scripts: populate session.services via a script

See pipewire!1409 / wireplumber!441

src/config/wireplumber.conf

@@ -129,6 +129,7 @@ wireplumber.profiles = {
     check.no-media-session = required
     support.settings = required
     support.log-settings = required
+    support.session-services = required
   }
 
   # Disable features that are meant only for user sessions
@@ -339,6 +340,12 @@ wireplumber.components = [
     provides = metadata.sm-objects
   }
 
+  ## Populates the "session.services" property on the WirePlumber client object
+  {
+    name = session-services.lua, type = script/lua
+    provides = support.session-services
+  }
+
   ## Device monitors' optional features
   {
     type = virtual, provides = monitor.alsa.reserve-device,
@@ -738,6 +745,17 @@ wireplumber.components.rules = [
       }
     }
   }
+  # session-services.lua must execute at the very end
+  {
+    matches = [
+      { name = "!session-services.lua" }
+    ]
+    actions = {
+      merge = {
+        before = [ support.session-services ]
+      }
+    }
+  }
 ]
 
 wireplumber.settings.schema = {

src/scripts/session-services.lua

@@ -0,0 +1,38 @@
+-- WirePlumber
+--
+-- Copyright © 2024 Collabora Ltd.
+--
+-- SPDX-License-Identifier: MIT
+
+local features_to_services = {
+  ["monitor.alsa"] = { "audio", "api.alsa" },
+  ["monitor.alsa-midi"] = { "midi", "api.alsa-seq" },
+  ["monitor.bluez"] = { "bluetooth.audio", "api.bluez" },
+  ["monitor.bluez-midi"] = { "bluetooth.midi", "api.bluez" },
+  ["monitor.v4l2"] = { "video-capture", "api.v4l2" },
+  ["monitor.libcamera"] = { "video-capture", "api.libcamera" },
+  ["policy.device.profile"] = { "policy.device.profile" },
+  ["policy.device.routes"] = { "policy.device.routes" },
+  ["policy.default-nodes"] = { "policy.default-nodes" },
+  ["policy.linking.standard"] = { "policy.linking.standard" },
+  ["policy.linking.role-based"] = { "policy.linking.role-based" },
+}
+
+local services = {}
+for k, v in pairs (features_to_services) do
+  if Core.test_feature (k) then
+    for _, s in pairs (v) do
+      services[s] = s
+    end
+  end
+end
+
+-- convert to array with numeric indices
+local services_array = {}
+for _, s in pairs (services) do
+  table.insert (services_array, s)
+end
+
+Core.update_properties {
+  ["session.services"] = "[" .. table.concat (services_array, ", ") .. "]"
+}