api/views/status: prefer 'summary' for attachment alt texts

GtS started exclusively using it and it already worked with Mastodon.
See: https://codeberg.org/superseriousbusiness/gotosocial/issues/4524

Since we used to (implicitly) strip the summary field
this will not take effect retroactively.

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

@@ -15,6 +15,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.AttachmentValidator do
     field(:type, :string)
     field(:mediaType, :string, default: "application/octet-stream")
     field(:name, :string)
+    field(:summary, :string)
     field(:blurhash, :string)
 
     embeds_many :url, UrlObjectValidator, primary_key: false do
@@ -44,7 +45,7 @@ def changeset(struct, data) do
       |> fix_url()
 
     struct
-    |> cast(data, [:id, :type, :mediaType, :name, :blurhash])
+    |> cast(data, [:id, :type, :mediaType, :name, :summary, :blurhash])
     |> cast_embed(:url, with: &url_changeset/2, required: true)
     |> validate_inclusion(:type, ~w[Link Document Audio Image Video])
     |> validate_required([:type, :mediaType])

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -339,6 +339,7 @@ def fix_attachments(%{"attachment" => attachment} = object) when is_list(attachm
           }
           |> Maps.put_if_present("mediaType", media_type)
           |> Maps.put_if_present("name", data["name"])
+          |> Maps.put_if_present("summary", data["summary"])
           |> Maps.put_if_present("blurhash", data["blurhash"])
         else
           nil

lib/pleroma/web/mastodon_api/views/status_view.ex

@@ -610,7 +610,7 @@ def render("attachment.json", %{attachment: attachment}) do
       preview_url: href_preview,
       text_url: href,
       type: type,
-      description: attachment["name"],
+      description: attachment["summary"] || attachment["name"],
       pleroma: %{mime_type: media_type},
       blurhash: attachment["blurhash"]
     }

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

@@ -383,6 +383,32 @@ test "it correctly processes messages with weirdness in address fields" do
       assert ["http://mastodon.example.org/users/admin/followers"] == activity.data["cc"]
       assert ["https://www.w3.org/ns/activitystreams#Public"] == activity.data["to"]
     end
+
+    test "preserves both name and summary of attachments until the end" do
+      name = "marvellous.png"
+      summary = "The most wondrous thing you’ve ever seen."
+
+      data =
+        Jason.decode!(File.read!("test/fixtures/mastodon-post-activity.json"))
+        |> put_in(["object", "attachment"], [
+          %{
+            "type" => "Image",
+            "mediaType" => "image/png",
+            "blurhash" => "LIN1M;~p~W%gt-RPjENI-=RiM_WE",
+            "name" => name,
+            "summary" => summary,
+            "url" => "https://example.org/marvellous.png"
+          }
+        ])
+
+      {:ok, activity} = Transmogrifier.handle_incoming(data)
+      %Object{} = obj = Object.normalize(activity)
+
+      [attach] = obj.data["attachment"]
+
+      assert attach["name"] == name
+      assert attach["summary"] == summary
+    end
   end
 
   describe "`handle_incoming/2`, Mastodon format `replies` handling" do

test/pleroma/web/mastodon_api/views/status_view_test.exs

@@ -667,6 +667,60 @@ test "attachment type will fallback to generic type if inconclusive full media t
     assert resp[:pleroma][:mime_type] == "application/octet-stream"
   end
 
+  test "attachment alt text can use the summary attribute" do
+    # federated like this by e.g. GtS
+    alt_text = "Two sloths hanging from the same branch. It’s sunny."
+
+    attachment_ap = %{
+      "blurhash" => "L38}3{XS9EInNZtSxvxbH=ngocWT",
+      "mediaType" => "image/png",
+      "summary" => alt_text,
+      "type" => "Image",
+      "url" => [
+        %{
+          "type" => "Link",
+          "href" =>
+            "https://gts.exampleorg/fileserver/016VVVVV/attachment/original/01JSXXYZZ.png",
+          "mediaType" => "image/png"
+        }
+      ]
+    }
+
+    resp = StatusView.render("attachment.json", %{attachment: attachment_ap})
+
+    api_spec = Pleroma.Web.ApiSpec.spec()
+    assert_schema(resp, "Attachment", api_spec)
+
+    assert resp[:description] == alt_text
+  end
+
+  test "attachment alt text prefers the summary attribute when name is also present" do
+    alt_text = "Two sloths hanging from the same branch. It’s sunny."
+
+    attachment_ap = %{
+      "blurhash" => "L38}3{XS9EInNZtSxvxbH=ngocWT",
+      "mediaType" => "image/png",
+      "name" => "two_sloths.png",
+      "summary" => alt_text,
+      "type" => "Image",
+      "url" => [
+        %{
+          "type" => "Link",
+          "href" =>
+            "https://gts.exampleorg/fileserver/016VVVVV/attachment/original/01JSXXYZZ.png",
+          "mediaType" => "image/png"
+        }
+      ]
+    }
+
+    resp = StatusView.render("attachment.json", %{attachment: attachment_ap})
+
+    api_spec = Pleroma.Web.ApiSpec.spec()
+    assert_schema(resp, "Attachment", api_spec)
+
+    assert resp[:description] == alt_text
+  end
+
   test "put the url advertised in the Activity in to the url attribute" do
     Pleroma.Config.put([:instance, :limit_to_local_content], false)
     id = "https://wedistribute.org/wp-json/pterotype/v1/object/85810"