AP ingest: infer tag type when missing

lib/pleroma/web/activity_pub/object_validators/tag_validator.ex

@@ -80,6 +80,27 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.TagValidator do
     |> Map.put(:action, :ignore)
   end
 
+  def changeset(struct, data) when is_map(data) do
+    data = infer_type(data)
+
+    if Map.has_key?(data, "type") do
+      changeset(struct, data)
+    else
+      struct
+      |> cast(data, [])
+      |> Map.put(:action, :ignore)
+    end
+  end
+
+  defp infer_type(%{"type" => _} = data), do: data
+  defp infer_type(%{"name" => "#" <> _} = data), do: Map.put(data, "type", "Hashtag")
+  defp infer_type(%{"name" => "@" <> _} = data), do: Map.put(data, "type", "Mention")
+
+  defp infer_type(%{"mediaType" => _media_type, "href" => _href} = data),
+    do: Map.put(data, "type", "Link")
+
+  defp infer_type(data), do: data
+
   def icon_changeset(struct, data) do
     struct
     |> cast(data, [:type, :url])

test/fixtures/fedidev.fun/tag_hashtag_missing_type.json

@@ -0,0 +1,30 @@
+{
+  "@context": [
+    "https://www.w3.org/ns/activitystreams"
+  ],
+  "type": "Create",
+  "id": "https://fedidev.fun/activity/tag-hashtag-missing-type",
+  "actor": "https://fedidev.fun/users/alice",
+  "to": [
+    "https://www.w3.org/ns/activitystreams#Public"
+  ],
+  "cc": [],
+  "published": "2025-11-21T14:41:00Z",
+  "object": {
+    "type": "Note",
+    "id": "https://fedidev.fun/objects/note-tag-hashtag-missing-type",
+    "attributedTo": "https://fedidev.fun/users/alice",
+    "to": [
+      "https://www.w3.org/ns/activitystreams#Public"
+    ],
+    "cc": [],
+    "published": "2025-11-21T14:41:00Z",
+    "content": "hashtag without type",
+    "tag": [
+      {
+        "name": "#Test"
+      }
+    ]
+  }
+}
+

test/fixtures/fedidev.fun/tag_mention_missing_type.json

@@ -0,0 +1,31 @@
+{
+  "@context": [
+    "https://www.w3.org/ns/activitystreams"
+  ],
+  "type": "Create",
+  "id": "https://fedidev.fun/activity/tag-mention-missing-type",
+  "actor": "https://fedidev.fun/users/alice",
+  "to": [
+    "https://www.w3.org/ns/activitystreams#Public"
+  ],
+  "cc": [],
+  "published": "2025-11-21T14:41:01Z",
+  "object": {
+    "type": "Note",
+    "id": "https://fedidev.fun/objects/note-tag-mention-missing-type",
+    "attributedTo": "https://fedidev.fun/users/alice",
+    "to": [
+      "https://www.w3.org/ns/activitystreams#Public"
+    ],
+    "cc": [],
+    "published": "2025-11-21T14:41:01Z",
+    "content": "mention without type",
+    "tag": [
+      {
+        "name": "@bob",
+        "href": "https://remote.example/users/bob"
+      }
+    ]
+  }
+}
+

test/pleroma/web/activity_pub/transmogrifier/fedidev_fun_tag_inference_test.exs

@@ -0,0 +1,65 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.Transmogrifier.FedidevFunTagInferenceTest do
+  use Oban.Testing, repo: Pleroma.Repo
+  use Pleroma.DataCase
+
+  alias Pleroma.Object
+  alias Pleroma.User
+  alias Pleroma.Web.ActivityPub.Transmogrifier
+
+  import Pleroma.Factory
+
+  setup_all do
+    Tesla.Mock.mock_global(fn env -> apply(HttpRequestMock, :request, [env]) end)
+    :ok
+  end
+
+  defp ensure_remote_actor!(ap_id) when is_binary(ap_id) do
+    case User.get_cached_by_ap_id(ap_id) do
+      %User{} ->
+        :ok
+
+      _ ->
+        insert(:user,
+          local: false,
+          ap_id: ap_id,
+          follower_address: ap_id <> "/followers",
+          following_address: ap_id <> "/following",
+          featured_address: ap_id <> "/collections/featured",
+          inbox: ap_id <> "/inbox"
+        )
+
+        :ok
+    end
+  end
+
+  defp ingest_fixture!(rel_path) do
+    data = rel_path |> File.read!() |> Jason.decode!()
+    ensure_remote_actor!(data["actor"])
+
+    assert {:ok, activity} = Transmogrifier.handle_incoming(data)
+    object = Object.normalize(activity.data["object"], fetch: false)
+
+    {activity, object}
+  end
+
+  test "infers Hashtag type when missing" do
+    {_activity, object} =
+      ingest_fixture!("test/fixtures/fedidev.fun/tag_hashtag_missing_type.json")
+
+    assert "test" in Object.hashtags(object)
+  end
+
+  test "infers Mention type when missing" do
+    {_activity, object} =
+      ingest_fixture!("test/fixtures/fedidev.fun/tag_mention_missing_type.json")
+
+    assert Enum.any?(object.data["tag"], fn
+             %{"type" => "Mention", "href" => "https://remote.example/users/bob"} -> true
+             _ -> false
+           end)
+  end
+end