overlay.nix: pass compiler instead of haskell.lib, add couple of fixes

Author: sorki

default.nix

@@ -2,7 +2,7 @@
 , compiler ? null
 }:
 let
-  overlay = import ./overlay.nix pkgs pkgs.haskell.lib;
+  overlay = import ./overlay.nix pkgs compiler;
   overrideHaskellPackages = orig: {
     buildHaskellPackages =
       orig.buildHaskellPackages.override overrideHaskellPackages;

overlay.nix

@@ -1,36 +1,69 @@
-pkgs: hlib: helf: huper:
+pkgs: compiler: hself: hsuper:
 let
   lib = pkgs.lib;
+  haskellLib = pkgs.haskell.lib;
+
+  fetchGitHubPR = { url, sha256 ? throw "sha256 required", ...}@x:
+    let
+      m = builtins.match "https://github.com/(.+)/(.+)/pull/([0-9]+)" url;
+      parts = if m != null then m else throw "Failed to match PR URL";
+    in
+      pkgs.fetchFromGitHub ({
+        owner  = builtins.elemAt parts 0;
+        repo   = builtins.elemAt parts 1;
+        rev    = "refs/pull/${builtins.elemAt parts 2}/head";
+      } // (lib.filterAttrs (n: v: n != "url") x));
 in
 {
   # srk 2023-11-18: this is pinned in nixpkgs unstable to 1.0.5
   # causing trouble with ghc963
-  some = helf.callHackageDirect
+  some = hself.callHackageDirect
     { pkg = "some";
       ver = "1.0.6";
       sha256 = "sha256-AnjaUzSlsLi3lIURrEfs92Jo5FzX49RyNdfDSfFV3Kk=";
     } {};
 
+  # srk 2023-11-19: default in unstable is 0.1.1.1 which
+  # fails to compile test on ghc8107
+  # but for for ghc963 we hit
+  # https://github.com/obsidiansystems/dependent-sum-template/issues/10
+  # so we use 0.1.1.1 for ghc963 and 0.2.0.0 for the rest
+  # - some weird interaction in unstable as this builds
+  # with cabal and 0.2.0.0
+  dependent-sum-template =
+    if compiler == "ghc963"
+    then hsuper.dependent-sum-template
+    else hsuper.dependent-sum-template_0_2_0_0;
+
+  # srk 2023-11-19: wider unix bound via CPP
+  # Required for ghc963 since linux-namespaces is pinned
+  # in unstable to 0.1.3.0
+  linux-namespaces = hself.callCabal2nix "linux-namespaces"
+    (fetchGitHubPR {
+      url = "https://github.com/redneb/hs-linux-namespaces/pull/4";
+      sha256 = "sha256-R61OCu6b4YoDzIl0vg8cSoP7611TlEdWZfVDnZrJY+g=";
+    }) {};
+
   hnix-store-core =
     lib.pipe
-      (helf.callCabal2nix "hnix-store-core" ./hnix-store-core {})
+      (hself.callCabal2nix "hnix-store-core" ./hnix-store-core {})
       [
-        hlib.compose.buildFromSdist
+        haskellLib.compose.buildFromSdist
       ];
   hnix-store-remote =
     lib.pipe
       # enable -fio-testsuite for Linux systems as
       # it requires linux-namespaces
-      # NOTE: we cannot use hlib.compose.enableCabalFlag
+      # NOTE: we cannot use haskellLib.compose.enableCabalFlag
       # as the testsuite deps won't get picked up
       # after cabal2nix step
       (
       if pkgs.stdenv.isDarwin
-      then helf.callCabal2nix "hnix-store-remote" ./hnix-store-remote {}
-      else helf.callCabal2nixWithOptions "hnix-store-remote" ./hnix-store-remote "-fio-testsuite" {}
+      then hself.callCabal2nix "hnix-store-remote" ./hnix-store-remote {}
+      else hself.callCabal2nixWithOptions "hnix-store-remote" ./hnix-store-remote "-fio-testsuite" {}
       )
       [
-        hlib.compose.buildFromSdist
+        haskellLib.compose.buildFromSdist
         (pkg: pkg.overrideAttrs (attrs: {
           buildInputs = attrs.buildInputs ++ [
             pkgs.nix