From d3caafc32f68040ba90848d73555c8ed304af02d Mon Sep 17 00:00:00 2001
From: Wolfgang Walther <walther@technowledgy.de>
Date: Tue, 5 Aug 2025 17:08:01 +0200
Subject: [PATCH 1/3] nixos/doc/mailman: fix syntax in code block

---
 nixos/modules/services/mail/mailman.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/nixos/modules/services/mail/mailman.md b/nixos/modules/services/mail/mailman.md
index d5a8e5ba84fa..341c3d6744b6 100644
--- a/nixos/modules/services/mail/mailman.md
+++ b/nixos/modules/services/mail/mailman.md
@@ -19,8 +19,8 @@ For a basic configuration with Postfix as the MTA, the following settings are su
       local_recipient_maps = [ "hash:/var/lib/mailman/data/postfix_lmtp" ];
       relay_domains = [ "hash:/var/lib/mailman/data/postfix_domains" ];
       smtpd_tls_chain_files = [
-        config.security.acme.certs."lists.example.org".directory + "/full.pem"
-        config.security.acme.certs."lists.example.org".directory + "/key.pem"
+        (config.security.acme.certs."lists.example.org".directory + "/full.pem")
+        (config.security.acme.certs."lists.example.org".directory + "/key.pem")
       ];
     };
   };

From fed181fac11b376fc242c4805b91d852902fbc35 Mon Sep 17 00:00:00 2001
From: Wolfgang Walther <walther@technowledgy.de>
Date: Tue, 5 Aug 2025 17:08:25 +0200
Subject: [PATCH 2/3] nixos/doc/modular-services: run nixfmt on code blocks

---
 nixos/doc/manual/development/modular-services.md | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/nixos/doc/manual/development/modular-services.md b/nixos/doc/manual/development/modular-services.md
index eadead5c4a40..c34871f7725f 100644
--- a/nixos/doc/manual/development/modular-services.md
+++ b/nixos/doc/manual/development/modular-services.md
@@ -45,11 +45,18 @@ So note that the default value of `system.services.<name>` is not a complete ser
 It is possible to write service modules that are portable. This is done by either avoiding the `systemd` option tree, or by defining process-manager-specific definitions in an optional way:
 
 ```nix
-{ config, options, lib, ... }: {
+{
+  config,
+  options,
+  lib,
+  ...
+}:
+{
   _class = "service";
   config = {
     process.argv = [ (lib.getExe config.foo.program) ];
-  } // lib.optionalAttrs (options?systemd) {
+  }
+  // lib.optionalAttrs (options ? systemd) {
     # ... systemd-specific definitions ...
   };
 }

From a7b3b2584a7b9f204f634714fe9fbe3a3965b06c Mon Sep 17 00:00:00 2001
From: Wolfgang Walther <walther@technowledgy.de>
Date: Tue, 22 Jul 2025 16:12:42 +0200
Subject: [PATCH 3/3] ci/treefmt: add markdown-code-runner

This was run as a test in `doc/tests/check-nix-code-blocks.nix` before,
but its DX can be improved: By including it in `treefmt` we get better
error reporting and auto-fixing, as well as running it on *all* markdown
files (including READMEs etc.) for free.
---
 ci/default.nix                      | 17 +++++++++++++++
 doc/doc-support/package.nix         |  1 -
 doc/tests/check-nix-code-blocks.nix | 32 -----------------------------
 doc/tests/mdcr-config.toml          |  3 ---
 4 files changed, 17 insertions(+), 36 deletions(-)
 delete mode 100644 doc/tests/check-nix-code-blocks.nix
 delete mode 100644 doc/tests/mdcr-config.toml

diff --git a/ci/default.nix b/ci/default.nix
index eaa1879c34b4..727e591a90b8 100644
--- a/ci/default.nix
+++ b/ci/default.nix
@@ -75,6 +75,23 @@ let
           includes = [ "*" ];
           priority = 1;
         };
+
+        # TODO: Upstream this into treefmt-nix eventually:
+        #   https://github.com/numtide/treefmt-nix/issues/387
+        settings.formatter.markdown-code-runner = {
+          command = pkgs.lib.getExe pkgs.markdown-code-runner;
+          options =
+            let
+              config = pkgs.writers.writeTOML "markdown-code-runner-config" {
+                presets.nixfmt = {
+                  language = "nix";
+                  command = [ (pkgs.lib.getExe pkgs.nixfmt) ];
+                };
+              };
+            in
+            [ "--config=${config}" ];
+          includes = [ "*.md" ];
+        };
       };
       fs = pkgs.lib.fileset;
       nixFilesSrc = fs.toSource {
diff --git a/doc/doc-support/package.nix b/doc/doc-support/package.nix
index aefc301ec81c..8ed6865a1c90 100644
--- a/doc/doc-support/package.nix
+++ b/doc/doc-support/package.nix
@@ -137,7 +137,6 @@ stdenvNoCC.mkDerivation (
 
       tests = {
         manpage-urls = callPackage ../tests/manpage-urls.nix { };
-        check-nix-code-blocks = callPackage ../tests/check-nix-code-blocks.nix { };
       };
     };
   }
diff --git a/doc/tests/check-nix-code-blocks.nix b/doc/tests/check-nix-code-blocks.nix
deleted file mode 100644
index 5ec934f6bba8..000000000000
--- a/doc/tests/check-nix-code-blocks.nix
+++ /dev/null
@@ -1,32 +0,0 @@
-{
-  runCommand,
-  markdown-code-runner,
-  nixfmt-rfc-style,
-}:
-
-runCommand "manual_check-nix-code-blocks"
-  {
-    nativeBuildInputs = [
-      markdown-code-runner
-      nixfmt-rfc-style
-    ];
-  }
-  ''
-    set +e
-
-    mdcr --check --config ${./mdcr-config.toml} ${./..}
-
-    if [ $? -ne 0 ]; then
-      cat <<EOF
-    Error: `mdcr` command failed. Please make sure the Nix code snippets in Markdown files are correctly formatted.
-
-    Run this command from the Nixpkgs repository root for automatic formatting:
-
-        mdcr --log debug --config ${toString ./..}/tests/mdcr-config.toml ${toString ./..}
-
-    EOF
-      exit 1
-    fi
-
-    touch "$out"
-  ''
diff --git a/doc/tests/mdcr-config.toml b/doc/tests/mdcr-config.toml
deleted file mode 100644
index 489049f648f0..000000000000
--- a/doc/tests/mdcr-config.toml
+++ /dev/null
@@ -1,3 +0,0 @@
-[presets.nixfmt]
-language = "nix"
-command = ["nixfmt"]