build: setup nix flake and use it for gh actions

.envrc

@@ -0,0 +1,5 @@
+# shellcheck shell=bash
+if ! has nix_direnv_version || ! nix_direnv_version 3.0.6; then
+  source_url "https://raw.githubusercontent.com/nix-community/nix-direnv/3.0.6/direnvrc" "sha256-RYcUJaRMf8oF5LznDrlCXbkOQrywm0HDv1VjYGaJGdM="
+fi
+use flake

.github/workflows/ci.yml

@@ -11,29 +11,13 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: teatimeguest/setup-texlive-action@v3
+      - uses: cachix/install-nix-action@v27
         with:
-          packages: >-
-            scheme-basic
-            beamer
-            biblatex
-            enumitem
-            fileinfo
-            hypdoc
-            hyperref
-            l3build
-            listings
-            metalogo
-            parskip
-            pgf
-            pgfopts
-            setspace
-            xurl
-            microtype
+          github_access_token: ${{ secrets.GITHUB_TOKEN }}
       - name: document
-        run: l3build doc
+        run: nix develop --command l3build doc
       - name: build
-        run: l3build ctan -q -H --show-log-on-error
+        run: nix develop --command l3build ctan -q -H --show-log-on-error
   release:
     if: ${{ github.ref == 'refs/heads/main' }}
     permissions:

.gitignore

@@ -310,3 +310,12 @@ build/
 .oc
 *.curlopt
 *.zip
+
+# nix -----------------------------------------------
+
+# Ignore build outputs from performing a nix-build or `nix build` command
+result
+result-*
+
+# Ignore direnv folder
+.direnv/

flake.nix

@@ -0,0 +1,77 @@
+{
+  description = "A basic flake with a shell";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  inputs.systems.url = "github:nix-systems/default";
+  inputs.flake-utils = {
+    url = "github:numtide/flake-utils";
+    inputs.systems.follows = "systems";
+  };
+
+  outputs =
+    { nixpkgs, flake-utils, ... }:
+    flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+        texlive = pkgs.texlive.combine {
+          inherit (pkgs.texlive)
+            scheme-basic
+            l3build
+            beamer
+            biblatex
+            enumitem
+            fileinfo
+            hypdoc
+            hyperref
+            listings
+            metalogo
+            parskip
+            pgf
+            pgfopts
+            setspace
+            xurl
+            microtype
+            ;
+        };
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          buildInputs = [
+            texlive
+          ];
+          shellHook = ''
+            export TEXMF="${texlive}/"
+          '';
+        };
+      }
+    );
+}
+# {
+#   inputs = {
+#     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+#     flake-utils.url = "github:numtide/flake-utils";
+#   };
+#
+#   outputs = {
+#     self,
+#     nixpkgs,
+#     flake-utils,
+#   }:
+#     flake-utils.lib.eachDefaultSystem (
+#       system: let
+#         pkgs = nixpkgs.legacyPackages.${system};
+#         texlive = pkgs.texlive.combine {inherit (pkgs.texlive) scheme-basic l3build;};
+#         l3build-wrapped = pkgs.writeShellScriptBin "l3build-wrapped" ''
+#           # NOTE: the trailing slash in TEXMF is required
+#           TEXMF="${texlive}/" ${texlive}/bin/l3build "$@"
+#         '';
+#       in {
+#         devShells.default = pkgs.mkShell {
+#           buildInputs = [
+#             texlive
+#             l3build-wrapped
+#           ];
+#         };
+#       }
+#     );
+# }