haskellPackages.haskell-language-server: Try to fix tests

pkgs/development/haskell-modules/configuration-common.nix

@@ -1410,7 +1410,13 @@ self: super: {
   # overriding aeson on all of them to prevent double compilations
   # this shouldn‘t break anything because nearly all their reverse deps are
   # in this list or marked as broken anyways
-  haskell-language-server = dontCheck super.haskell-language-server;
+  # 2020-11-19: Checks nearly fixed, but still disabled because of flaky tests:
+  # https://github.com/haskell/haskell-language-server/issues/610
+  # https://github.com/haskell/haskell-language-server/issues/611
+  haskell-language-server = dontCheck (super.haskell-language-server.override {
+    lsp-test = dontCheck self.lsp-test_0_11_0_7;
+  });
+
   fourmolu = dontCheck super.fourmolu;
   ghcide = dontCheck (appendPatch super.ghcide (pkgs.fetchpatch {
     # 2020-11-13: Bumping bounds via an already upstream merged change

pkgs/development/haskell-modules/configuration-nix.nix

@@ -823,5 +823,11 @@ self: super: builtins.intersectAttrs super {
         ln -s $out/bin/haskell-language-server $out/bin/haskell-language-server-${ghc_version}
         ln -s $out/bin/haskell-language-server $out/bin/haskell-language-server-${ghc_major_version}
        '';
+    testToolDepends = [ self.cabal-install pkgs.git ];
+    testTarget = "func-test"; # wrapper test accesses internet
+    preCheck = ''
+      export PATH=$PATH:$PWD/dist/build/haskell-language-server:$PWD/dist/build/haskell-language-server-wrapper
+      export HOME=$TMPDIR
+    '';
   });
 }