build-node-package.nix takes excessive amount of time

[edolstra]

Issue description

A profile of NIX_COUNT_CALLS=1 nix-env -qa --drv-path on Nixpkgs master shows that build-node-package.nix is the most dominant function during evaluation:

calls to 9295 functions:
    210846 anonymous function at /home/eelco/Dev/nixpkgs-stable/pkgs/development/web/nodejs/build-node-package.nix:314:33
    201017 anonymous function at /home/eelco/Dev/nixpkgs-stable/pkgs/tools/typesetting/tex/texlive-new/combine.nix:31:36
    201017 anonymous function at /home/eelco/Dev/nixpkgs-stable/pkgs/tools/typesetting/tex/texlive-new/combine.nix:31:39
     93926 ‘optional’ at /home/eelco/Dev/nixpkgs-stable/lib/lists.nix:175:14
     93926 ‘optional’ at /home/eelco/Dev/nixpkgs-stable/lib/lists.nix:175:20
...

In fact about 23% of Nixpkgs evaluation time is spent in nodejs stuff.

This is strange because hardly any nodejs packages are included in the output:

$ nix-env -f ~/Dev/nixpkgs -qa --drv-path | grep nodejs | wc -l
14

So it looks like there is some opportunity for optimisation here...

Steps to reproduce

Technical details

• System: 16.03.git.7a41a40M
• Nix version: 1.11.2
• Nixpkgs version: 8a84fc0

[domenkozar]

I wonder, how do you know 23% of time is spent on nodejs stuff?

[edolstra]

Just by disabling node-packages.nix:

diff --git a/pkgs/top-level/node-packages.nix b/pkgs/top-level/node-packages.nix
index d8eb668..3d9cf8d 100644
--- a/pkgs/top-level/node-packages.nix
+++ b/pkgs/top-level/node-packages.nix
@@ -15,7 +15,7 @@
 , ...
 } @ args:

-with stdenv.lib;
+with stdenv.lib; assert false;

 let
   removeDeps = remove: deps: filterAttrs (n: d: all (r: r != d.pkgName) remove) deps;

[domenkozar]

There is some deep magic in pkgs/development/web/nodejs/build-node-package.nix.

So hopefully #16886 will yield #14532

[domenkozar]

@svanderburg how is the new code performance comparing to previous?

[FlorentBecker]

This seems to be fixed (texlive is now at the top of that listing).

[globin]

Yep, looks fine