devshells.current.add-gc-root

#!/usr/bin/env bash

# Stops the dependencies of a devshell from being garbage
# collected. If we don't do this then running 'nix develop' will
# re-download a lot of data every time 'nix store gc' is called.

if [ -z ${DEVSHELL_NAME+x} ]; then
    echo "Must be called from within 'nix develop'"
    exit 1
fi

# Finds the directory that this script was written in and puts it in
# $SCRIPT_PATH. See https://stackoverflow.com/a/179231.

pushd . > '/dev/null';
SCRIPT_PATH="${BASH_SOURCE[0]:-$0}";

while [ -h "$SCRIPT_PATH" ];
do
    cd "$( dirname -- "$SCRIPT_PATH"; )";
    SCRIPT_PATH="$( readlink -f -- "$SCRIPT_PATH"; )";
done

cd "$( dirname -- "$SCRIPT_PATH"; )" > '/dev/null';
SCRIPT_PATH="$( pwd; )";
popd  > '/dev/null';

# Add GC roots for devshell inputs. See
# https://github.com/ruuda/dotfiles/blob/master/zsh/.zshrc. The
# variable 'DEVSHELL_NAME' is defined in flake.nix.

GC_ROOT="${SCRIPT_PATH}/.devshells/${DEVSHELL_NAME}"
DEVSHELL_FLAKE_OUTPUT=".#devShells.x86_64-linux.${DEVSHELL_NAME}"
DEVSHELL_STOREPATH=$(nix build --no-link --print-out-paths "${DEVSHELL_FLAKE_OUTPUT}")
nix --offline flake archive --dry-run --json \
    | jq --raw-output '.. | .path? | select(. != null)' \
    | xargs --max-procs=1 \
            nix-store --add-root "${GC_ROOT}" --indirect --realise "${DEVSHELL_STOREPATH}" \
            > /dev/null