Add column_details JSON extra

datasette/views/table_extras.py

@@ -1,6 +1,7 @@
 import itertools
 from dataclasses import dataclass
 
+from datasette.column_types import SQLiteType
 from datasette.database import QueryInterrupted
 from datasette.extras import Extra, ExtraExample, ExtraRegistry, ExtraScope, Provider
 from datasette.plugins import pm
@@ -342,6 +343,41 @@ class PrimaryKeysExtra(Extra):
         return context.pks
 
 
+def column_detail_as_json(column):
+    return {
+        "type": column.type,
+        "sqlite_type": SQLiteType.from_declared_type(column.type).value,
+        "notnull": column.notnull,
+        "default": column.default_value,
+        "is_pk": bool(column.is_pk),
+        "hidden": bool(column.hidden),
+    }
+
+
+class ColumnDetailsExtra(Extra):
+    description = (
+        "SQLite schema details for columns in this table. The dictionary maps "
+        "column names to ``type``, ``sqlite_type``, ``notnull``, ``default``, "
+        "``is_pk`` and ``hidden`` values."
+    )
+    example = ExtraExample("/fixtures/binary_data.json?_size=0&_extra=column_details")
+    examples = {
+        ExtraScope.ROW: ExtraExample(
+            "/fixtures/binary_data/1.json?_extra=column_details"
+        )
+    }
+    scopes = {ExtraScope.TABLE, ExtraScope.ROW}
+
+    async def resolve(self, context):
+        column_details = await context.datasette._get_resource_column_details(
+            context.database_name, context.table_name
+        )
+        return {
+            column_name: column_detail_as_json(column)
+            for column_name, column in column_details.items()
+        }
+
+
 class ActionsExtra(Extra):
     description = 'Async callable returning table or view actions made available by core and plugin hooks. Each item is either a link with ``href``, ``label`` and optional ``description`` keys, or a button with ``type: "button"``, ``label``, optional ``description`` and optional ``attrs``. See :ref:`plugin_actions`, :ref:`plugin_hook_table_actions` and :ref:`plugin_hook_view_actions`.'
     scopes = {ExtraScope.TABLE}
@@ -1206,6 +1242,7 @@ TABLE_EXTRA_CLASSES = [
     ColumnsExtra,
     AllColumnsExtra,
     PrimaryKeysExtra,
+    ColumnDetailsExtra,
     DisplayColumnsAndRowsProvider,
     DisplayColumnsExtra,
     DisplayRowsExtra,

docs/changelog.rst

@@ -4,6 +4,13 @@
 Changelog
 =========
 
+.. _v1_0_a36:
+
+1.0a36 (in development)
+-----------------------
+
+- The table and row JSON APIs now support ``?_extra=column_details`` for returning SQLite schema details for columns, including declared type, SQLite affinity, primary key, ``NOT NULL``, default and hidden-column metadata.
+
 .. _v1_0_a35:
 
 1.0a35 (2026-06-23)

docs/json_api.rst

@@ -402,6 +402,24 @@ The available table extras are listed below.
           "pk"
         ]
 
+``column_details``
+    SQLite schema details for columns in this table. The dictionary maps column names to ``type``, ``sqlite_type``, ``notnull``, ``default``, ``is_pk`` and ``hidden`` values.
+
+    ``GET /fixtures/binary_data.json?_size=0&_extra=column_details``
+
+    .. code-block:: json
+
+        {
+          "data": {
+            "type": "BLOB",
+            "sqlite_type": "BLOB",
+            "notnull": 0,
+            "default": null,
+            "is_pk": false,
+            "hidden": false
+          }
+        }
+
 ``display_columns``
     Column metadata used by the HTML table display. Each item includes ``name``, ``sortable``, ``is_pk``, ``type``, ``notnull``, ``description``, ``column_type`` and ``column_type_config`` keys.
 
@@ -807,6 +825,24 @@ The following extras are available for row JSON responses.
           "id"
         ]
 
+``column_details``
+    SQLite schema details for columns in this table. The dictionary maps column names to ``type``, ``sqlite_type``, ``notnull``, ``default``, ``is_pk`` and ``hidden`` values.
+
+    ``GET /fixtures/binary_data/1.json?_extra=column_details``
+
+    .. code-block:: json
+
+        {
+          "data": {
+            "type": "BLOB",
+            "sqlite_type": "BLOB",
+            "notnull": 0,
+            "default": null,
+            "is_pk": false,
+            "hidden": false
+          }
+        }
+
 ``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.)
 

tests/test_api.py

@@ -429,7 +429,7 @@ async def test_row_foreign_key_tables(ds_client):
 @pytest.mark.asyncio
 async def test_row_extras(ds_client):
     response = await ds_client.get(
-        "/fixtures/simple_primary_key/1.json?_extra=database,table,primary_keys,query,request,debug,foreign_key_tables"
+        "/fixtures/simple_primary_key/1.json?_extra=database,table,primary_keys,query,request,debug,foreign_key_tables,column_details"
     )
     assert response.status_code == 200
     data = response.json()
@@ -446,6 +446,40 @@ async def test_row_extras(ds_client):
         "format": "json",
     }
     assert len(data["foreign_key_tables"]) == 5
+    assert data["column_details"]["id"] == {
+        "type": "INTEGER",
+        "sqlite_type": "INTEGER",
+        "notnull": 0,
+        "default": None,
+        "is_pk": True,
+        "hidden": False,
+    }
+    assert data["column_details"]["content"] == {
+        "type": "TEXT",
+        "sqlite_type": "TEXT",
+        "notnull": 0,
+        "default": None,
+        "is_pk": False,
+        "hidden": False,
+    }
+
+
+@pytest.mark.asyncio
+async def test_column_details_extra_row_for_null_blob(ds_client):
+    response = await ds_client.get(
+        "/fixtures/binary_data/3.json?_extra=column_details"
+    )
+    assert response.status_code == 200
+    assert response.json()["column_details"] == {
+        "data": {
+            "type": "BLOB",
+            "sqlite_type": "BLOB",
+            "notnull": 0,
+            "default": None,
+            "is_pk": False,
+            "hidden": False,
+        }
+    }
 
 
 @pytest.mark.asyncio

tests/test_table_api.py

@@ -1336,6 +1336,47 @@ async def test_binary_data_in_json(ds_client, path, expected_json, expected_text
         assert response.text == expected_text
 
 
+@pytest.mark.asyncio
+async def test_column_details_extra_table(ds_client):
+    response = await ds_client.get(
+        "/fixtures/binary_data.json?_size=0&_extra=column_details"
+    )
+    assert response.status_code == 200
+    assert response.json()["column_details"] == {
+        "data": {
+            "type": "BLOB",
+            "sqlite_type": "BLOB",
+            "notnull": 0,
+            "default": None,
+            "is_pk": False,
+            "hidden": False,
+        }
+    }
+
+    response = await ds_client.get(
+        "/fixtures/simple_primary_key.json?_size=0&_extra=column_details"
+    )
+    assert response.status_code == 200
+    assert response.json()["column_details"] == {
+        "id": {
+            "type": "INTEGER",
+            "sqlite_type": "INTEGER",
+            "notnull": 0,
+            "default": None,
+            "is_pk": True,
+            "hidden": False,
+        },
+        "content": {
+            "type": "TEXT",
+            "sqlite_type": "TEXT",
+            "notnull": 0,
+            "default": None,
+            "is_pk": False,
+            "hidden": False,
+        },
+    }
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     "qs",