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Codecov Report

Merging #366 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #366      +/-   ##
==========================================
+ Coverage   96.85%   96.87%   +0.02%     
==========================================
  Files           7        7              
  Lines         254      256       +2     
==========================================
+ Hits          246      248       +2     
  Misses          8        8

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Codecov Report

Merging #366 into master will increase coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #366      +/-   ##
==========================================
+ Coverage   96.85%   96.89%   +0.04%     
==========================================
  Files           7        7              
  Lines         254      258       +4     
==========================================
+ Hits          246      250       +4     
  Misses          8        8

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We need fix it webpack first https://github.com/webpack/webpack/blob/b934e26da8b65bdf36b3c71141d0c2d8397d9f44/package.json#L22

https://github.com/webpack/webpack/blob/8a7597aa6eb2eef66a8f9db3a0c49bcb96022a94/lib/MemoryOutputFileSystem.js

Also can you provide example where

I ran into issues adding my own server-side-rendering middleware into webpack-dev-server that needed to require files from the outputFileSystem. Doing this with memory-fs was difficult, time consuming and seemed not to work very reliably. My alternative was to write to disk, which means 30 second re-builds.

Original comment moved here: https://gist.github.com/heygrady/ae6ec0d725c6c68974802ba5d8328617

difficult, time consuming and seemed not to work very reliably.

This is what I meant:

1. In order to import a file from memory-fs you need to use require-from-string
2. When you use require-from-string you can't use code-splitting
3. When you use require-from-string you can't use node-externals (sometimes)
4. When you read from a buffer, everything becomes async
5. Using fs-monkey with memfs and unionfs would side-step all of those problems.

// importFromMemoryFs.js
const { promisify } = require('util')
const requireFromString = require('require-from-string')

let cache = {}

const importFromMemoryFs = async (stats, pathname) => {
  const { compilation, hash } = stats
  const { outputFileSystem } = compilation.compiler
  if (cache[hash] && cache[hash][pathname]) {
    return cache[hash][pathname]
  } else if (!cache[hash]) {
    cache = { [hash]: {} }
  }
  const readFileAsync = promisify(outputFileSystem.readFile.bind(outputFileSystem))
  try {
    const buffer = await readFileAsync(pathname, 'utf8')
    const source = buffer.toString()
    const module = requireFromString(source, pathname)
    cache[hash][pathname] = module
    return module
  } catch (error) {
    console.error(error)
  }
}

module.exports = importFromMemoryFs

In my project I'm using webpack-dev-server with server-side-rendering. I was able to get it all working roughly as described here.

// ssr-dev-middleware.js
const path = require('path')
const { wrap } = require('async-middleware')

const importFromMemoryFs = './importFromMemoryFs'

const pathToMain = path.join(__dirname, '..', 'dist', 'server', 'main.js')

module.exports = wrap(async (req, res, next) => {
  const stats = res.locals.webpackStats.stats[1]
  const middleware = await importFromMemoryFs(stats, pathToMain)
  middleware(req, res, () => undefined)
})

streamich/memfs#325 (comment)

I created a fork of memory-fs and tried to replace it with Volume. It's mostly working but some tests are failing. Most of the test failures are related to streams.

There are also some failures related to windows-style paths. I think those might be due to memory-fs using a normalize function on all paths and I didn't wrap the memfs methods to do that.

I'm exploring easy ways to make memory-fs API-compliant to work with webpack-dev-server.

https://github.com/heygrady/memory-fs/tree/memfs

Update

webpack/memory-fs#66

I was able to get every test passing except for the tests with win32 paths starting with C:\. It appears that memfs doesn't handle those.

Some differences:

• memfs streams behave like fs does. This causes some tests to fail where memory-fs streams were non-standard.
• memfs has a concept of "relative" paths that uses process.cwd (similar to fs). This causes some tests to fail where memory-fs normally throws on relative paths.
• memfs does not handle win32 paths starting with C:\ (when you are on a posix machine).

Switching to memfs would probably be blocked by the difference in win32 support. I might've overlooked something obvious but the memory-fs tests with paths starting with C:\ totally failed with memfs.

This is nice PR but I got far better solution I believe. #370

@hinell yep, #370 better

If somebody have problem with memory-fs please open issue

@hinell yep, #370 better

If somebody have problem with memory-fs please open issue

I am currently having issues with maxing out memory, I've written my files to disk and that is not helping

@laynef It's better to open a separate issue on that. It would be also nice to elaborate it with details. So far everything it worked smoothly for me.

You can configure fs using options, maybe we revisit default memory fs in future, no need right now

Anyway thank you for the PR