From 39dc6c65ef7a95412a985a3edce019914af12df8 Mon Sep 17 00:00:00 2001
From: "Haelwenn (lanodan) Monnier" <contact@hacktivis.me>
Date: Fri, 29 Dec 2023 05:23:01 +0100
Subject: [PATCH] ChatMessage: Tolerate attachment field set to an empty array

Closes: https://git.pleroma.social/pleroma/pleroma/-/issues/3224
---
 changelog.d/chat-attachment-empty-array.fix       |  1 +
 .../object_validators/chat_message_validator.ex   |  5 +++++
 .../object_validators/chat_validation_test.exs    | 15 +++++++++++++++
 3 files changed, 21 insertions(+)
 create mode 100644 changelog.d/chat-attachment-empty-array.fix

diff --git a/changelog.d/chat-attachment-empty-array.fix b/changelog.d/chat-attachment-empty-array.fix
new file mode 100644
index 000000000..7d98c9dd2
--- /dev/null
+++ b/changelog.d/chat-attachment-empty-array.fix
@@ -0,0 +1 @@
+ChatMessage: Tolerate attachment field set to an empty array
diff --git a/lib/pleroma/web/activity_pub/object_validators/chat_message_validator.ex b/lib/pleroma/web/activity_pub/object_validators/chat_message_validator.ex
index efae48cae..09e25be89 100644
--- a/lib/pleroma/web/activity_pub/object_validators/chat_message_validator.ex
+++ b/lib/pleroma/web/activity_pub/object_validators/chat_message_validator.ex
@@ -57,6 +57,11 @@ def fix_attachment(%{"attachment" => [attachment | _]} = data) do
     |> Map.put("attachment", attachment)
   end
 
+  def fix_attachment(%{"attachment" => attachment} = data) when attachment == [] do
+    data
+    |> Map.drop(["attachment"])
+  end
+
   def fix_attachment(data), do: data
 
   def changeset(struct, data) do
diff --git a/test/pleroma/web/activity_pub/object_validators/chat_validation_test.exs b/test/pleroma/web/activity_pub/object_validators/chat_validation_test.exs
index 812944452..301fed60d 100644
--- a/test/pleroma/web/activity_pub/object_validators/chat_validation_test.exs
+++ b/test/pleroma/web/activity_pub/object_validators/chat_validation_test.exs
@@ -147,6 +147,21 @@ test "validates for a basic object with an attachment but without content", %{
       assert object["attachment"]
     end
 
+    test "validates for a basic object with content but attachment set to empty array", %{
+      user: user,
+      recipient: recipient
+    } do
+      {:ok, valid_chat_message, _} = Builder.chat_message(user, recipient.ap_id, "Hello!")
+
+      valid_chat_message =
+        valid_chat_message
+        |> Map.put("attachment", [])
+
+      assert {:ok, object, _meta} = ObjectValidator.validate(valid_chat_message, [])
+
+      assert object == Map.drop(valid_chat_message, ["attachment"])
+    end
+
     test "does not validate if the message has no content", %{
       valid_chat_message: valid_chat_message
     } do