From f03c7fb8d4e5fa75962f41b821b17e5ef8154c96 Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Thu, 22 Dec 2022 19:51:11 +0100
Subject: [PATCH] nixos/version: Only warn about unset stateVersion if used

If a configuration does not use services that depend on the
stateVersion, it does not need to be set.

This provides an incentive for services not to rely on
stateVersion, and not to burden users with this.
---
 nixos/modules/misc/version.nix            | 14 ++++++--------
 nixos/modules/services/matrix/synapse.nix |  6 ++++++
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/nixos/modules/misc/version.nix b/nixos/modules/misc/version.nix
index b3cdaf5568d4..1067b21a22b0 100644
--- a/nixos/modules/misc/version.nix
+++ b/nixos/modules/misc/version.nix
@@ -89,6 +89,12 @@ in
 
     stateVersion = mkOption {
       type = types.str;
+      # TODO Remove this and drop the default of the option so people are forced to set it.
+      # Doing this also means fixing the comment in nixos/modules/testing/test-instrumentation.nix
+      apply = v:
+        lib.warnIf (options.system.stateVersion.highestPrio == (lib.mkOptionDefault { }).priority)
+          "system.stateVersion is not set, defaulting to ${v}. Read why this matters on https://nixos.org/manual/nixos/stable/options.html#opt-system.stateVersion."
+          v;
       default = cfg.release;
       defaultText = literalExpression "config.${opt.release}";
       description = lib.mdDoc ''
@@ -149,14 +155,6 @@ in
       "os-release".text = attrsToText osReleaseContents;
     };
 
-    # We have to use `warnings` because when warning in the default of the option
-    # the warning would also be shown when building the manual since the manual
-    # has to evaluate the default.
-    #
-    # TODO Remove this and drop the default of the option so people are forced to set it.
-    # Doing this also means fixing the comment in nixos/modules/testing/test-instrumentation.nix
-    warnings = lib.optional (options.system.stateVersion.highestPrio == (lib.mkOptionDefault { }).priority)
-      "system.stateVersion is not set, defaulting to ${config.system.stateVersion}. Read why this matters on https://nixos.org/manual/nixos/stable/options.html#opt-system.stateVersion.";
   };
 
   # uses version info nixpkgs, which requires a full nixpkgs path
diff --git a/nixos/modules/services/matrix/synapse.nix b/nixos/modules/services/matrix/synapse.nix
index b9b581acb34a..3087d879b9d2 100644
--- a/nixos/modules/services/matrix/synapse.nix
+++ b/nixos/modules/services/matrix/synapse.nix
@@ -507,6 +507,12 @@ in {
                 sqlite3 = null;
                 psycopg2 = "matrix-synapse";
               }.${cfg.settings.database.name};
+              defaultText = lib.literalExpression ''
+                {
+                  sqlite3 = null;
+                  psycopg2 = "matrix-synapse";
+                }.''${cfg.settings.database.name};
+              '';
               description = lib.mdDoc ''
                 Username to connect with psycopg2, set to null
                 when using sqlite3.