Resolve gap-system/gap#5761

Author: james-d-mitchell

PackageInfo.g

@@ -399,13 +399,24 @@ Dependencies := rec(
 
 AvailabilityTest := function()
   local digraphs_so;
-  digraphs_so := Filename(DirectoriesPackagePrograms("digraphs"),
-                          "digraphs.so");
-  if (not "digraphs" in SHOW_STAT()) and digraphs_so = fail then
-     LogPackageLoadingMessage(PACKAGE_WARNING,
+
+  if CompareVersionNumbers(GAPInfo.Version, "4.12") then
+    if not IsKernelExtensionAvailable("digraphs") then
+      LogPackageLoadingMessage(PACKAGE_WARNING,
                               ["the kernel module is not compiled, ",
                                "the package cannot be loaded."]);
-    return fail;
+      return fail;
+    fi;
+  else
+    # TODO this clause can be removed once Digraphs requires GAP>=4.12.1
+    digraphs_so := Filename(DirectoriesPackagePrograms("digraphs"),
+                            "digraphs.so");
+    if (not "digraphs" in SHOW_STAT()) and digraphs_so = fail then
+       LogPackageLoadingMessage(PACKAGE_WARNING,
+                                ["the kernel module is not compiled, ",
+                                 "the package cannot be loaded."]);
+      return fail;
+    fi;
   fi;
   return true;
 end,

init.g

@@ -13,15 +13,23 @@ if not IsBound(UserHomeExpand) then
   BindGlobal("UserHomeExpand", USER_HOME_EXPAND);
 fi;
 
-# load kernel function if it is installed:
-if not IsBound(DIGRAPH_OUT_NBS) and "digraphs" in SHOW_STAT() then
-  # try static module
-  LoadStaticModule("digraphs");
-fi;
-if not IsBound(DIGRAPH_OUT_NBS) and
-    Filename(DirectoriesPackagePrograms("digraphs"), "digraphs.so") <> fail then
-  LoadDynamicModule(Filename(DirectoriesPackagePrograms("digraphs"),
-                             "digraphs.so"));
+if CompareVersionNumbers(GAPInfo.Version, "4.12") then
+  if not LoadKernelExtension("digraphs") then
+    Error("failed to load the Digraphs package kernel extension");
+  fi;
+else
+  # TODO this clause can be removed once Digraphs requires GAP>=4.12.1
+  # load kernel function if it is installed:
+  if not IsBound(DIGRAPH_OUT_NBS) and "digraphs" in SHOW_STAT() then
+    # try static module
+    LoadStaticModule("digraphs");
+  fi;
+  if not IsBound(DIGRAPH_OUT_NBS) and
+      Filename(DirectoriesPackagePrograms("digraphs"),
+               "digraphs.so") <> fail then
+    LoadDynamicModule(Filename(DirectoriesPackagePrograms("digraphs"),
+                               "digraphs.so"));
+  fi;
 fi;
 
 BindGlobal("DIGRAPHS_IsGrapeLoaded",