Chore: Structured consume task return values (#12612)

src/documents/serialisers.py

@@ -2477,7 +2477,6 @@ class TaskSerializerV10(OwnedObjectSerializer):
             "wait_time_seconds",
             "input_data",
             "result_data",
-            "result_message",
             "related_document_ids",
             "acknowledged",
             "owner",
@@ -2504,12 +2503,8 @@ class TaskSerializerV9(serializers.ModelSerializer):
     # v9 field: status -> uppercase Celery state strings
     status = serializers.SerializerMethodField()
 
-    # v9 field: result -> result_message (with legacy format fallback)
-    result = serializers.CharField(
-        source="result_message",
-        read_only=True,
-        allow_null=True,
-    )
+    # v9 field: result -> derived from result_data
+    result = serializers.SerializerMethodField()
 
     # v9 field: related_document -> first document ID from result_data
     related_document = serializers.SerializerMethodField()
@@ -2541,6 +2536,20 @@ class TaskSerializerV9(serializers.ModelSerializer):
         PaperlessTask.TaskType.LLM_INDEX: "llmindex_update",
     }
 
+    def get_result(self, obj: PaperlessTask) -> str | None:
+        """Reconstruct a human-readable result string from result_data for v9 clients."""
+        if not obj.result_data:
+            return None
+        if doc_id := obj.result_data.get("document_id"):
+            return f"Success. New document id {doc_id} created"
+        if reason := obj.result_data.get("reason"):
+            return reason
+        if dup_id := obj.result_data.get("duplicate_of"):
+            return f"Not consuming: It is a duplicate of document #{dup_id}"
+        if error := obj.result_data.get("error_message"):
+            return error
+        return None
+
     def get_task_name(self, obj: PaperlessTask) -> str:
         return self._TASK_TYPE_TO_V9_NAME.get(obj.task_type, obj.task_type)