Opening /dev/null leads to panic: not yet implemented

[mejedi]

Describe the bug

If a program attempts to open /dev/null or any other device file, Wasmer panics with the error saying "not yet implemented".

$ echo "`wasmer -V` | `rustc -V` | `uname -m`"
zsh: command not found: rustc
wasmer 0.17.1 |  | x86_64

Steps to reproduce

1. Put the following code in opendevnull.c:

#include <stdio.h>
int main() {
  fputs("open: /dev/null\n", stderr);
  if (fopen("/dev/null", "r")==NULL) perror("open");
  return 0;
}

2. Compile using wasienv:

$ wasicc opendevnull.c -o opendevnull.wasm

3. Run

$ wasmer run --dir=/ opendevnull.wasm
open: /dev/null
thread 'main' panicked at 'not yet implemented: state::get_inode_at_path unknown file type: not file, directory, or symlink', lib/wasi/src/state/mod.rs:818:33
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
Error: error: User(Any)

Expected behavior

Opening /dev/null should've succeeded.

Actual behavior

Wasmer panics with the error saying "not yet implemented.

Additional context

I want to use the existing test suite to ensure that the program ported to Wasmer works as expected. I'd like to have as few modifications to the test suite as possible.

The test suite depends heavily on /dev/null. I could make it work for the output going to /dev/null easily with --mapdir feature (so that it actually goes to a file named "null" in a temporary dir). Unfortunately, /dev/null is also often used for input and I don't have a workaround.