Chrome Version       : Version 71.0.3542.0 (Developer Build) (64-bit) 
URLs (if applicable) : N/A
Other browsers tested: N/A

The --disk-cache-dir option only works in headful mode, not in headless mode. Even if you use --user-data-dir, the "Cache" directory is not created. This is problematic if you want to use headless Chrome for web crawling or large website, e.g. for SEO analysis.

What steps will reproduce the problem?

Run the following code in Node.js with Puppeteer:

const puppeteer = require('puppeteer');
const rimraf = require('rimraf');
const childProcess = require('child_process');

const showDir = (path) => {
    try {
        childProcess.execSync(`find ${path} -type f`, { stdio: [0, 1, 2] });
    } catch (e) {
        console.error(`Command failed: ${e}`);
    }
};

(async () => {
    // Test in HEADFUL mode
    rimraf.sync('./cache1');
    const browser1 = await puppeteer.launch({
        args: ['--disk-cache-dir=./cache1'],
        headless: false,
    });
    const page1 = await browser1.newPage();
    console.log('\nHEADFUL BROWSER (BEFORE LOAD):');
    showDir('./cache1');
    await page1.goto('https://www.wikipedia.org');
    console.log('\nHEADFUL BROWSER (AFTER LOAD):');
    showDir('./cache1');
    await browser1.close();

    // Test in HEADLESS mode
    rimraf.sync('./cache2');
    const browser2 = await puppeteer.launch({
        args: ['--disk-cache-dir=./cache2'],
        headless: true,
    });
    const page2 = await browser2.newPage();
    console.log('\nHEADLESS BROWSER (BEFORE LOAD):');
    showDir('./cache2');
    await page2.goto('https://www.wikipedia.org');
    console.log('\nHEADLESS BROWSER (AFTER LOAD):');
    showDir('./cache2');
    await browser2.close();
})();


What is the expected result?

Both headless and headful browser should create and use a directory with disk cache data.

What happens instead?

The disk cache directory is only created in headful mode. The above script prints the following info:

HEADFUL BROWSER (BEFORE LOAD):
./cache1/Default/Cache/index
./cache1/Default/Cache/index-dir/the-real-index

HEADFUL BROWSER (AFTER LOAD):
./cache1/Default/Cache/01e4be952e168d09_0
./cache1/Default/Cache/01e4be952e168d09_1
./cache1/Default/Cache/1069d28c82a80b2b_0
./cache1/Default/Cache/335013cf3c4ddcdc_0
./cache1/Default/Cache/3a8cf1a5b9c24c08_0
./cache1/Default/Cache/40d117288ba98572_0
./cache1/Default/Cache/58c17ba051c7f219_0
./cache1/Default/Cache/74aea27da05a7b9c_0
./cache1/Default/Cache/c5c3241e7f822146_0
./cache1/Default/Cache/f19b3fc2ab4ce672_0
./cache1/Default/Cache/index
./cache1/Default/Cache/index-dir/the-real-index

HEADLESS BROWSER (BEFORE LOAD):
find: ./cache2: No such file or directory
Command failed: Error: Command failed: find ./cache2 -type f

HEADLESS BROWSER (AFTER LOAD):
find: ./cache2: No such file or directory
Command failed: Error: Command failed: find ./cache2 -type f