Disallow empty path on path_open

This commit makes `path_open` return `inval` when passed an empty path.
This behavior is consistent with other Wasm runtimes (Wasmtime, Wasmer,
Node, WAMR, WasmEdge).

fixes tetratelabs#2222

imports/wasi_snapshot_preview1/fs.go

@@ -1581,7 +1581,6 @@ func pathOpenFn(_ context.Context, mod api.Module, params []uint64) experimental
 
 	path := uint32(params[2])
 	pathLen := uint32(params[3])
-
 	oflags := uint16(params[4])
 
 	rights := uint32(params[5])
@@ -1596,6 +1595,10 @@ func pathOpenFn(_ context.Context, mod api.Module, params []uint64) experimental
 		return errno
 	}
 
+	if pathLen == 0 {
+		return experimentalsys.EINVAL
+	}
+
 	fileOpenFlags := openFlags(dirflags, oflags, fdflags, rights)
 	isDir := fileOpenFlags&experimentalsys.O_DIRECTORY != 0
 

imports/wasi_snapshot_preview1/fs_test.go

@@ -4095,6 +4095,17 @@ func Test_pathOpen_Errors(t *testing.T) {
 			expectedLog: `
 ==> wasi_snapshot_preview1.path_open(fd=3,dirflags=,path=OOM(65536,4),oflags=,fs_rights_base=,fs_rights_inheriting=,fdflags=)
 <== (opened_fd=,errno=EFAULT)
+`,
+		},
+		{
+			name:          "empty path",
+			fd:            sys.FdPreopen,
+			path:          0,
+			pathLen:       0,
+			expectedErrno: wasip1.ErrnoInval,
+			expectedLog: `
+==> wasi_snapshot_preview1.path_open(fd=3,dirflags=,path=,oflags=,fs_rights_base=,fs_rights_inheriting=,fdflags=)
+<== (opened_fd=,errno=EINVAL)
 `,
 		},
 		{