init project setup

1 files changed, 154 insertions, 0 deletions

diff --git a/.envrc b/.envrc
new file mode 100644
index 0000000..75fb474
--- /dev/null
+++ b/.envrc
@@ -0,0 +1,154 @@
+# Load environment variables from `nix-shell` and export it out.
+#
+# Usage: use_nix [-s <nix-expression>] [-w <path>] [-w <path>] ...
+#   -s nix-expression: The nix expression to use for building the shell environment.
+#   -w path: watch a file for changes. It can be specified multiple times. The
+#      shell specified with -s is automatically watched.
+#
+#   If no nix-expression were given with -s, it will attempt to find and load
+#   the shell using the following files in order: shell.nix and default.nix.
+#
+# Example:
+#   -  use_nix
+#   -  use_nix -s shell.nix -w .nixpkgs-version.json
+#
+# The dependencies pulled by nix-shell are added to Nix's garbage collector
+# roots, such that the environment remains persistent.
+#
+# Nix-shell is invoked only once per environment, and the output is cached for
+# better performance. If any of the watched files change, then the environment
+# is rebuilt.
+#
+# To remove old environments, and allow the GC to collect their dependencies:
+# rm -f .direnv
+#
+use_nix() {
+	if ! validate_version; then
+		echo "This .envrc requires direnv version 2.18.2 or above."
+		exit 1
+	fi
+
+	# define all local variables
+	local shell
+	local files_to_watch=()
+
+	local opt OPTARG OPTIND # define vars used by getopts locally
+	while getopts ":n:s:w:" opt; do
+		case "${opt}" in
+			s)
+				shell="${OPTARG}"
+				files_to_watch=("${files_to_watch[@]}" "${shell}")
+				;;
+			w)
+				files_to_watch=("${files_to_watch[@]}" "${OPTARG}")
+				;;
+			:)
+				fail "Invalid option: $OPTARG requires an argument"
+				;;
+			\?)
+				fail "Invalid option: $OPTARG"
+				;;
+		esac
+	done
+	shift $((OPTIND -1))
+
+	if [[ -z "${shell}" ]]; then
+		if [[ -f shell.nix ]]; then
+			shell=shell.nix
+			files_to_watch=("${files_to_watch[@]}" shell.nix)
+		elif [[ -f default.nix ]]; then
+			shell=default.nix
+			files_to_watch=("${files_to_watch[@]}" default.nix)
+		else
+			fail "ERR: no shell was given"
+		fi
+	fi
+
+	local f
+	for f in "${files_to_watch[@]}"; do
+		if ! [[ -f "${f}" ]]; then
+			fail "cannot watch file ${f} because it does not exist"
+		fi
+	done
+
+	# compute the hash of all the files that makes up the development environment
+	local env_hash="$(hash_contents "${files_to_watch[@]}")"
+
+	# define the paths
+	local dir="$(direnv_layout_dir)"
+	local wd="${dir}/wd-${env_hash}"
+	local drv="${wd}/env.drv"
+	local dump="${wd}/dump.env"
+
+	# Generate the environment if we do not have one generated already.
+	if [[ ! -f "${drv}" ]]; then
+		mkdir -p "${wd}"
+
+		log_status "use nix: deriving new environment"
+		IN_NIX_SHELL=1 nix-instantiate --add-root "${drv}" --indirect "${shell}" > /dev/null
+		nix-store -r $(nix-store --query --references "${drv}") --add-root "${wd}/dep" --indirect > /dev/null
+		if [[ "${?}" -ne 0 ]] || [[ ! -f "${drv}" ]]; then
+			rm -rf "${wd}"
+			fail "use nix: was not able to derive the new environment. Please run 'direnv reload' to try again."
+		fi
+
+		log_status "use nix: updating cache"
+		nix-shell --pure "${drv}" --show-trace --run "$(join_args "$direnv" dump bash)" > "${dump}"
+		if [[ "${?}" -ne 0 ]] || [[ ! -f "${dump}" ]] || ! grep -q IN_NIX_SHELL "${dump}"; then
+			rm -rf "${wd}"
+			fail "use nix: was not able to update the cache of the environment. Please run 'direnv reload' to try again."
+		fi
+	fi
+
+	# evaluate the dump created by nix-shell earlier, but have to merge the PATH
+	# with the current PATH
+	# NOTE: we eval the dump here as opposed to direnv_load it because we don't
+	# want to persist environment variables coming from the shell at the time of
+	# the dump. See https://github.com/direnv/direnv/issues/405 for context.
+	local path_backup="${PATH}"
+	eval $(cat "${dump}")
+	export PATH="${PATH}:${path_backup}"
+
+	# cleanup the environment of variables that are not requried, or are causing issues.
+	unset shellHook  # when shellHook is present, then any nix-shell'd script will execute it!
+
+	# watch all the files we were asked to watch for the environment
+	for f in "${files_to_watch[@]}"; do
+		watch_file "${f}"
+	done
+}
+
+fail() {
+	log_error "${@}"
+	exit 1
+}
+
+hash_contents() {
+	if has md5sum; then
+		cat "${@}" | md5sum | cut -c -32
+	elif has md5; then
+		cat "${@}" | md5 -q
+	fi
+}
+
+hash_file() {
+	if has md5sum; then
+		md5sum "${@}" | cut -c -32
+	elif has md5; then
+		md5 -q "${@}"
+	fi
+}
+
+validate_version() {
+	local version="$("${direnv}" version)"
+	local major="$(echo "${version}" | cut -d. -f1)"
+	local minor="$(echo "${version}" | cut -d. -f2)"
+	local patch="$(echo "${version}" | cut -d. -f3)"
+
+	if [[ "${major}" -gt 2 ]]; then return 0; fi
+	if [[ "${major}" -eq 2 ]] && [[ "${minor}" -gt 18 ]]; then return 0; fi
+	if [[ "${major}" -eq 2 ]] && [[ "${minor}" -eq 18 ]] && [[ "${patch}" -ge 2 ]]; then return 0; fi
+	return 1
+}
+
+use_nix -s shell.nix -w .nixpkgs-version.json