Plain text SQL Interrupted errors in JSON responses

The SQL time limit error embedded an HTML fragment (paragraph, textarea
and script tags) as the error string in JSON responses. DatasetteError
now accepts a plain_message which the exception handler prefers for
JSON error bodies; the HTML error page keeps the rich message with the
SQL textarea.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GrHZSypDfMnym1tM5XJAFZ

datasette/views/base.py

@@ -29,12 +29,15 @@ class DatasetteError(Exception):
         status=500,
         template=None,
         message_is_html=False,
+        plain_message=None,
     ):
         self.message = message
         self.title = title
         self.error_dict = error_dict or {}
         self.status = status
         self.message_is_html = message_is_html
+        # Plain text used for JSON error responses when message is HTML
+        self.plain_message = plain_message
 
 
 class View:

datasette/views/database.py

@@ -819,6 +819,10 @@ class QueryView(View):
                     title="SQL Interrupted",
                     status=400,
                     message_is_html=True,
+                    plain_message=(
+                        "SQL query took too long. The time limit is"
+                        " controlled by the sql_time_limit_ms setting."
+                    ),
                 )
             except sqlite3.DatabaseError as ex:
                 query_error = str(ex)

datasette/views/row.py

@@ -200,6 +200,10 @@ class RowView(BaseView):
                 title="SQL Interrupted",
                 status=400,
                 message_is_html=True,
+                plain_message=(
+                    "SQL query took too long. The time limit is"
+                    " controlled by the sql_time_limit_ms setting."
+                ),
             )
         except (sqlite3.OperationalError, InvalidSql) as e:
             raise DatasetteError(str(e), title="Invalid SQL", status=400)