Function readOutputFromFile

packages/component-sdk/src/runner.ts:214–258

* Read component output from the mounted output file. * If file doesn't exist, falls back to stdout parsing for backwards compatibility. * * @param filePath Path to the output file * @param stdout Captured stdout as fallback for legacy components * @param context Execution context for logging

(
  filePath: string,
  stdout: string,
  context: ExecutionContext
)

 * @param context Execution context for logging
 */
async function readOutputFromFile<O>(
  filePath: string,
  stdout: string,
  context: ExecutionContext
): Promise<O> {
  // First, try to read from the output file (preferred method)
  try {
    await access(filePath, constants.R_OK);
    const content = await readFile(filePath, 'utf8');
    const output = JSON.parse(content.trim());
    context.logger.info(`[Docker] Read output from file (${content.length} bytes)`);
    return output as O;
  } catch (error) {
    if ((error as NodeJS.ErrnoException).code !== 'ENOENT') {
      if (error instanceof SyntaxError) {
        context.logger.error(`[Docker] Failed to parse output JSON: ${error.message}`);
        throw new ValidationError(`Failed to parse container output as JSON: ${error.message}`, {
          cause: error,
        });
      }
      throw error;
    }
    // File not found - fall through to stdout fallback
  }

  // Fallback: Use stdout (for backwards compatibility with legacy components)
  // This allows components that just write to stdout to continue working.
  if (stdout.trim().length > 0) {
    context.logger.info(`[Docker] No output file found, using stdout fallback (${stdout.length} bytes)`);

    // Try to parse stdout as JSON
    try {
      const output = JSON.parse(stdout.trim());
      return output as O;
    } catch {
      // Not JSON - return raw string as output
      // This handles components like subfinder that output plain text
      return stdout.trim() as unknown as O;
    }
  }

  // No output file and no stdout - return empty object
  context.logger.warn('[Docker] No output file or stdout, returning empty result');
  return {} as O;
}

/**
 * Run Docker container with standard I/O.