stdio.js•6.69 kB
import spawn from 'cross-spawn';
import process from 'node:process';
import { PassThrough } from 'node:stream';
import { ReadBuffer, serializeMessage } from '../shared/stdio.js';
/**
* Environment variables to inherit by default, if an environment is not explicitly given.
*/
export const DEFAULT_INHERITED_ENV_VARS = process.platform === 'win32'
? [
'APPDATA',
'HOMEDRIVE',
'HOMEPATH',
'LOCALAPPDATA',
'PATH',
'PROCESSOR_ARCHITECTURE',
'SYSTEMDRIVE',
'SYSTEMROOT',
'TEMP',
'USERNAME',
'USERPROFILE',
'PROGRAMFILES'
]
: /* list inspired by the default env inheritance of sudo */
['HOME', 'LOGNAME', 'PATH', 'SHELL', 'TERM', 'USER'];
/**
* Returns a default environment object including only environment variables deemed safe to inherit.
*/
export function getDefaultEnvironment() {
const env = {};
for (const key of DEFAULT_INHERITED_ENV_VARS) {
const value = process.env[key];
if (value === undefined) {
continue;
}
if (value.startsWith('()')) {
// Skip functions, which are a security risk.
continue;
}
env[key] = value;
}
return env;
}
/**
* Client transport for stdio: this will connect to a server by spawning a process and communicating with it over stdin/stdout.
*
* This transport is only available in Node.js environments.
*/
export class StdioClientTransport {
constructor(server) {
this._abortController = new AbortController();
this._readBuffer = new ReadBuffer();
this._stderrStream = null;
this._serverParams = server;
if (server.stderr === 'pipe' || server.stderr === 'overlapped') {
this._stderrStream = new PassThrough();
}
}
/**
* Starts the server process and prepares to communicate with it.
*/
async start() {
if (this._process) {
throw new Error('StdioClientTransport already started! If using Client class, note that connect() calls start() automatically.');
}
return new Promise((resolve, reject) => {
var _a, _b, _c, _d, _e;
this._process = spawn(this._serverParams.command, (_a = this._serverParams.args) !== null && _a !== void 0 ? _a : [], {
// merge default env with server env because mcp server needs some env vars
env: {
...getDefaultEnvironment(),
...this._serverParams.env
},
stdio: ['pipe', 'pipe', (_b = this._serverParams.stderr) !== null && _b !== void 0 ? _b : 'inherit'],
shell: false,
signal: this._abortController.signal,
windowsHide: process.platform === 'win32' && isElectron(),
cwd: this._serverParams.cwd
});
this._process.on('error', error => {
var _a, _b;
if (error.name === 'AbortError') {
// Expected when close() is called.
(_a = this.onclose) === null || _a === void 0 ? void 0 : _a.call(this);
return;
}
reject(error);
(_b = this.onerror) === null || _b === void 0 ? void 0 : _b.call(this, error);
});
this._process.on('spawn', () => {
resolve();
});
this._process.on('close', _code => {
var _a;
this._process = undefined;
(_a = this.onclose) === null || _a === void 0 ? void 0 : _a.call(this);
});
(_c = this._process.stdin) === null || _c === void 0 ? void 0 : _c.on('error', error => {
var _a;
(_a = this.onerror) === null || _a === void 0 ? void 0 : _a.call(this, error);
});
(_d = this._process.stdout) === null || _d === void 0 ? void 0 : _d.on('data', chunk => {
this._readBuffer.append(chunk);
this.processReadBuffer();
});
(_e = this._process.stdout) === null || _e === void 0 ? void 0 : _e.on('error', error => {
var _a;
(_a = this.onerror) === null || _a === void 0 ? void 0 : _a.call(this, error);
});
if (this._stderrStream && this._process.stderr) {
this._process.stderr.pipe(this._stderrStream);
}
});
}
/**
* The stderr stream of the child process, if `StdioServerParameters.stderr` was set to "pipe" or "overlapped".
*
* If stderr piping was requested, a PassThrough stream is returned _immediately_, allowing callers to
* attach listeners before the start method is invoked. This prevents loss of any early
* error output emitted by the child process.
*/
get stderr() {
var _a, _b;
if (this._stderrStream) {
return this._stderrStream;
}
return (_b = (_a = this._process) === null || _a === void 0 ? void 0 : _a.stderr) !== null && _b !== void 0 ? _b : null;
}
/**
* The child process pid spawned by this transport.
*
* This is only available after the transport has been started.
*/
get pid() {
var _a, _b;
return (_b = (_a = this._process) === null || _a === void 0 ? void 0 : _a.pid) !== null && _b !== void 0 ? _b : null;
}
processReadBuffer() {
var _a, _b;
while (true) {
try {
const message = this._readBuffer.readMessage();
if (message === null) {
break;
}
(_a = this.onmessage) === null || _a === void 0 ? void 0 : _a.call(this, message);
}
catch (error) {
(_b = this.onerror) === null || _b === void 0 ? void 0 : _b.call(this, error);
}
}
}
async close() {
this._abortController.abort();
this._process = undefined;
this._readBuffer.clear();
}
send(message) {
return new Promise(resolve => {
var _a;
if (!((_a = this._process) === null || _a === void 0 ? void 0 : _a.stdin)) {
throw new Error('Not connected');
}
const json = serializeMessage(message);
if (this._process.stdin.write(json)) {
resolve();
}
else {
this._process.stdin.once('drain', resolve);
}
});
}
}
function isElectron() {
return 'type' in process;
}
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