test: add docSupport test and add docSupport version check

flake.nix

@@ -26,7 +26,7 @@
           versionedPackageFnWithOverrides = { version, versionSource }:
             let pkg =
               pkgs.callPackage packageFn {
-                inherit version versionSource;
+                inherit version versionSource versionComparison;
               };
             in
             applyOverrides {
@@ -191,6 +191,24 @@
                   ruby -e 'require "foobar"; say' > $out
                 '';
               };
+            }) // (lib.optionalAttrs (with versionComparison rubyVersion; greaterOrEqualTo "3.4") {
+              "${rubyName}-docSupport" = {
+                nativeBuildInputs = [
+                  (ruby.override { docSupport = true; })
+                ];
+                command = ''
+                  HOME=$TMPDIR ri Array > $out
+                '';
+              };
+            }) // (lib.optionalAttrs (with versionComparison rubyVersion; lessThan "3.4") {
+              "${rubyName}-docSupport-noParallel" = {
+                nativeBuildInputs = [
+                  (ruby.override { docSupport = true; parallelBuild = false; })
+                ];
+                command = ''
+                  HOME=$TMPDIR ri Array > $out
+                '';
+              };
             })
           ) rubyPackages;
 

ruby/package-fn.nix

@@ -1,5 +1,6 @@
 { version
 , versionSource
+, versionComparison
 , libDir ? "${(import ./parse-version.nix version).majMin}.0"
 , rubygems ? null
 , stdenv
@@ -25,6 +26,7 @@
 , bundler
 , bundix
 , removeReferencesTo
+, parallelBuild ? true
 , useRailsExpress ? true
 , zlibSupport ? true
 , opensslSupport ? true
@@ -87,7 +89,7 @@ let
       propagatedBuildInputs =
         (op jemallocSupport jemalloc);
 
-      enableParallelBuilding = true;
+      enableParallelBuilding = parallelBuild;
 
       postPatch = ''
         ${opString (rubygems != null) ''
@@ -107,6 +109,11 @@ let
 
       preConfigure = ''
         sed -i configure -e 's/;; #(/\n;;/g'
+        ${opString docSupport ''
+          # rdoc creates XDG_DATA_DIR (defaulting to $HOME/.local/share) even if
+          # it's not going to be used.
+          export HOME=$TMPDIR
+        ''}
       '';
 
       configureFlags =
@@ -195,4 +202,7 @@ let
       };
     };
 in
+# There's a known race condition when building with docs enabled before Ruby 3.4.0
+# Building documents requires parallelBuild to be false in those versions
+assert docSupport -> (with versionComparison version; greaterOrEqualTo "3.4.0" || !parallelBuild);
 self

rubygems/package-fn.nix

@@ -3,6 +3,7 @@
 , stdenv
 , fetchurl
 , fetchpatch
+, ...
 }:
 stdenv.mkDerivation {
   pname = "rubygems";