Function expandEnvRefs

src/mcp/manager.ts:19–55

(config: MCPServerConfig, serverName: string)

 * the input is not mutated.
 */
export function expandEnvRefs(config: MCPServerConfig, serverName: string): MCPServerConfig {
  const missing = new Set<string>();
  const expand = (s: string): string =>
    s.replace(/\$\{([A-Za-z_][A-Za-z0-9_]*)\}/g, (_m, varName: string) => {
      const v = process.env[varName];
      if (v === undefined || v === '') { missing.add(varName); return ''; }
      return v;
    });

  const out: MCPServerConfig = { ...config };

  if (config.args) out.args = config.args.map(a => (typeof a === 'string' ? expand(a) : a));
  if (config.url) out.url = expand(config.url);
  if (config.env) {
    const env: Record<string, string> = {};
    for (const [k, val] of Object.entries(config.env)) {
      env[k] = typeof val === 'string' ? expand(val) : (val as any);
    }
    out.env = env;
  }
  if (config.headers) {
    const headers: Record<string, string> = {};
    for (const [k, val] of Object.entries(config.headers)) {
      headers[k] = typeof val === 'string' ? expand(val) : (val as any);
    }
    out.headers = headers;
  }

  if (missing.size > 0) {
    logger.warn(
      `MCP server '${serverName}': unset env var(s) ${[...missing].join(', ')} — ` +
      `referenced in config but not exported. The server will likely fail to authenticate. ` +
      `Export them (e.g. \`export ${[...missing][0]}=...\`) or re-add with --inline.`,
    );
  }
  return out;
}

/**
 * MCPManager: lifecycle owner for all configured MCP servers.