Upgrade Nix script to use the haskell-updates branch.

The haskell-updates branch is already on Stackage nightly, which allows for a
much better cache hit rate (assuming haskell-updates is backed by a Hydra cache,
which I'm not quite sure of).

Author: pepeiborra

nix/default.nix

@@ -0,0 +1,39 @@
+{ sources ? import ./sources.nix }:
+let
+  overlay = _self: pkgs:
+    let sharedOverrides = {
+        overrides = _self: super: {
+            mkDerivation = args: super.mkDerivation (args //
+                {
+                    # skip running tests for Hackage packages
+                    doCheck =
+                        # but not for ghcide
+                        args.version == "0";
+                    # relax upper bounds
+                    jailbreak = args.pname != "jailbreak-cabal";
+                });
+            };
+            };
+        extended = haskellPackages:
+          haskellPackages.extend (pkgs.haskell.lib.packageSourceOverrides {
+            haskell-language-server = ../.;
+            ghcide = ../ghcide;
+            hie-compat = ../ghcide/hie-compat;
+            hls-plugin-api = ../hls-plugin-api;
+            hls-tactics-plugin = ../plugins/tactics;
+            hls-hlint-plugin = ../plugins/hls-hlint-plugin;
+          });
+        in
+        {
+        inherit (import sources.gitignore { inherit (pkgs) lib; }) gitignoreSource;
+        ourHaskell = pkgs.haskell // {
+            packages = pkgs.haskell.packages // {
+                # relax upper bounds on ghc 8.10.x versions (and skip running tests)
+                ghc8101 = extended (pkgs.haskell.packages.ghc8101.override sharedOverrides);
+                ghc8102 = extended (pkgs.haskell.packages.ghc8102.override sharedOverrides);
+            };
+        };
+        };
+
+in import sources.nixpkgs
+{ overlays = [ overlay ] ; config = {allowBroken = true;}; }

nix/sources.json

@@ -1,4 +1,16 @@
 {
+    "gitignore": {
+        "branch": "master",
+        "description": "Nix function for filtering local git sources",
+        "homepage": "",
+        "owner": "hercules-ci",
+        "repo": "gitignore",
+        "rev": "c4662e662462e7bf3c2a968483478a665d00e717",
+        "sha256": "1npnx0h6bd0d7ql93ka7azhj40zgjp815fw2r6smg8ch9p7mzdlx",
+        "type": "tarball",
+        "url": "https://github.com/hercules-ci/gitignore/archive/c4662e662462e7bf3c2a968483478a665d00e717.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
     "niv": {
         "branch": "master",
         "description": "Easy dependency management for Nix projects",
@@ -12,15 +24,15 @@
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs": {
-        "branch": "nixpkgs-unstable",
+        "branch": "haskell-updates",
         "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
         "homepage": "https://github.com/NixOS/nixpkgs",
         "owner": "NixOS",
-        "repo": "nixpkgs-channels",
-        "rev": "a332da8588aeea4feb9359d23f58d95520899e3c",
-        "sha256": "18hlja5syv3xpi14c07h9lrn1cchq2azmj06fyalq52vl064nx75",
+        "repo": "nixpkgs",
+        "rev": "cbf707b2af4cd66bdcdd84b2bddfb627194b39c0",
+        "sha256": "1bj55jkgdzx7lv6dvy26l354c7vsxaa1jipm99axgqqax905m8sa",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs-channels/archive/a332da8588aeea4feb9359d23f58d95520899e3c.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/cbf707b2af4cd66bdcdd84b2bddfb627194b39c0.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     }
 }

shell.nix

@@ -1,125 +1,46 @@
 # This shell.nix file is designed for use with cabal build
-# It aims to leverage the nix cache in as much as possible
-# while reducing Nix maintenance costs.
-# It does **not** aim to replace Cabal/Stack with Nix
+# It does **not** aim to replace Cabal
 
