test: Install Nix as a CI step (#125)

Author: srid

.github/workflows/ci.yaml

@@ -9,8 +9,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - uses: nixbuild/nix-quick-install-action@v21
+      - uses: nixbuild/nix-quick-install-action@v22
         with:
+          # We use newer Nix for:
+          # - https://github.com/NixOS/nix/issues/7263
+          # - https://github.com/NixOS/nix/issues/7026
+          nix_version: 2.14.1
           nix_conf: |
             experimental-features = nix-command flakes
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}

runtest.sh

@@ -3,6 +3,7 @@
 set -euo pipefail
 
 source ./test/common.sh
+nix --version
 
 # The test directory must contain a 'test.sh' file that will be run in that
 # directory.

test/common.sh

@@ -16,12 +16,18 @@ HASKELL_FLAKE=${DIR_OF_COMMON_SH}/..
 OVERRIDE_HASKELL_FLAKE="--override-input haskell-flake path:${HASKELL_FLAKE}"
 OVERRIDE_NIXPKGS="--override-input nixpkgs github:nixos/nixpkgs/bb31220cca6d044baa6dc2715b07497a2a7c4bc7"
 
-# Waiting on github.com/nixbuild/nix-quick-install-action to support 2.13+
-# We use newer Nix for:
-# - https://github.com/NixOS/nix/issues/7263
-# - https://github.com/NixOS/nix/issues/7026
-nix build --no-link github:nixos/nix/2.14.1
-export PATH=$(nix eval --raw github:nixos/nix/2.14.1#default.outPath)/bin:$PATH
-echo $PATH
-nix --version
+currentver="$(nix eval --raw --expr builtins.nixVersion)"
+requiredver="2.14.1"
+if [ "$(printf '%s\n' "$requiredver" "$currentver" | sort -V | head -n1)" = "$requiredver" ];
+then 
+  echo
+else
+  echo "!!!! Your Nix version is old ($currentver). Using newer Nix from github:nixos/nix/2.14.1"
+  # We use newer Nix for:
+  # - https://github.com/NixOS/nix/issues/7263
+  # - https://github.com/NixOS/nix/issues/7026
+  nix build --no-link github:nixos/nix/2.14.1
+  export PATH=$(nix eval --raw github:nixos/nix/2.14.1#default.outPath)/bin:$PATH
+fi
 
+nix --version