community: Correctly handle multi-element rich text (langchain-ai#25762)

**Description:**

- Add _concatenate_rich_text method to combine all elements in rich text
arrays
- Update load_page method to use _concatenate_rich_text for rich text
properties
- Ensure all text content is captured, including inline code and
formatted text
- Add unit tests to verify correct handling of multi-element rich text
This fix prevents truncation of content after backticks or other
formatting elements.

 **Issue:**

Using Notion DB Loader, the text for `richtext` and `title` is truncated
after 1st element was loaded as Notion Loader only read the first
element.

**Dependencies:** any dependencies required for this change
None.

---------

Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>
Co-authored-by: Erick Friis <erick@langchain.dev>

libs/community/langchain_community/document_loaders/notiondb.py

@@ -107,19 +107,15 @@ def load_page(self, page_summary: Dict[str, Any]) -> Document:
         # load properties as metadata
         metadata: Dict[str, Any] = {}
 
+        value: Any
+
         for prop_name, prop_data in page_summary["properties"].items():
             prop_type = prop_data["type"]
 
             if prop_type == "rich_text":
-                value = (
-                    prop_data["rich_text"][0]["plain_text"]
-                    if prop_data["rich_text"]
-                    else None
-                )
+                value = self._concatenate_rich_text(prop_data["rich_text"])
             elif prop_type == "title":
-                value = (
-                    prop_data["title"][0]["plain_text"] if prop_data["title"] else None
-                )
+                value = self._concatenate_rich_text(prop_data["title"])
             elif prop_type == "multi_select":
                 value = (
                     [item["name"] for item in prop_data["multi_select"]]
@@ -228,3 +224,7 @@ def _request(
         )
         res.raise_for_status()
         return res.json()
+
+    def _concatenate_rich_text(self, rich_text_array: List[Dict[str, Any]]) -> str:
+        """Concatenate all text content from a rich_text array."""
+        return "".join(item["plain_text"] for item in rich_text_array)

libs/community/tests/unit_tests/document_loaders/test_notiondb_loader.py

@@ -0,0 +1,138 @@
+from unittest.mock import Mock, patch
+
+from langchain_core.documents import Document
+
+from langchain_community.document_loaders import NotionDBLoader
+
+
+class TestNotionDBLoader:
+    def setup_method(self) -> None:
+        self.loader = NotionDBLoader(
+            integration_token="fake_token", database_id="fake_db_id"
+        )
+
+    def test_concatenate_rich_text(self) -> None:
+        # Setup
+        rich_text = [
+            {"plain_text": "Hello "},
+            {"plain_text": "world"},
+            {"plain_text": "!"},
+        ]
+
+        # Exercise
+        result = self.loader._concatenate_rich_text(rich_text)
+
+        # Assert
+        assert result == "Hello world!"
+
+    @patch("langchain_community.document_loaders.notiondb.NotionDBLoader._request")
+    @patch("langchain_community.document_loaders.notiondb.NotionDBLoader._load_blocks")
+    def test_load_page_with_rich_text(
+        self, mock_load_blocks: Mock, mock_request: Mock
+    ) -> None:
+        # Setup
+        mock_load_blocks.return_value = "Mocked block content"
+        page_summary = {
+            "id": "page_id",
+            "properties": {
+                "Title": {"type": "title", "title": [{"plain_text": "Test Title"}]},
+                "Description": {
+                    "type": "rich_text",
+                    "rich_text": [
+                        {"plain_text": "This is "},
+                        {"plain_text": "a test"},
+                        {"plain_text": " description"},
+                    ],
+                },
+            },
+        }
+        expected_doc = Document(
+            page_content="Mocked block content",
+            metadata={
+                "title": "Test Title",
+                "description": "This is a test description",
+                "id": "page_id",
+            },
+        )
+
+        # Exercise
+        result = self.loader.load_page(page_summary)
+
+        # Assert
+        assert result == expected_doc
+
+    @patch("langchain_community.document_loaders.notiondb.NotionDBLoader._request")
+    @patch("langchain_community.document_loaders.notiondb.NotionDBLoader._load_blocks")
+    def test_load_page_with_code_in_rich_text(
+        self, mock_load_blocks: Mock, mock_request: Mock
+    ) -> None:
+        # Setup
+        mock_load_blocks.return_value = "Mocked block content"
+        page_summary = {
+            "id": "page_id",
+            "properties": {
+                "Answer": {
+                    "type": "rich_text",
+                    "rich_text": [
+                        {"plain_text": "Use "},
+                        {"plain_text": "print('Hello')"},
+                        {"plain_text": " to display text"},
+                    ],
+                }
+            },
+        }
+        expected_doc = Document(
+            page_content="Mocked block content",
+            metadata={"answer": "Use print('Hello') to display text", "id": "page_id"},
+        )
+
+        # Exercise
+        result = self.loader.load_page(page_summary)
+
+        # Assert
+        assert result == expected_doc
+
+    @patch("langchain_community.document_loaders.notiondb.NotionDBLoader._request")
+    @patch("langchain_community.document_loaders.notiondb.NotionDBLoader._load_blocks")
+    def test_load(self, mock_load_blocks: Mock, mock_request: Mock) -> None:
+        # Setup
+        mock_load_blocks.return_value = "Mocked block content"
+        mock_request.return_value = {
+            "results": [
+                {
+                    "id": "page_id_1",
+                    "properties": {
+                        "Title": {
+                            "type": "title",
+                            "title": [{"plain_text": "Test Title 1"}],
+                        }
+                    },
+                },
+                {
+                    "id": "page_id_2",
+                    "properties": {
+                        "Title": {
+                            "type": "title",
+                            "title": [{"plain_text": "Test Title 2"}],
+                        }
+                    },
+                },
+            ],
+            "has_more": False,
+        }
+        expected_docs = [
+            Document(
+                page_content="Mocked block content",
+                metadata={"title": "Test Title 1", "id": "page_id_1"},
+            ),
+            Document(
+                page_content="Mocked block content",
+                metadata={"title": "Test Title 2", "id": "page_id_2"},
+            ),
+        ]
+
+        # Exercise
+        result = self.loader.load()
+
+        # Assert
+        assert result == expected_docs