nix-shell-paths-hypothesis.nix

with import <nixpkgs> {};
with pkgs.python27Packages;

##
# Hypothesis: The paths from build-sandbox-paths in /etc/nix/nix.conf
# always get added to the PATH when running nix-shell.
#
# Experiment:
#
# Step 1: Produce a file containing your build-sandbox-paths:
#         `awk '$1=="build-sandbox-paths"{
#            for (n=3;n<=NF;n++) {
#              sub(/[^=]*=/, "", $n);
#              print $n;
#            }
#          }' /etc/nix/nix.conf > ~/build-sandbox-paths.txt`
#
# Step 2: Output your PATH in a user environment
#         outside of nix-shell, like so:
#         `echo "${PATH//:/$'\n'}" > ~/normal-paths.txt`
#
# Step 3: Verify that the build-sandbox-paths are not
#         in that PATH.
#         `grep -xoFf ~/build-sandbox-paths.txt ~/normal-paths.txt`
#         (The output should be empty.)
#
# Step 4: Enter a very simple nix-shell, using this file as default.nix
#
# Step 5: Output your PATH inside the nix-shell:
#         `echo "${PATH//:/$'\n'}" > ~/nix-shell-paths.txt`
#
# Step 6: Exit the nix-shell
#
# Step 7: Verify that the build-sandbox-paths are
#         in the nix-shell-paths:
#         `grep -xoFf ~/build-sandbox-paths.txt ~/nix-shell-paths.txt`
#
# Analysis: If the output of the command in step 7 contains all the build-sandbox-paths
#           then the hypothesis is not disproven.
#
#           If the output of the command in step 7 contains anything else, then the
#           hypothesis is disproven.
#
#           But if the output of the command in step 7 is not empty, then further analysis
#           is needed.

stdenv.mkDerivation {
  name = "test";
  buildInputs = [];
}