Unable to get multipart/form-data from POST requests with requestInterceptor

Steps to reproduce

Tell us about your environment:

• Puppeteer version: 2.0.0
• Platform / OS version: macOS 10.15 (19A602)
• URLs (if applicable): https://codesandbox.io/s/fervent-http-c24v7 (for the demo)
• Node.js version: v12.13.0

What steps will reproduce the problem?

Please include code that reproduces the issue.

1. Create a form with enctype="multipart/form-data", e.g. https://codesandbox.io/s/fervent-http-c24v7
2. Open the page with puppeteer, add a request interceptor, add a file to the upload input and submit the form.

const puppeteer = require("puppeteer");

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.setRequestInterception(true);

  page.on("request", (interceptedRequest) => {
    if (interceptedRequest.method() === "POST") {
      console.log(interceptedRequest.postData());
    }

    interceptedRequest.continue();
  });

  await page.goto("https://c24v7.codesandbox.io/");
  const input = await page.$("#file_input");

  // a simple txt file with little just some dummy text
  await input.uploadFile("./file.txt");
  await page.click("#submit");
  
  await browser.close();
})().catch(console.error);

What is the expected result? According to me, the multipart/form-data should be available inside the request interceptor (requestInterceptor.postData()).

What happens instead? The requestInterceptor.postData() is undefined. Interestingly, when using puppeteer-firefox, this very same code works properly and the postData() is available inside the requestInterceptor.

[ivansieder]

I’ve switched to Firefox @rgoldstein01

[stale[bot]]

We are closing this issue. If the issue still persists in the latest version of Puppeteer, please reopen the issue and update the description. We will try our best to accomodate it!