depot/third_party/tvl/tools/nixery/popcount/README.md

popcount

This script is used to count the popularity for each package in nixpkgs, by determining how many other packages depend on it.

It skips over all packages that fail to build, are not cached or are unfree - but these omissions do not meaningfully affect the statistics.

It currently does not evaluate nested attribute sets (such as haskellPackages).

Usage

1. Generate a list of all top-level attributes in nixpkgs:

   nix eval '(with builtins; toJSON (attrNames (import <nixpkgs> {})))' | jq -r | jq > all-top-level.json
   

2. Run ./popcount > all-runtime-deps.txt

3. Collect and count the results with the following magic incantation:

   cat all-runtime-deps.txt \
     | sed -r 's|/nix/store/[a-z0-9]+-||g' \
     | sort \
     | uniq -c \
     | sort -n -r \
     | awk '{ print "{\"" $2 "\":" $1 "}"}' \
     | jq -c -s '. | add | with_entries(select(.value > 1))' \
     > your-output-file
   

   In essence, this will trim Nix's store paths and hashes from the output, count the occurences of each package and return the output as JSON. All packages that have no references other than themselves are removed from the output.