Async PostCSS Plugin on Windows 10 with too many parsed files (~10k) yields a webpack error (EMFILE: too many open files)

[akehir]

What version of Tailwind CSS are you using?

v3.3.3

What build tool (or framework if it abstracts the build tool) are you using?

    "@angular/cli": "~16.2.3",
    "autoprefixer": "10.4.16",
    "postcss": "8.4.30",
    "tailwindcss": "3.3.3",

What version of Node.js are you using?

For example: v18.18.0

What browser are you using?

N/A

What operating system are you using?

Windows 10, 22H2

Reproduction URL
https://github.com/akehir/tailwindowsbugger

Describe your issue

After upgrading to tailwind 3.3.3 (from 3.3.2) we faced an issue with npm start (or ng serve), with the error EMFILE: too many open files`. From my analysis, the bug is introduced in the PR when postcss was made async ( https://github.com/tailwindlabs/tailwindcss/pull/11548/files#diff-2f0997968f6094158825cb36c24f8b489c2d3f5aa72279d721077e5901280a30L169 ).

Upon reverting the changed lines in the node_modules of the project, I can execute the build successfully (see example of reverted file below).

After parsing ~8k files Windows has the error ``EMFILE: too many open files` which leads to the build failing. Our project has around 10k files to parse, triggering the error.

The reproduction is basically just creating a blank angular repository, adding tailwindcss, and creating 10'000 blank typescript files.

You can get a Windows VM from https://developer.microsoft.com/en-us/windows/downloads/virtual-machines/

In the VM, the reproduction is as follows: 1) install nodejs and clone (download) the project 2) npm i 3) npm start

With that you can trigger the error.

I think, the async code has either to be disabled on windows (keeping the old sync code), or the async code should work in batches of ~1k files. I could create a PR to disable the async part on Windows, if you'd like.

Example error in console:

HookWebpackError: Module build failed (from ./node_modules/postcss-loader/dist/cjs.js):
Error: EMFILE: too many open files, open 'C:\git\tailwindowsbugger\src\files\file-919.ts'

expandTailwindAtRules.js in node modules (adapted to fix the bug).

        } else {
            console.log('Reverting the changes...');
            // console.log(_fs.default);
            let count = 0;
            for (let { file, content, extension } of context.changedContent) {
                let transformer = getTransformer(context.tailwindConfig, extension)
                let extractor = getExtractor(context, extension)
                console.log(`File #${count}`, file);
                count++;
                content = file ? _fs.default.readFileSync(file, 'utf8') : content
                getClassCandidates(transformer(content), extractor, candidates, seen)
            }
            await new Promise((resolve, reject) => {
                resolve("foo");
            });

            // await Promise.all(context.changedContent.map(async ({ file , content , extension  })=>{
            //     let transformer = getTransformer(context.tailwindConfig, extension);
            //     let extractor = getExtractor(context, extension);
            //     content = file ? await _fs.default.promises.readFile(file, "utf8") : content;
            //     console.log(`File #${count}`, file);
            //     count++;
            //     getClassCandidates(transformer(content), extractor, candidates, seen);
            // }));
        }
        

[thecrypticace]

Yeah I think we'll want to batch file reads into groups rather than turn off the async stuff.

Throwing this here so I don't forget: We can test this super easily on macOS by setting a super low hard file open limit by doing ulimit -Hn 256

(I tested it on Windows too though — I've got a Windows machine I game on)

[thecrypticace]

This should be fixed by #12079, and will be available in the next release.

You can try it by using the insiders build (should be available in ~10m or so once it's built and published):

npm install tailwindcss@insiders

[akehir]

Cool thanks a lot, I'll try it out tomorrow!

[akehir]

Can confirm it works with tailwind@insiders in our project, many thanks!