Do not rely on Node.js internals

[mcollina]

This restores compatibility with Node 9 by lifting the code from Node 8.9.4 and copying and pasting it here. This should have been the approach from the very beginning, because vinyl-fs is creating its own WriteStream that has very little in common with the one from Node core.

Unfortunately, pulling functions from a prototype and attaching them to a non-related one is a very dangerous technique: as you can imagine a function attached to a prototype relies on the state that is created by the relative constructor. These are implementation details, and they can surely change across major versions.

As a side note, this was likely broken by nodejs/node#15407 and nodejs/node#18002.

Fixes #295

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The actual logic can probably be simplified, because vinyl-fs WriteStream implementation is different than the one in Node core.

[phated]

@mcollina thanks! It looks like these changes devastated Windows. Any ideas?

[mcollina]

@phated I've just checked on a Windows box, and it's failing even on master with Node 8 and 6. It's not related (but should probably be fixed anyway in another PR).

[phated]

@mcollina not sure about that https://ci.appveyor.com/project/gulpjs/vinyl-fs/build/735 - we've had successful builds for quite some time.

[mcollina]

@phated these are what I am getting (more or less all of the same, ENOENT on files):

  24) symlink stream (windows) options can disable junctions for a directory (as a function):
     Uncaught Error: ENOENT: no such file or directory, stat 'C:\Users\Matteo\Repositories\vinyl-fs\test\out-fixtures\foo'
      at Error (native)
      at Object.fs.statSync (fs.js:1009:11)
      at Object.statSync (node_modules\graceful-fs\polyfills.js:297:22)
      at assert (test\symlink.js:395:22)
      at ConcatStream.<anonymous> (node_modules\concat-stream\index.js:36:43)
      at finishMaybe (node_modules\readable-stream\lib\_stream_writable.js:607:14)
      at endWritable (node_modules\readable-stream\lib\_stream_writable.js:615:3)
      at ConcatStream.Writable.end (node_modules\readable-stream\lib\_stream_writable.js:571:41)
      at ConcatStream.Writable._destroy (node_modules\readable-stream\lib\_stream_writable.js:662:8)
      at ConcatStream.destroy (node_modules\readable-stream\lib\internal\streams\destroy.js:36:8)
      at node_modules\mississippi\node_modules\pump\index.js:43:45
      at call (node_modules\mississippi\node_modules\pump\index.js:50:3)
      at Array.forEach (native)
      at node_modules\mississippi\node_modules\pump\index.js:70:25
      at f (node_modules\once\once.js:25:25)
      at Pumpify.<anonymous> (node_modules\mississippi\node_modules\pump\index.js:29:21)
      at Pumpify.f (node_modules\once\once.js:25:25)
      at Pumpify.onerror (node_modules\end-of-stream\index.js:43:12)
      at Pumpify.Duplexify._destroy (node_modules\duplexify\index.js:195:15)
      at node_modules\duplexify\index.js:179:10
      at _combinedTickCallback (internal/process/next_tick.js:73:7)
      at process._tickCallback (internal/process/next_tick.js:104:9)

(this is node 6 on master)

Maybe a dependency changed and broke things?

[mcollina]

Can you trigger a build on master?

[phated]

@mcollina done and still passing on Windows: https://ci.appveyor.com/project/gulpjs/vinyl-fs/build/738

[mcollina]

@phated the test suite on master fails on Windows Home Edition. I guess it's due to the permissions required to create symlinks (I stumbled upon that in the past, and it seems the case).

I ended up removing FlushWriteStream and using Writable directly (since readable-stream 2.3.0 it offer _final). The alternative is to copy the methods from Node 6 instead, those should work. I went for Writable, because it removes a dependency.
Let me know if you prefer the Node 6 approach.

[phated]

I ended up removing FlushWriteStream and using Writable directly (since readable-stream 2.3.0 it offer _final)

Oh wow, so _final is always called before the defined .close method is called (since that closes the file descriptor)? That's a great additional API!

[mcollina]

Oh wow, so _final is always called before the defined .close method is called (since that closes the file descriptor)? That's a great additional API!

Yes! _final is called before the streams emits 'finish', it was such a useful feature that we added it in Node 8 (readable-stream@2.3.x).

[phated]

This was rebased and merged as 167d8ff and 62d1969 - publishing as 3.0.2 once CI completes.

Thanks again!