::Iovec {
+        buf: read_buf.as_mut_ptr(),
+        buf_len: read_buf.len(),
+    };
+    let r = wasi::fd_read(dir_fd, &[iovec]);
+    // On posix, this fails with ERRNO_ISDIR:
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_read error");
+
+    let r = wasi::fd_pread(dir_fd, &[iovec], 0);
+    // On posix, this fails with ERRNO_ISDIR
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_pread error");
+
+    let write_buf = vec![0; 128].into_boxed_slice();
+    let ciovec = wasi::Ciovec {
+        buf: write_buf.as_ptr(),
+        buf_len: write_buf.len(),
+    };
+    let r = wasi::fd_write(dir_fd, &[ciovec]);
+    // Same behavior as specified by POSIX:
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_write error");
+
+    let r = wasi::fd_pwrite(dir_fd, &[ciovec], 0);
+    // Same behavior as specified by POSIX:
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_pwrite error");
+
+    // Divergence from posix: lseek(dirfd) will return 0
+    let r = wasi::fd_seek(dir_fd, 0, wasi::WHENCE_CUR);
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_seek WHENCE_CUR error");
+    let r = wasi::fd_seek(dir_fd, 0, wasi::WHENCE_SET);
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_seek WHENCE_SET error");
+    let r = wasi::fd_seek(dir_fd, 0, wasi::WHENCE_END);
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_seek WHENCE_END error");
+
+    // Tell isnt in posix, its basically lseek with WHENCE_CUR above
+    let r = wasi::fd_tell(dir_fd);
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_tell error");
+
+    // posix_fadvise(dirfd, 0, 0, POSIX_FADV_DONTNEED) will return 0 on linux.
+    // not available on mac os.
+    let r = wasi::fd_advise(dir_fd, 0, 0, wasi::ADVICE_DONTNEED);
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_advise error");
+
+    // fallocate(dirfd, FALLOC_FL_ZERO_RANGE, 0, 1) will fail with errno EBADF on linux.
+    // not available on mac os.
+    let r = wasi::fd_allocate(dir_fd, 0, 0);
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_allocate error");
+
+    // fdatasync(dirfd) will return 0 on linux.
+    // not available on mac os.
+    let r = wasi::fd_datasync(dir_fd);
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_datasync error");
+
+    // fsync(dirfd) will return 0 on linux.
+    // not available on mac os.
+    let r = wasi::fd_sync(dir_fd);
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_sync error");
+
+    // fcntl(dirfd,  F_SETFL, O_NONBLOCK) will return 0 on linux.
+    // not available on mac os.
+    let r = wasi::fd_fdstat_set_flags(dir_fd, wasi::FDFLAGS_NONBLOCK);
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_fdstat_set_flags error");
+
+    // ftruncate(dirfd, 1) will fail with errno EINVAL on posix.
+    // here, we fail with EBADF instead:
+    let r = wasi::fd_filestat_set_size(dir_fd, 0);
+    assert_eq!(r, Err(wasi::ERRNO_BADF), "fd_filestat_set_size error");
+}
+
+fn main() {
+    let mut args = env::args();
+    let prog = args.next().unwrap();
+    let arg = if let Some(arg) = args.next() {
+        arg
+    } else {
+        eprintln!("usage: {} <scratch directory>", prog);
+        process::exit(1);
+    };
+
+    // Open scratch directory
+    let dir_fd = match open_scratch_directory(&arg) {
+        Ok(dir_fd) => dir_fd,
+        Err(err) => {
+            eprintln!("{}", err);
+            process::exit(1)
+        }
+    };
+
+    unsafe {
+        test_fd_dir_ops(dir_fd);
+    }
+}