better error message for wasi

[gengjiawen]

when preopens directory not really exists, Node.js failed with

node[55811]: ../src/node_wasi.cc:88:node::wasi::WASI::WASI(node::Environment *, Local<v8::Object>, uvwasi_options_t *): Assertion `(uvwasi_init(&uvw_, options)) == (0)' failed.
 1: 0x100081683 node::Abort() [/usr/local/bin/node]
 2: 0x10008142b node::AppendExceptionLine(node::Environment*, v8::Local<v8::Value>, v8::Local<v8::Message>, node::ErrorHandlingMode) [/usr/local/bin/node]
 3: 0x1000e58be node::wasi::WASI::WASI(node::Environment*, v8::Local<v8::Object>, uvwasi_options_s*) [/usr/local/bin/node]
 4: 0x1000e5e5b node::wasi::WASI::New(v8::FunctionCallbackInfo<v8::Value> const&) [/usr/local/bin/node]
 5: 0x1001ec8d0 v8::internal::FunctionCallbackArguments::Call(v8::internal::CallHandlerInfo) [/usr/local/bin/node]
 6: 0x1001ebb9d v8::internal::MaybeHandle<v8::internal::Object> v8::internal::(anonymous namespace)::HandleApiCallHelper<true>(v8::internal::Isolate*, v8::internal::Handle<v8::internal::HeapObject>, v8::internal::Handle<v8::internal::HeapObject>, v8::internal::Handle<v8::internal::FunctionTemplateInfo>, v8::internal::Handle<v8::internal::Object>, v8::internal::BuiltinArguments) [/usr/local/bin/node]
 7: 0x1001eb557 v8::internal::Builtin_Impl_HandleApiCall(v8::internal::BuiltinArguments, v8::internal::Isolate*) [/usr/local/bin/node]
 8: 0x100951939 Builtins_CEntry_Return1_DontSaveFPRegs_ArgvOnStack_BuiltinExit [/usr/local/bin/node]
fish: 'node --experimental-wasi-unstab…' terminated by signal SIGABRT (Abort)

Repro code:

"use strict";
const fs = require('fs');
const { WASI } = require('wasi');
const wasi = new WASI({
 args: process.argv,
 env: process.env,
 preopens: {
 '/sandbox': '/not/real/path'
 }
})

I think maybe we can add some pre-check here ? The current error message doesn't provide much information.

cc @nodejs/wasi

[cjihrig]

Thanks for reporting. I'll send a fix.