src/server/middleware/symbolicateMiddleware.js
async function createSourceMapConsumer(compiler: Compiler, url: string) {
  const response = await fetch(url);
  const sourceMap = await response.text();

  // we stop here if we couldn't find that map
  if (!sourceMap) {
    logger.warn(messages.sourceMapFileNotFound());
    return null;
  }

  // feed the raw source map into our consumer
  try {
    return new SourceMapConsumer(sourceMap);
  } catch (err) {
    logger.error(messages.sourceMapInvalidFormat());
    return null;
  }
}
async function createSourceMapConsumer(compiler: Compiler, url: string) {
  const response = await fetch(url);
  const sourceMap = await response.text();

  // we stop here if we couldn't find that map
  if (!sourceMap) {
    logger.warn(messages.sourceMapFileNotFound());
    return null;
  }

  // feed the raw source map into our consumer
  try {
    return new SourceMapConsumer(sourceMap);
  } catch (err) {
    logger.error(messages.sourceMapInvalidFormat());
    return null;
  }
}
Creates a SourceMapConsumer so we can query it.