From 2e7c521d70ac562ec0e5dae4df0f1538bcb5ef54 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakub=20Kopa=C5=84ski?= <jakub@famisoft.pl>
Date: Tue, 6 Feb 2024 16:21:41 +0100
Subject: [PATCH] Check for leftover white space

Agda stdlib team recommends to run
[fix-whitespace](https://github.com/agda/agda-stdlib/blob/master/HACKING.md#how-to-enforce-whitespace-policies)
in order to get rid of unnecessary white space characters.  I've added
this tool to the nix dev shell, as well as formed a check that will be
can be run with `nix flake check` command.  As of now this is entirely
opt-in as this check is not enabled in (and thus won't fail) the CI.
---
 fix-whitespace.yaml | 13 +++++++++++++
 flake.nix           | 14 +++++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 fix-whitespace.yaml

diff --git a/fix-whitespace.yaml b/fix-whitespace.yaml
new file mode 100644
index 0000000..2ca3b5a
--- /dev/null
+++ b/fix-whitespace.yaml
@@ -0,0 +1,13 @@
+included-dirs:
+  - src
+
+included-files:
+  - "*.agda"
+  - "*.md"
+  - "*.org"
+  - "*.nix"
+
+excluded-dirs:
+  - .git
+  - .direnv
+  - result
diff --git a/flake.nix b/flake.nix
index ff3b77e..67268aa 100644
--- a/flake.nix
+++ b/flake.nix
@@ -21,10 +21,22 @@
         agdaWithStandardLibrary = pkgs.agda.withPackages (_: [ standard-library ]);
 
       in {
-        devShell = pkgs.mkShell {
+        checks.whitespace = pkgs.stdenvNoCC.mkDerivation {
+          name = "check-whitespace";
+          dontBuild = true;
+          src = ./.;
+          doCheck = true;
+          checkPhase = ''
+            ${pkgs.haskellPackages.fix-whitespace}/bin/fix-whitespace --check
+          '';
+          installPhase = ''mkdir "$out"'';
+        };
+
+        devShells.default = pkgs.mkShell {
           buildInputs = [
             agdaWithStandardLibrary
             pkgs.graphviz
+            pkgs.haskellPackages.fix-whitespace
           ];
         };