Function stopTracingAndAppendOutput

src/tools/performance.ts:184–233

(
  page: ContextPage,
  response: Response,
  context: Context,
  filePath?: string,
)

});

async function stopTracingAndAppendOutput(
  page: ContextPage,
  response: Response,
  context: Context,
  filePath?: string,
): Promise<void> {
  try {
    const traceEventsBuffer = await page.pptrPage.tracing.stop();
    if (filePath && traceEventsBuffer) {
      let dataToWrite: Uint8Array = traceEventsBuffer;
      if (filePath.endsWith('.gz')) {
        dataToWrite = await new Promise((resolve, reject) => {
          zlib.gzip(traceEventsBuffer, (error, result) => {
            if (error) {
              reject(error);
            } else {
              resolve(result);
            }
          });
        });
      }
      const file = await context.saveFile(
        dataToWrite,
        filePath,
        filePath.endsWith('.gz') ? '.json.gz' : '.json',
      );
      response.appendResponseLine(
        `The raw trace data was saved to ${file.filename}.`,
      );
    }
    const result = await parseRawTraceBuffer(traceEventsBuffer, {
      cpuThrottling: page.cpuThrottlingRate,
      networkThrottling: page.networkConditions ?? undefined,
    });
    response.appendResponseLine('The performance trace has been stopped.');
    if (traceResultIsSuccess(result)) {
      if (context.isCruxEnabled()) {
        await populateCruxData(result);
      }
      context.storeTraceRecording(result);
      response.attachTraceSummary(result);
    } else {
      throw new Error(
        `There was an unexpected error parsing the trace: ${result.error}`,
      );
    }
  } finally {
    context.setIsRunningPerformanceTrace(false);
  }
}

/** We tell CrUXManager to fetch data so it's available when DevTools.PerformanceTraceFormatter is invoked */
async function populateCruxData(result: TraceResult): Promise<void> {