[Nix-dev] Simplify node packages?

[Profpatsch]

On 17-04-25 07:26am, Benno Fünfstück wrote:
> >
> > The most interesting property is, that all dependency trees
> > are linked together with symlinked, so they are cached by nix
> > on a package level:
> > https://github.com/Profpatsch/yarn2nix/blob/master/buildNodePackage.nix#L33
> 
> 
> Does this caching really gain us that much? The disadvantage of doing this
> is that we have to maintain our own scripts for doing it, since upstream
> does not support it.

Depends by who you mean by upstream.

yarn: only the parser could break, but that’s easily fixable
npm: they could change something in how packages work,
but that’s unlikely.

> phase 1: build a directory full of tarballs (just symlink the result of
> fetchurl without unpacking)
> phase 2: let yarn assemble the dependency tree (thus it will deal with
> cyclic dependencies for us)

Right now it takes around 4–5 minutes to unpack the tarballs
for my project with node2nix. That is on every dep change.

> This would only need a feature from upstream to use cached tarballs.

npm uses the following algorithm:
1. resolve dependencies
2. move dependencies as far up the tree as possible to enable sharing
3. unpack the tarballs into the correct dirs
4. link the "bin" files into a .bin directory and the man files

That’s it.
We can skip step 2, because we don’t copy, but symlink
already extracted packages (and filename length is not
a problem on modern ext/btrfs/zfs)
Step 4 becomes trivial once we skip 2.

yarn is really just a 1:1 rewrite of node with lockfiles.
I don’t know why people celebrate it so much,
because it does exactly nothing differently apart from
creating the lockfiles.
Don’t even know why a rewrite was necessary.

Maybe I missed something, but that’s the plan.

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