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Fix "illegal operation on a directory, realpath" on RAM Disk #229

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14 changes: 13 additions & 1 deletion lib/async.js
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,19 @@ var nodeModulesPaths = require('./node-modules-paths');
var normalizeOptions = require('./normalize-options');
var isCore = require('is-core-module');

var realpathFS = fs.realpath && typeof fs.realpath.native === 'function' ? fs.realpath.native : fs.realpath;
function realpathFS(path, callback) {
if (typeof fs.realpath.native === 'function') {
fs.realpath.native(path, function (realpathErr, realPath) {
if (realpathErr && realpathErr.errno === -4068) {
fs.realpath(path, callback);
} else {
return callback(realpathErr, realPath);
}
});
Comment on lines +10 to +16
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this means we pay a performance cost every time. is this necessary, or on a given system where it fails, will it always fail?

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This code is designated for the postcss-import on RAM Disk. This means the I/O speed is significantly improved. The production build of my Angular project takes 60-120 secs with fs.realpath.native() on my 2TB Seagate FireCuda SSHD but it only takes ~60 secs on RAM Disk mounted by imDisk with fs.realpath() (where fs.realpath.native() is illegal operation). So in general, no performance costs are paid.

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I'm not sure how that's possible - this is always calling realpath.native, and when it errors, is adding the cost of calling realpath.

(to be clear, I have no idea what imDisk is, and the last time I heard anything about RAM Disks was in the late 1990s)

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imDisk is a software to create a virtual disk using RAM on Windows: https://imdisk.en.lo4d.com/windows

The cost of calling is the trade-off for I/O speed and it only adding the call on illegal operation error.

You can clone this repository using Windows on both RAM Disk created by imDisk and your HDD/SSHD/SSD https://github.com/scttcper/ngx-toastr. After the clone, run npm i && npm start. On RAM Disk, the server will fail and you will get
image

The cause is from postcss-import using this repository to resolve the imported files from node_modules in src/style.scss. So if you alter ./node_modules/resolve/lib/async.js, the error is gone.

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I'm concerned about:

  1. adding a fix without a regression test, because there's no protection from breaking it again
  2. adding a complicated fix that might slow down the majority case to service a very niche edge case

} else {
fs.realpath(path, callback);
}
}

var defaultIsFile = function isFile(file, cb) {
fs.stat(file, function (err, stat) {
Expand Down
14 changes: 13 additions & 1 deletion lib/sync.js
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,19 @@ var caller = require('./caller');
var nodeModulesPaths = require('./node-modules-paths');
var normalizeOptions = require('./normalize-options');

var realpathFS = fs.realpathSync && typeof fs.realpathSync.native === 'function' ? fs.realpathSync.native : fs.realpathSync;
function realpathFS(path) {
if (typeof fs.realpathSync.native === 'function') {
try {
return fs.realpathSync.native(path);
} catch (realpathErr) {
if (!realpathErr || realpathErr.errno !== -4068) {
throw realpathErr;
}
}
}

return fs.realpathSync(path);
}

var defaultIsFile = function isFile(file) {
try {
Expand Down