perf: Remove the quadratic behavior in haskellPackages.ghcWithPackages

lib/deprecated.nix

@@ -157,7 +157,36 @@ rec {
                                 }
                       );
 
-  closePropagation = list: (uniqList {inputList = (innerClosePropagation [] list);});
+  closePropagationSlow = list: (uniqList {inputList = (innerClosePropagation [] list);});
+
+  # This is an optimisation of lib.closePropagation which avoids the O(n^2) behavior
+  # Using a list of derivations, it generates the full closure of the propagatedXXXBuildInputs
+  # The ordering / sorting / comparison is done based on the `outPath`
+  # attribute of each derivation.
+  # On some benchmarks, it performs up to 15 times faster than lib.closePropagation.
+  # See https://github.com/NixOS/nixpkgs/pull/194391 for details.
+  closePropagationFast = list:
+    builtins.map (x: x.val) (builtins.genericClosure {
+      startSet = builtins.map (x: {
+        key = x.outPath;
+        val = x;
+      }) (builtins.filter (x: x != null) list);
+      operator = item:
+        if !builtins.isAttrs item.val then
+          [ ]
+        else
+          builtins.concatMap (x:
+            if x != null then [{
+              key = x.outPath;
+              val = x;
+            }] else
+              [ ]) ((item.val.propagatedBuildInputs or [ ])
+                ++ (item.val.propagatedNativeBuildInputs or [ ]));
+    });
+
+  closePropagation = if builtins ? genericClosure
+    then closePropagationFast
+    else closePropagationSlow;
 
   # calls a function (f attr value ) for each record item. returns a list
   mapAttrsFlatten = f: r: map (attr: f attr r.${attr}) (attrNames r);

nixos/doc/manual/from_md/release-notes/rl-2211.section.xml

@@ -130,6 +130,15 @@
           certificates by default.
         </para>
       </listitem>
+      <listitem>
+        <para>
+          Improved performances of
+          <literal>lib.closePropagation</literal> which was previously
+          quadratic. This is used in e.g.
+          <literal>ghcWithPackages</literal>. Please see backward
+          incompatibilities notes below.
+        </para>
+      </listitem>
       <listitem>
         <para>
           Cinnamon has been updated to 5.4. While at it, the cinnamon
@@ -546,6 +555,12 @@
           notes</link>.
         </para>
       </listitem>
+      <listitem>
+        <para>
+          <literal>lib.closePropagation</literal> now needs that all
+          gathered sets have an <literal>outPath</literal> attribute.
+        </para>
+      </listitem>
       <listitem>
         <para>
           lemmy module option

nixos/doc/manual/release-notes/rl-2211.section.md

@@ -52,6 +52,8 @@ In addition to numerous new and upgraded packages, this release has the followin
 
 - Perl has been updated to 5.36, and its core module `HTTP::Tiny` was patched to verify SSL/TLS certificates by default.
 
+- Improved performances of `lib.closePropagation` which was previously quadratic. This is used in e.g. `ghcWithPackages`. Please see backward incompatibilities notes below.
+
 - Cinnamon has been updated to 5.4. While at it, the cinnamon module now defaults to
   blueman as bluetooth manager and slick-greeter as lightdm greeter to match upstream.
 
@@ -182,6 +184,8 @@ Available as [services.patroni](options.html#opt-services.patroni.enable).
 
 - `teleport` has been upgraded to major version 10. Please see upstream [upgrade instructions](https://goteleport.com/docs/ver/10.0/management/operations/upgrading/) and [release notes](https://goteleport.com/docs/ver/10.0/changelog/#1000).
 
+- `lib.closePropagation` now needs that all gathered sets have an `outPath` attribute.
+
 - lemmy module option `services.lemmy.settings.database.createLocally`
   moved to `services.lemmy.database.createLocally`.
 

pkgs/development/haskell-modules/hoogle.nix

@@ -36,7 +36,6 @@ let
       This index includes documentation for many Haskell modules.
     '';
 
-  # TODO: closePropagation is deprecated; replace
   docPackages = lib.closePropagation
     # we grab the doc outputs
     (map (lib.getOutput "doc") packages);