Row JSON: drop truncated, render_cell is a single object

The default row shape no longer includes "truncated", since a single row
lookup cannot be truncated, and ?_extra=render_cell returns one object to
match "row". With a ?_shape= both behave as they do for tables.

Refs #2612

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GaqG8H8ajwxizKXdbGrtve

datasette/renderer.py

@@ -58,7 +58,8 @@ def json_renderer(request, args, data, error, truncated=None, view_name=None):
         status_code = 400
         data.update(error_body(error, status_code))
 
-    if truncated is not None:
+    # A single row lookup cannot be truncated
+    if truncated is not None and not single_row:
         data["truncated"] = truncated
     if shape == "arrayfirst":
         # Rows can be dicts, sqlite3.Row or lists (from remove_infinites)
@@ -78,6 +79,10 @@ def json_renderer(request, args, data, error, truncated=None, view_name=None):
                 ("row", row) if key == "rows" else (key, value)
                 for key, value in data.items()
             )
+            # Likewise the render_cell extra becomes a single object
+            if "render_cell" in data:
+                cells = data["render_cell"]
+                data["render_cell"] = cells[0] if cells else {}
         if shape == "object":
             shape_error = None
             if "primary_keys" not in data:

datasette/views/table_extras.py

@@ -648,12 +648,13 @@ class RenderCellExtra(Extra):
         ExtraScope.ROW: ExtraExample(
             value={
                 "row": {"id": 4, "content": "RENDER_CELL_DEMO"},
-                "render_cell": [{"content": "<strong>Custom rendered HTML</strong>"}],
+                "render_cell": {"content": "<strong>Custom rendered HTML</strong>"},
             },
             note=(
-                "The ``render_cell`` array has one item for the requested row. "
-                "The object is keyed by column name. Only columns whose rendered "
-                "value differs from the default are included."
+                "The ``render_cell`` object is keyed by column name. Only columns "
+                "whose rendered value differs from the default are included. If a "
+                "``?_shape=`` is specified ``render_cell`` is instead a list with "
+                "one item, matching the ``rows`` list."
             ),
         ),
         ExtraScope.QUERY: ExtraExample(

docs/json_api.rst

@@ -960,7 +960,7 @@ The following extras are available for row JSON responses.
 ``render_cell``
     Rendered HTML for each cell using the render_cell plugin hook (See the :ref:`render_cell() plugin hook <plugin_hook_render_cell>` documentation.)
 
-    The ``render_cell`` array has one item for the requested row. The object is keyed by column name. Only columns whose rendered value differs from the default are included.
+    The ``render_cell`` object is keyed by column name. Only columns whose rendered value differs from the default are included. If a ``?_shape=`` is specified ``render_cell`` is instead a list with one item, matching the ``rows`` list.
 
     .. code-block:: json
 
@@ -969,11 +969,9 @@ The following extras are available for row JSON responses.
             "id": 4,
             "content": "RENDER_CELL_DEMO"
           },
-          "render_cell": [
-            {
-              "content": "<strong>Custom rendered HTML</strong>"
-            }
-          ]
+          "render_cell": {
+            "content": "<strong>Custom rendered HTML</strong>"
+          }
         }
 
 ``debug``

tests/test_api.py

@@ -369,6 +369,7 @@ async def test_row(ds_client):
     assert data["ok"] is True
     assert data["row"] == {"id": 1, "content": "hello"}
     assert "rows" not in data
+    assert "truncated" not in data
 
 
 @pytest.mark.asyncio
@@ -391,6 +392,7 @@ async def test_row_shape(ds_client, shape, expected):
     data = response.json()
     if shape in ("objects", "arrays"):
         assert "row" not in data
+        assert data["truncated"] is False
         data = data["rows"]
     assert data == expected
 
@@ -650,20 +652,23 @@ async def test_row_extra_render_cell():
         assert "render_cell" in data
         assert "row" in data
 
-        # render_cell should be a list with one row (since this is a row page)
+        # render_cell is a single object to match "row"
         # Only columns modified by plugins are included (sparse output)
-        render_cell = data["render_cell"]
-        assert len(render_cell) == 1
-
-        # The row: id=1, name='Alice'
         # The 'name' column should be rendered by our plugin as <strong>Alice</strong>
-        assert render_cell[0]["name"] == "<strong>Alice</strong>"
         # The 'id' column is not included since no plugin modified it
-        assert "id" not in render_cell[0]
+        assert data["render_cell"] == {"name": "<strong>Alice</strong>"}
 
         # The regular row should still contain raw values
         assert data["row"] == {"id": 1, "name": "Alice"}
 
+        # With a ?_shape= render_cell is a list, matching "rows"
+        response = await ds.client.get(
+            "/test_row_render/test_render/1.json?_extra=render_cell&_shape=objects"
+        )
+        data = response.json()
+        assert data["render_cell"] == [{"name": "<strong>Alice</strong>"}]
+        assert data["rows"] == [{"id": 1, "name": "Alice"}]
+
     finally:
         ds.pm.unregister(name="TestRenderCellPlugin")
 

tests/test_column_types.py

@@ -748,7 +748,7 @@ async def test_row_endpoint_render_cell_with_column_types(ds_ct):
     response = await ds_ct.client.get("/data/posts/1.json?_extra=render_cell")
     assert response.status_code == 200
     data = response.json()
-    rendered = data["render_cell"][0]
+    rendered = data["render_cell"]
     assert "mailto:" in rendered["author_email"]
     assert "href" in rendered["website"]