Merge pull request #2984 from jaschutte/flake-pin-minor-versions

Pin Nix GHC minor version

Author: jaschutte

README.md

@@ -116,7 +116,7 @@ Or [use Nix](https://nixos.org/nix/download.html) to get a shell with the `clash
 nix develop .
 
 # Start a dev shell with a specific GHC version
-nix develop .#ghc961
+nix develop .#ghc9101
 ```
 
 You will need a modern version of nix with support for the new-style `nix`

flake.nix

@@ -36,12 +36,12 @@
       # The versions of GHC that we want to be able to build / develop against
       # within the nix environment. Since nix is lazy, only derivations for
       # versions of GHC which are used are actually evaluated.
-      ghcVersions = [ "ghc96" "ghc98" "ghc910" ];
+      ghcVersions = [ "ghc964" "ghc982" "ghc9101" ];
 
       # We pick a single version of GHC to use by default within nix. This is
       # probably cleaner than always having N copies of each package / app and
       # being forced to refer to them by their GHC version.
-      defaultGhcVersion = "ghc910";
+      defaultGhcVersion = "ghc9101";
 
       # Overlays are not per-system, so let's only compute them once.
       # For each version of GHC we produce a `pkgs.clashPackages-ghcVER`, e.g.

nix/overlay.nix

@@ -15,7 +15,9 @@ compilerVersion:
 final: prev:
 let
   # An overlay with the things we need to change for the specified GHC version.
-  ghcOverlay = import (./. + "/overlay-${compilerVersion}.nix") {
+  # The overlays are named without the GHC minor version, so we need to strip the last character from the version
+  strippedMinorVersion = builtins.substring 0 (builtins.stringLength compilerVersion - 1) compilerVersion;
+  ghcOverlay = import (./. + "/overlay-${strippedMinorVersion}.nix") {
     pkgs = prev;
   };