Colin McDonnell
84 lines
2.4 KiB
TypeScript
84 lines
2.4 KiB
TypeScript
import { spawnSync } from "node:child_process";
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interface ShellOptions {
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cwd?: string;
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encoding?:
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| "utf-8"
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| "utf8"
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| "ascii"
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| "base64"
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| "base64url"
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| "hex"
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| "latin1"
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| "ucs-2"
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| "ucs2"
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| "utf16le";
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log?: boolean;
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onError?: (result: { status: number; stdout: string; stderr: string }) => void;
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}
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/**
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* Execute a shell command safely using spawnSync with argument arrays.
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* Prevents shell injection by avoiding string interpolation in shell commands.
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*
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* @param cmd - The command to execute
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* @param args - Array of arguments to pass to the command
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* @param options - Optional configuration (cwd, encoding, onError)
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* @returns The trimmed stdout output
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* @throws Error if command fails and no onError handler is provided
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*/
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export function $(cmd: string, args: string[], options?: ShellOptions): string {
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const encoding = options?.encoding ?? "utf-8";
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// CRITICAL: use "ignore" for stdin instead of "inherit" to avoid breaking MCP transport
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// when running inside an MCP server, stdin is used for JSON-RPC protocol
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const result = spawnSync(cmd, args, {
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stdio: ["ignore", "pipe", "pipe"],
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encoding,
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cwd: options?.cwd,
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});
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const stdout = result.stdout ?? "";
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const stderr = result.stderr ?? "";
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// Write output to process streams so it behaves like stdio: "inherit"
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// CRITICAL: when running inside an MCP server, stdout is used for JSON-RPC protocol
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// so we must write to stderr instead to avoid corrupting the protocol
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// Only log if log option is not explicitly set to false
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if (options?.log !== false) {
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// if stdout is a TTY, it's safe to write to it; otherwise it's likely a pipe used for JSON-RPC
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const canWriteToStdout = process.stdout.isTTY === true;
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if (stdout) {
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if (canWriteToStdout) {
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process.stdout.write(stdout);
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} else {
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// stdout is a pipe (MCP context) - write to stderr instead
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process.stderr.write(stdout);
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}
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}
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if (stderr) {
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process.stderr.write(stderr);
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}
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}
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// Handle errors
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if (result.status !== 0) {
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const errorResult = {
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status: result.status ?? -1,
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stdout,
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stderr,
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};
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if (options?.onError) {
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options.onError(errorResult);
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return stdout.trim();
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}
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throw new Error(
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`Command failed with exit code ${errorResult.status}: ${stderr || "Unknown error"}`
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);
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}
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return stdout.trim();
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}
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