Generate ids for activities.

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -4,9 +4,19 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
   import Ecto.Query
 
   def insert(map) when is_map(map) do
+    map = Map.put_new_lazy(map, "id", &generate_activity_id/0)
+
     Repo.insert(%Activity{data: map})
   end
 
+  def generate_activity_id do
+    host =
+      Application.get_env(:pleroma, Pleroma.Web.Endpoint)
+      |> Keyword.fetch!(:url)
+      |> Keyword.fetch!(:host)
+    "https://#{host}/activities/#{Ecto.UUID.generate}"
+  end
+
   def fetch_public_activities(opts \\ %{}) do
     public = ["https://www.w3.org/ns/activitystreams#Public"]
     fetch_activities(public, opts)

test/web/activity_pub/activity_pub_test.exs

@@ -5,16 +5,26 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubTest do
   alias Pleroma.Builders.ActivityBuilder
 
   describe "insertion" do
-    test "inserts a given map into the activity database" do
+    test "inserts a given map into the activity database, giving it an id if it has none." do
       data = %{
-        ok: true
+        "ok" => true
       }
 
       {:ok, %Activity{} = activity} = ActivityPub.insert(data)
-      assert activity.data == data
+      assert activity.data["ok"] == data["ok"]
-    end
+      assert is_binary(activity.data["id"])
-  end
 
+      given_id = "bla"
+      data = %{
+        "ok" => true,
+        "id" => given_id
+      }
+
+      {:ok, %Activity{} = activity} = ActivityPub.insert(data)
+      assert activity.data["ok"] == data["ok"]
+      assert activity.data["id"] == given_id
+    end
+  end
 
   describe "fetch activities for recipients" do
     test "retrieve the activities for certain recipients" do