 # Maintaining this file:
 #
-# - Dealing with broken nix-shell
-#
-#     1. Bump the nixpkgs version using `niv update nixpkgs`
-#     2. Comment out any remaining failing packages
-#
-# - Dealing with broken cabal build inside nix-shell:
-#
-#    If my understanding of cabal new-build is correct this should never happen,
-#    assuming that cabal new-build does succeed outside nix-shell
+#     - Bump the nixpkgs version using `niv update nixpkgs`
 
-{ sources ? import nix/sources.nix,
-  nixpkgs ? import sources.nixpkgs { },
-  compiler ? "default",
-  hoogle ? false
+{ compiler ? "default",
+  withHoogle ? false,
+  nixpkgs ? import ./nix {}
  }:
+
 with nixpkgs;
 
 let defaultCompiler = "ghc" + lib.replaceStrings ["."] [""] haskellPackages.ghc.version;
-    haskellPackagesForProject = p:
-        if compiler == "default" || compiler == defaultCompiler
-            then if hoogle
-                then haskellPackages.ghcWithHoogle p
-                else haskellPackages.ghcWithPackages p
-            # for all other compilers there is no Nix cache so dont bother building deps
-            else if hoogle
-                then  haskell.packages.${compiler}.ghcWithHoogle (_: [])
-                else haskell.packages.${compiler}.ghcWithPackages (_: []);
+    haskellPackagesForProject =
+        if compiler == "default"
+            then ourHaskell.packages.${defaultCompiler}
+            else ourHaskell.packages.${compiler};
+
+    packages = p: [ p.haskell-language-server
+                    p.ghcide
+                    p.hie-compat
+                    p.hls-plugin-api
+                    p.hls-tactics-plugin
+                    p.hls-hlint-plugin
+                  ];
 
-    retrie = with haskell.lib; dontCheck(disableLibraryProfiling(haskellPackages.retrie));
-    compilerWithPackages = haskellPackagesForProject(p:
-        with p;
-        [
-          Diff
-          Glob
-          HsYAML-aeson
-          QuickCheck
-          aeson
-          alex
-          async
-          base16-bytestring
-          blaze-builder
-          blaze-markup
-          brittany
-          conduit-extra
-          conduit-parse
-          cryptohash-sha1
-          data-default
-          data-default-class
-          data-default-instances-containers
-          data-default-instances-dlist
-          data-default-instances-old-locale
-          extra
-          floskell
-        #   fourmolu
-          fuzzy
-          generic-deriving
-          ghc-check
-          gitrev
-          haddock-library
-          happy
-          haskell-lsp
-          haskell-src-exts
-          hie-bios
-          hslogger
-          hspec
-          lens
-          lsp-test
-          megaparsec
-          network
-          opentelemetry
-          optparse-simple
-          ormolu
-          parser-combinators
-          parsers
-          prettyprinter
-          prettyprinter-ansi-terminal
-          primes
-          psqueues
-          regex-tdfa
-          retrie
-          rope-utf16-splay
-          safe-exceptions
-          shake
-          sorted-list
-          strict
-          stylish-haskell
-          tasty
-          tasty-ant-xml
-          tasty-expected-failure
-          tasty-golden
-          tasty-hunit
-          tasty-rerun
-          temporary
-          text
-          typed-process
-          unix-compat
-          unordered-containers
-          xml
-          yaml
-          zlib
-         ]);
+    isSupported = compiler == "default" || compiler == defaultCompiler;
 in
-stdenv.mkDerivation {
-  name = "haskell-language-server";
+haskellPackagesForProject.shellFor {
+  inherit withHoogle;
+  doBenchmark = true;
+  packages = p: if isSupported then packages p else [p.ghc-paths];
   buildInputs = [
-    git
     gmp
-    ncurses
     zlib
+    ncurses
 
     haskellPackages.cabal-install
     haskellPackages.hlint
-
-    compilerWithPackages
-
+    haskellPackages.ormolu
+    haskellPackages.stylish-haskell
   ];
   src = null;
   shellHook = ''