From 3281fb9132c815c9a017e8ecd1e49b91b6cb92ff Mon Sep 17 00:00:00 2001
From: Florian Klink <flokli@flokli.de>
Date: Wed, 20 Mar 2024 15:19:37 +0200
Subject: docs(ops/terraform/deploy-nixos): document inputs and outputs

This documents the input and output format, and also removes some
references to Terraform and evaluating NixOS system configurations.

It can be used to evaluate anything.

Change-Id: I8492cc3e386f89b299469c78e586644ee82a708f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11213
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
---
 ops/terraform/deploy-nixos/main.tf       |  2 +-
 ops/terraform/deploy-nixos/nix-eval.sh   | 34 ++++++++++++++++++++++++++++++++
 ops/terraform/deploy-nixos/nixos-eval.sh | 21 --------------------
 3 files changed, 35 insertions(+), 22 deletions(-)
 create mode 100755 ops/terraform/deploy-nixos/nix-eval.sh
 delete mode 100755 ops/terraform/deploy-nixos/nixos-eval.sh

(limited to 'ops')

diff --git a/ops/terraform/deploy-nixos/main.tf b/ops/terraform/deploy-nixos/main.tf
index 00023fba69..50278b248e 100644
--- a/ops/terraform/deploy-nixos/main.tf
+++ b/ops/terraform/deploy-nixos/main.tf
@@ -53,7 +53,7 @@ variable "triggers" {
 
 # Fetch the derivation hash for the NixOS system.
 data "external" "nixos_system" {
-  program = ["${path.module}/nixos-eval.sh"]
+  program = ["${path.module}/nix-eval.sh"]
 
   query = {
     attrpath   = var.attrpath
diff --git a/ops/terraform/deploy-nixos/nix-eval.sh b/ops/terraform/deploy-nixos/nix-eval.sh
new file mode 100755
index 0000000000..2591da28ae
--- /dev/null
+++ b/ops/terraform/deploy-nixos/nix-eval.sh
@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+
+# SPDX-FileCopyrightText: 2023 The TVL Authors
+#
+# SPDX-License-Identifier: MIT
+set -ueo pipefail
+
+# Evaluates a Nix expression.
+#
+# Receives input parameters as JSON from stdin.
+# It expects a dict with the following keys:
+#
+#  - `attrpath`: the attribute.path pointing to the expression to instantiate.
+#    Required.
+#  - `entrypoint`: the path to the Nix file to invoke.
+#    Optional. If omitted, will shell out to git to determine the repo root,
+#    and Nix will use `default.nix` in there.
+#  - `argstr`: A map containing string keys and values
+#    which are passed to Nix as `--argstr $key $value`
+#    command line args. Optional.
+#
+# jq's @sh format takes care of escaping.
+eval "$(jq -r '@sh "attrpath=\(.attrpath) && entrypoint=\(.entrypoint) && argstr=\((.argstr // {}) | to_entries | map ("--argstr", .key, .value) | join(" "))"')"
+
+# Evaluate the expression.
+[[ -z "$entrypoint" ]] && entrypoint=$(git rev-parse --show-toplevel)
+# shellcheck disable=SC2086,SC2154
+drv=$(nix-instantiate -A "${attrpath}" "${entrypoint}" ${argstr})
+
+# Return a JSON back to stdout.
+# It contains the following keys:
+#
+# - `drv`: the store path of the Derivation that has been instantiated.
+jq -n --arg drv "$drv" '{"drv":$drv}'
diff --git a/ops/terraform/deploy-nixos/nixos-eval.sh b/ops/terraform/deploy-nixos/nixos-eval.sh
deleted file mode 100755
index f206fe7f68..0000000000
--- a/ops/terraform/deploy-nixos/nixos-eval.sh
+++ /dev/null
@@ -1,21 +0,0 @@
-#!/usr/bin/env bash
-
-# SPDX-FileCopyrightText: 2023 The TVL Authors
-#
-# SPDX-License-Identifier: MIT
-
-#
-# Builds a NixOS system configuration at the given attribute path.
-set -ueo pipefail
-
-# Load input variables from Terraform. jq's @sh format takes care of
-# escaping.
-eval "$(jq -r '@sh "attrpath=\(.attrpath) && entrypoint=\(.entrypoint) && argstr=\((.argstr // {}) | to_entries | map ("--argstr", .key, .value) | join(" "))"')"
-
-# Evaluate the system derivation.
-[[ -z "$entrypoint" ]] && entrypoint=$(git rev-parse --show-toplevel)
-# shellcheck disable=SC2086,SC2154
-system_drv=$(nix-instantiate -A "${attrpath}" "${entrypoint}" ${argstr})
-
-# Return system derivation back to Terraform.
-jq -n --arg drv "$system_drv" '{"drv":$drv}'
-- 
cgit 1.4.1