policy-node/create-item: fix handling of linkables pending activation

Policies need to know if there are session items that are pending
activation. Linkables are not activated in the same order as nodes
appear, which causes problems for e.g. resolving target nodes, if some
of the linkables are pending.

Register linkables in create-items before they are activated.  When
activation completes, remove those that did not activate successfully.
Policies can filter out inactive items by tracking active-features
flags.

If there are existing linkables that are not ready, suspend policy-node
processing, and continue it only after all linkables are ready.

src/scripts/create-item.lua

@@ -58,24 +58,36 @@ end
 
 function addItem (node, item_type)
   local id = node["bound-id"]
+  local item
 
   -- create item
-  items[id] = SessionItem ( item_type )
+  item = SessionItem ( item_type )
+  items[id] = item
 
   -- configure item
-  if not items[id]:configure(configProperties(node)) then
-    Log.warning(items[id], "failed to configure item for node " .. tostring(id))
+  if not item:configure(configProperties(node)) then
+    Log.warning(item, "failed to configure item for node " .. tostring(id))
     return
   end
 
+  item:register ()
+
   -- activate item
   items[id]:activate (Features.ALL, function (item, e)
     if e then
       Log.message(item, "failed to activate item: " .. tostring(e));
+      if item then
+        item:remove ()
+      end
     else
       Log.info(item, "activated item for node " .. tostring(id))
+
+      -- Trigger object managers to update status
+      item:remove ()
+      if item["active-features"] ~= 0 then
         item:register ()
       end
+    end
   end)
 end
 

src/scripts/policy-endpoint-client.lua

@@ -237,6 +237,8 @@ linkables_om = ObjectManager { Interest { type = "SiLinkable",
   -- only handle si-audio-adapter and si-node
   Constraint {
     "item.factory.name", "=", "si-audio-adapter", type = "pw-global" },
+  Constraint {
+    "active-features", "!", 0, type = "gobject" },
   }
 }
 links_om = ObjectManager { Interest { type = "SiLink",

src/scripts/policy-endpoint-device.lua

@@ -199,6 +199,7 @@ linkables_om = ObjectManager {
     -- only handle device si-audio-adapter items
     Constraint { "item.factory.name", "=", "si-audio-adapter", type = "pw-global" },
     Constraint { "item.node.type", "=", "device", type = "pw-global" },
+    Constraint { "active-features", "!", 0, type = "gobject" },
   }
 }
 links_om = ObjectManager {

src/scripts/policy-node.lua

@@ -15,6 +15,8 @@ config.follow = config.follow or false
 local self = {}
 self.scanning = false
 self.pending_rescan = false
+self.events_skipped = false
+self.pending_error_timer = nil
 
 function rescan()
   for si in linkables_om:iterate() do
@@ -526,7 +528,51 @@ end
 
 si_flags = {}
 
+function checkPending ()
+  local pending_linkables = pending_linkables_om:get_n_objects ()
+
+  -- We cannot process linkables if some of them are pending activation,
+  -- because linkables do not appear in the same order as nodes,
+  -- and we cannot resolve target node references until all linkables
+  -- have appeared.
+
+  if self.pending_error_timer then
+    self.pending_error_timer:destroy ()
+    self.pending_error_timer = nil
+  end
+
+  if pending_linkables ~= 0 then
+    -- Wait for linkables to get it sync
+    Log.debug(string.format("pending %d linkable not ready",
+        pending_linkables))
+    self.events_skipped = true
+
+    -- To make bugs in activation easier to debug, emit an error message
+    -- if they occur. policy-node should never be suspended for 20sec.
+    self.pending_error_timer = Core.timeout_add(20000, function()
+        self.pending_error_timer = nil
+        if pending_linkables ~= 0 then
+          Log.message(string.format("%d pending linkable(s) not activated in 20sec. "
+              .. "This should never happen.", pending_linkables))
+        end
+    end)
+
+    return true
+  elseif self.events_skipped then
+    Log.debug("pending linkables ready")
+    self.events_skipped = false
+    scheduleRescan ()
+    return true
+  end
+
+  return false
+end
+
 function handleLinkable (si)
+  if checkPending () then
+    return
+  end
+
   local valid, si_props = checkLinkable(si)
   if not valid then
     return
@@ -697,12 +743,21 @@ clients_om = ObjectManager { Interest { type = "client" } }
 
 devices_om = ObjectManager { Interest { type = "device" } }
 
-
 linkables_om = ObjectManager {
   Interest {
     type = "SiLinkable",
     -- only handle si-audio-adapter and si-node
     Constraint { "item.factory.name", "c", "si-audio-adapter", "si-node" },
+    Constraint { "active-features", "!", 0, type = "gobject" },
+  }
+}
+
+pending_linkables_om = ObjectManager {
+  Interest {
+    type = "SiLinkable",
+    -- only handle si-audio-adapter and si-node
+    Constraint { "item.factory.name", "c", "si-audio-adapter", "si-node" },
+    Constraint { "active-features", "=", 0, type = "gobject" },
   }
 }
 
@@ -786,5 +841,6 @@ metadata_om:activate()
 endpoints_om:activate()
 clients_om:activate()
 linkables_om:activate()
+pending_linkables_om:activate()
 links_om:activate()
 devices_om:activate()