feat: add channel parameter for puppeteer.launch

[YusukeIwaki]

Add 'channel' parameter for Puppeteer.launch

Resolves #7340

Google Chrome is often used for using puppeteer as a browser automation tool,
We have to specify executablePath in such case. However we can't share the code among Windows/macOS users, because executablePath is different.

microsoft/playwright already introduced the channel parameter for solving this problem.
Let's provide the similar functionality for Puppeteer users.

const puppeteer = require('puppeteer');

puppeteer.launch({ channel: 'chrome-canary', headless: false }).then(async (browser) => {
    const page = await browser.newPage();
    await page.goto('https://github.com/puppeteer');
    await browser.close();
});

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[YusukeIwaki]

@googlebot I signed it!

[jschfflr]

The change looks good to me, thanks for your contribution!
I left some comments and maybe we should also think about whether PUPPETEER_EXECUTABLE_PATH should take precedence over the channel or not.
Let me know what you think!

[YusukeIwaki]

Thank you for your kind review. I considered again about the priority of channel and executablePath.

• [1] executablePath should be ignored when channel is specified
• [2] executablePath should be respected even when channel is specified

[1] is actually adopted in Playwright. This is really simple. I think [1] is better.

The use-case of [2] is like below:
When some users changed the install path of Chrome, channel: chrome fails to detect Chrome. Without modifying the script source code, users can set the install path with PUPPETEER_EXECUTABLE_PATH=/path/to/chrome

However in [2], users can also specify MS Edge as executablePath even when channel: chrome.
If the script developer intends to the script is assumed to work with Chrome, PUPPETEER_EXECUTABLE_PATH=/path/to/msedge is just a source of worry.

This is just my observation but I didn't see the people who change the Chrome install path, and I thought [2] is useful for only a few people. IMO, simplicity is better than considering the edge case.
So I suggedt the spec [1] executablePath should be ignored when channel is specified

[jschfflr]

Looks good to me from a technical point of view now.
But please also update the documentation in docs/api.md to explain the change.

[jschfflr]

Regarding the priority: Let's make them mutually exclusive.
If one of them is specified, the other one can not be set - that way, people don't run into unexpected behaviour.
Can you add an assert for that?

[YusukeIwaki]

Regarding the priority: Let's make them mutually exclusive.
If one of them is specified, the other one can not be set - that way, people don't run into unexpected behaviour.

That's a good idea. I will add assertion for it.

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[YusukeIwaki]

@jschfflr Thank you for your kind review.
Could you re-run GitHub actions? The failed test is caused by flaky testcase.

[jschfflr]

Sure :)

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[YusukeIwaki]

Rebased.

[jschfflr]

The change LGTM now!

[jschfflr]

Your change landed 🎉
Thanks for your contribution @YusukeIwaki!

[noinkling]

Any particular reason this feature only checks Program Files and not also Program Files (x86) on Windows? My Chrome installation is located in the latter. According to this it was the default location until 2020. For installations existing before that point, it seems like the only (non-hacky) way to move it is to uninstall and reinstall.

Playwright appears to look in both (as well as in AppData/Local, which I seem to remember was indeed where the executable lived at one point), if that's any motivation: https://github.com/microsoft/playwright/blob/b6eb917c29b743e8d63004ae7a24974404461198/packages/playwright-core/src/utils/registry.ts#L461