chore(packages): Protect existing instances of packages

This re-runs the _init() function to potentially force a reload or
change options, but it avoids re-instantiating a new instance from the
package class.

classes/base.lua

@@ -183,14 +183,31 @@ end
 
 function class:loadPackage (packname, options, reload)
   local pack
+  -- Allow loading by injecting whole packages as-is, otherwise try to load it with the usual packages path.
   if type(packname) == "table" then
-     pack = packname
+    pack, packname = packname, packname._name
   else
-     pack = require(("packages.%s"):format(packname))
+    pack = require(("packages.%s"):format(packname))
+    if pack._name ~= packname then
+      SU.error(("Loaded module name '%s' does not match requested name '%s'"):format(pack._name, packname))
+    end
   end
-  if type(pack) == "table" and pack.type == "package" then -- new package
-    local name = pack._name
-    self.packages[name] = pack(options, reload)
+  SILE.packages[packname] = pack
+  if type(pack) == "table" and pack.type == "package" then -- current package api
+    if self.packages[packname] then
+      -- If the same package name has been loaded before, we might be loading a modified version of the same package or
+      -- we might be re-loading the same package, or we might just be doubling up work because somebody called us twice.
+      -- The package itself should take care of the difference between load and reload based on the reload flag here,
+      -- but in addition to that we also want to avoid creating a new instance. We want to run the intitializer from the
+      -- (possibly different) new module, but not create a new instance ID and loose any connections it made.
+      -- To do this we add a create function that returns the current instance. This brings along the _initialized flag
+      -- and of course anything else already setup and running.
+      local current_instance = self.packages[packname]
+      pack._create = function () return current_instance end
+      pack(options, true)
+    else
+      self.packages[packname] = pack(options, reload)
+    end
   else -- legacy package
     self:initPackage(pack, options)
   end

core/sile.lua

@@ -211,6 +211,7 @@ SILE.use = function (module, options, reload)
     SILE.pagebuilders[name] = pack
     SILE.pagebuilder = pack(options)
   elseif pack.type == "package" then
+    SILE.packages[pack._name] = pack
     if class then
        class:loadPackage(pack, options, reload)
     else