Show more useful error message for SQL interrupted, closes #142

datasette/app.py

@@ -12,6 +12,7 @@ import urllib.parse
 from concurrent import futures
 from pathlib import Path
 
+from markupsafe import Markup
 import pluggy
 from jinja2 import ChoiceLoader, Environment, FileSystemLoader, PrefixLoader
 from sanic import Sanic, response
@@ -461,6 +462,7 @@ class Datasette:
         @app.exception(Exception)
         def on_exception(request, exception):
             title = None
+            help = None
             if isinstance(exception, NotFound):
                 status = 404
                 info = {}
@@ -473,6 +475,8 @@ class Datasette:
                 status = exception.status
                 info = exception.error_dict
                 message = exception.message
+                if exception.messagge_is_html:
+                    message = Markup(message)
                 title = exception.title
             else:
                 status = 500

datasette/views/base.py

@@ -27,11 +27,12 @@ HASH_LENGTH = 7
 
 class DatasetteError(Exception):
 
-    def __init__(self, message, title=None, error_dict=None, status=500, template=None):
+    def __init__(self, message, title=None, error_dict=None, status=500, template=None, messagge_is_html=False):
         self.message = message
         self.title = title
         self.error_dict = error_dict or {}
         self.status = status
+        self.messagge_is_html = messagge_is_html
 
 
 class RenderMixin(HTTPMethodView):
@@ -154,7 +155,11 @@ class BaseView(RenderMixin):
             else:
                 data, extra_template_data, templates = response_or_template_contexts
         except InterruptedError as e:
-            raise DatasetteError(str(e), title="SQL Interrupted", status=400)
+            raise DatasetteError("""
+                SQL query took too long. The time limit is controlled by the
+                <a href="https://datasette.readthedocs.io/en/stable/config.html#sql-time-limit-ms">sql_time_limit_ms</a>
+                configuration option.
+            """, title="SQL Interrupted", status=400, messagge_is_html=True)
         except (sqlite3.OperationalError, InvalidSql) as e:
             raise DatasetteError(str(e), title="Invalid SQL", status=400)
 

tests/test_html.py

@@ -1,10 +1,11 @@
 from bs4 import BeautifulSoup as Soup
-from .fixtures import app_client
+from .fixtures import app_client, app_client_shorter_time_limit
 import pytest
 import re
 import urllib.parse
 
 pytest.fixture(scope='session')(app_client)
+pytest.fixture(scope='session')(app_client_shorter_time_limit)
 
 
 def test_homepage(app_client):
@@ -29,6 +30,18 @@ def test_invalid_custom_sql(app_client):
     assert 'Statement must be a SELECT' in response.text
 
 
+def test_sql_time_limit(app_client_shorter_time_limit):
+    response = app_client_shorter_time_limit.get(
+        '/test_tables?sql=select+sleep(0.5)',
+        gather_request=False
+    )
+    assert 400 == response.status
+    expected_html_fragment = """
+        <a href="https://datasette.readthedocs.io/en/stable/config.html#sql-time-limit-ms">sql_time_limit_ms</a>
+    """.strip()
+    assert expected_html_fragment in response.text
+
+
 def test_view(app_client):
     response = app_client.get('/test_tables/simple_view', gather_request=False)
     assert response.status == 200