test_create_table_error_if_pk_changed, refs #1927

datasette/views/database.py

@@ -620,6 +620,7 @@ class TableCreateView(BaseView):
         if not self._table_name_re.match(table_name):
             return _error(["Invalid table name"])
 
+        table_exists = await db.table_exists(data["table"])
         columns = data.get("columns")
         rows = data.get("rows")
         row = data.get("row")
@@ -676,8 +677,17 @@ class TableCreateView(BaseView):
                     return _error(["pks must be a list of strings"])
 
         # If table exists already, read pks from that instead
-        if await db.table_exists(table_name):
+        if table_exists:
-            pks = await db.primary_keys(table_name)
+            actual_pks = await db.primary_keys(table_name)
+            # if pk passed and table already exists check it does not change
+            bad_pks = False
+            if len(actual_pks) == 1 and data.get("pk") and data["pk"] != actual_pks[0]:
+                bad_pks = True
+            elif len(actual_pks) > 1 and data.get("pks") and set(data["pks"]) != set(actual_pks):
+                bad_pks = True
+            if bad_pks:
+                return _error(["pk cannot be changed for existing table"])
+            pks = actual_pks
 
         def create_table(conn):
             table = sqlite_utils.Database(conn)[table_name]

tests/test_api_write.py

@@ -1199,6 +1199,43 @@ async def test_create_table_ignore_replace(ds_write, input, expected_rows_after)
     assert rows.json() == expected_rows_after
 
 
+@pytest.mark.asyncio
+async def test_create_table_error_if_pk_changed(ds_write):
+    token = write_token(ds_write)
+    first_response = await ds_write.client.post(
+        "/data/-/create",
+        json={
+            "rows": [{"id": 1, "name": "Row 1"}, {"id": 2, "name": "Row 2"}],
+            "table": "test_insert_replace",
+            "pk": "id",
+        },
+        headers={
+            "Authorization": "Bearer {}".format(token),
+            "Content-Type": "application/json",
+        },
+    )
+    assert first_response.status_code == 201
+    # Try a second time with a different pk
+    second_response = await ds_write.client.post(
+        "/data/-/create",
+        json={
+            "rows": [{"id": 1, "name": "Row 1"}, {"id": 2, "name": "Row 2"}],
+            "table": "test_insert_replace",
+            "pk": "name",
+            "replace": True,
+        },
+        headers={
+            "Authorization": "Bearer {}".format(token),
+            "Content-Type": "application/json",
+        },
+    )
+    assert second_response.status_code == 400
+    assert second_response.json() == {
+        "ok": False,
+        "errors": ["pk cannot be changed for existing table"],
+    }
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     "path",