process: add notice message when process.cwd() failed.

Author: Tseian

src/node_process_methods.cc

@@ -163,9 +163,16 @@ static void Cwd(const FunctionCallbackInfo<Value>& args) {
   size_t cwd_len = sizeof(buf);
   int err = uv_cwd(buf, &cwd_len);
   if (err) {
-    std::string msg =
+    std::string err_msg =
         std::string("process.cwd failed with error ") + uv_strerror(err);
-    return env->ThrowUVException(err, "uv_cwd", msg.c_str());
+        if (err == UV_ENOENT) {
+      // If err == UV_ENOENT it is necessary to notice the user
+      // that the current working dir was likely removed.
+      err_msg = err_msg +
+          std::string(", the current working directory was likely removed ") +
+          std::string("without changing the working directory");
+    }
+    return env->ThrowUVException(err, "uv_cwd", err_msg.c_str());
   }
   Local<String> cwd;
   if (String::NewFromUtf8(env->isolate(), buf, NewStringType::kNormal, cwd_len)

test/known_issues/test-cwd-enoent-file.js

@@ -23,7 +23,7 @@ if (process.argv[2] === 'child') {
   process.chdir(dir);
   fs.rmdirSync(dir);
   assert.throws(process.cwd,
-                /^Error: ENOENT: process\.cwd failed with error no such file or directory, uv_cwd$/);
+                /^Error: ENOENT: process\.cwd failed with error no such file or directory, the current working directory was likely removed without changing the working directory, uv_cwd$/);
 
   const r = cp.spawnSync(process.execPath, [__filename, 'child']);
 

test/parallel/test-cwd-enoent-improved-message.js

@@ -26,6 +26,7 @@ assert.throws(
   () => process.cwd(),
   {
     code: 'ENOENT',
-    message: 'ENOENT: process.cwd failed with error no such file or directory, uv_cwd',
+    message: 'ENOENT: process.cwd failed with error no such file or directory,' +
+      ' the current working directory was likely removed without changing the working directory, uv_cwd',
   }
 );