bug: Node freezes when using the programmatic API

[Brainy0207]

Context:

• version (md-to-pdf -v): 5.2.0
• platform (Unix, macOS, Windows): Windows
• node version: 19.2.0

Describe the bug:

I have a really simple script:

const { mdToPdf } = require('md-to-pdf');

async function convertAsync() {
  const pdf = await mdToPdf({ content: '# Hello, World' }, {dest: 'output.pdf'});
  console.log(pdf.filename);
}

convertAsync();

If I run this script with node, it logs the filename but freezes after that. I have to press Ctrl+C to get it to return.

It seems that multiple chrome.exe processes are created in the background and node is waiting for them to exit. If I kill these processes with the task manager, node returns.

This seems to be related to #141.
The browser instance created in generateOutput is never closed for the programmatic API:

md-to-pdf/src/lib/generate-output.ts

Lines 36 to 38 in 9f464aa

	if (!browserPromise) {
	browserPromise = puppeteer.launch({ devtools: config.devtools, ...config.launch_options });
	}

And because closeBrowser is not exported to the top level, there seems to be no way to close this browser instance programmaticaly.

[simonhaenisch]

Thanks a lot for the bug report and digging into it, yeah I must have missed that 🙈

I'll see that I get it fixed soon.

[simonhaenisch]

Turns out fixing this is a lot harder than I thought, mainly because of how the library behaves now when running multiple programmatic mdToPdf calls simultaneously (which happens also when running the tests).

There's two options to fix this now:

• fix: "properly" share browser instance in programmatic mode #147: Track the ongoing programmatic conversions and only close the browser once there are no more active ones. This way the browser instance can be shared even between parallel programmatic calls. However it's not a very robust solution that's likely going to break in some edge cases, and that will be hard to fix.
• fix: create one browser instance per programmatic API call #148: Fall back to the previous behavior of one browser instance per programmatic conversion (which of course is slower, creating the browser instance costs about 1 second).

At the cost of performance, I think I'd go with the second solution, and rather fix the performance problem in a better way (I've been planning to change the programmatic API to accept an array input anyway).

[simonhaenisch]

@Brainy0207 should be fixed in 5.2.1, if you could verify that? Thanks!

[Brainy0207]

I ran my test script, no freezing, so I guess it is fixed. Thanks for the quick response.