From 58cdd4e315e3eec80ea70b2772bcd3694b0ca64f Mon Sep 17 00:00:00 2001
From: Pol Dellaiera <pol.dellaiera@protonmail.com>
Date: Fri, 11 Apr 2025 09:31:45 +0200
Subject: [PATCH] {nixpkgs-manual, nixos-manual}: add new test
 `check-nix-code-blocks`

---
 doc/doc-support/package.nix         |  7 ++++++-
 doc/tests/check-nix-code-blocks.nix | 32 +++++++++++++++++++++++++++++
 doc/tests/mdcr-config.toml          |  3 +++
 3 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 doc/tests/check-nix-code-blocks.nix
 create mode 100644 doc/tests/mdcr-config.toml

diff --git a/doc/doc-support/package.nix b/doc/doc-support/package.nix
index f316656a585c..dfe7a3c4cc9b 100644
--- a/doc/doc-support/package.nix
+++ b/doc/doc-support/package.nix
@@ -12,6 +12,7 @@
   nixos-render-docs-redirects,
   writeShellScriptBin,
   nixpkgs ? { },
+  markdown-code-runner,
 }:
 
 stdenvNoCC.mkDerivation (
@@ -119,10 +120,14 @@ stdenvNoCC.mkDerivation (
           packages = [
             devmode'
             nixos-render-docs-redirects'
+            markdown-code-runner
           ];
         };
 
-      tests.manpage-urls = callPackage ../tests/manpage-urls.nix { };
+      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
new file mode 100644
index 000000000000..5ec934f6bba8
--- /dev/null
+++ b/doc/tests/check-nix-code-blocks.nix
@@ -0,0 +1,32 @@
+{
+  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
new file mode 100644
index 000000000000..489049f648f0
--- /dev/null
+++ b/doc/tests/mdcr-config.toml
@@ -0,0 +1,3 @@
+[presets.nixfmt]
+language = "nix"
+command = ["nixfmt"]