?_trace=1 now depends on trace_debug setting, closes #1359

.github/workflows/deploy-latest.yml

@@ -53,7 +53,7 @@ jobs:
             --plugins-dir=plugins \
             --branch=$GITHUB_SHA \
             --version-note=$GITHUB_SHA \
-            --extra-options="--setting template_debug 1 --crossdb" \
+            --extra-options="--setting template_debug 1 --setting trace_debug 1 --crossdb" \
             --install=pysqlite3-binary \
             --service=datasette-latest
         # Deploy docs.db to a different service

datasette/app.py

@@ -162,6 +162,11 @@ SETTINGS = (
         False,
         "Allow display of template debug information with ?_context=1",
     ),
+    Setting(
+        "trace_debug",
+        False,
+        "Allow display of SQL trace debug information with ?_trace=1",
+    ),
     Setting("base_url", "/", "Datasette URLs should use this base path"),
 )
 
@@ -1041,14 +1046,15 @@ class Datasette:
                 if not database.is_mutable:
                     await database.table_counts(limit=60 * 60 * 1000)
 
+        asgi = asgi_csrf.asgi_csrf(
+            DatasetteRouter(self, routes),
+            signing_secret=self._secret,
+            cookie_name="ds_csrftoken",
+        )
+        if self.setting("trace_debug"):
+            asgi = AsgiTracer(asgi)
         asgi = AsgiLifespan(
-            AsgiTracer(
-                asgi_csrf.asgi_csrf(
-                    DatasetteRouter(self, routes),
-                    signing_secret=self._secret,
-                    cookie_name="ds_csrftoken",
-                )
-            ),
+            asgi,
             on_startup=setup_db,
         )
         for wrapper in pm.hook.asgi_wrapper(datasette=self):

docs/json_api.rst

@@ -206,6 +206,16 @@ query string arguments:
     For how many seconds should this response be cached by HTTP proxies? Use
     ``?_ttl=0`` to disable HTTP caching entirely for this request.
 
+``?_trace=1``
+    Turns on tracing for this page: SQL queries executed during the request will
+    be gathered and included in the response, either in a new ``"_traces"`` key
+    for JSON responses or at the bottom of the page if the response is in HTML.
+
+    The structure of the data returned here should be considered highly unstable
+    and very likely to change.
+
+    Only available if the :ref:`setting_trace_debug` setting is enabled.
+
 .. _table_arguments:
 
 Table arguments
@@ -389,14 +399,6 @@ Special table arguments
 ``?_nocount=1``
     Disable the ``select count(*)`` query used on this page - a count of ``None`` will be returned instead.
 
-``?_trace=1``
-    Turns on tracing for this page: SQL queries executed during the request will
-    be gathered and included in the response, either in a new ``"_traces"`` key
-    for JSON responses or at the bottom of the page if the response is in HTML.
-
-    The structure of the data returned here should be considered highly unstable
-    and very likely to change.
-
 .. _expand_foreign_keys:
 
 Expanding foreign key references

docs/settings.rst

@@ -286,6 +286,22 @@ Some examples:
 * https://latest.datasette.io/fixtures?_context=1
 * https://latest.datasette.io/fixtures/roadside_attractions?_context=1
 
+.. _setting_trace_debug:
+
+trace_debug
+~~~~~~~~~~~
+
+This setting enables appending ``?_trace=1`` to any page in order to see the SQL queries and other trace information that was used to generate that page.
+
+Enable it like this::
+
+    datasette mydatabase.db --setting trace_debug 1
+
+Some examples:
+
+* https://latest.datasette.io/?_trace=1
+* https://latest.datasette.io/fixtures/roadside_attractions?_trace=1
+
 .. _setting_base_url:
 
 base_url

tests/fixtures.py

@@ -214,6 +214,12 @@ def app_client_with_hash():
         yield client
 
 
+@pytest.fixture(scope="session")
+def app_client_with_trace():
+    with make_app_client(config={"trace_debug": True}, is_immutable=True) as client:
+        yield client
+
+
 @pytest.fixture(scope="session")
 def app_client_shorter_time_limit():
     with make_app_client(20) as client:

tests/test_api.py

@@ -15,6 +15,7 @@ from .fixtures import (  # noqa
     app_client_conflicting_database_names,
     app_client_with_cors,
     app_client_with_dot,
+    app_client_with_trace,
     app_client_immutable_and_inspect_file,
     generate_compound_rows,
     generate_sortable_rows,
@@ -1422,6 +1423,7 @@ def test_settings_json(app_client):
         "force_https_urls": False,
         "hash_urls": False,
         "template_debug": False,
+        "trace_debug": False,
         "base_url": "/",
     } == response.json
 
@@ -1692,8 +1694,10 @@ def test_nocount(app_client, nocount, expected_count):
     assert response.json["filtered_table_rows_count"] == expected_count
 
 
-def test_nocount_nofacet_if_shape_is_object(app_client):
-    response = app_client.get("/fixtures/facetable.json?_trace=1&_shape=object")
+def test_nocount_nofacet_if_shape_is_object(app_client_with_trace):
+    response = app_client_with_trace.get(
+        "/fixtures/facetable.json?_trace=1&_shape=object"
+    )
     assert "count(*)" not in response.text
 
 
@@ -1863,9 +1867,17 @@ def test_custom_query_with_unicode_characters(app_client):
     assert [{"id": 1, "name": "San Francisco"}] == response.json
 
 
-def test_trace(app_client):
-    response = app_client.get("/fixtures/simple_primary_key.json?_trace=1")
+@pytest.mark.parametrize("trace_debug", (True, False))
+def test_trace(trace_debug):
+    with make_app_client(config={"trace_debug": trace_debug}) as client:
+        response = client.get("/fixtures/simple_primary_key.json?_trace=1")
+        assert response.status == 200
+
     data = response.json
+    if not trace_debug:
+        assert "_trace" not in data
+        return
+
     assert "_trace" in data
     trace_info = data["_trace"]
     assert isinstance(trace_info["request_duration_ms"], float)

tests/test_csv.py

@@ -3,6 +3,7 @@ from .fixtures import (  # noqa
     app_client,
     app_client_csv_max_mb_one,
     app_client_with_cors,
+    app_client_with_trace,
 )
 
 EXPECTED_TABLE_CSV = """id,content
@@ -160,8 +161,8 @@ def test_table_csv_stream(app_client):
     assert 1002 == len([b for b in response.body.split(b"\r\n") if b])
 
 
-def test_csv_trace(app_client):
-    response = app_client.get("/fixtures/simple_primary_key.csv?_trace=1")
+def test_csv_trace(app_client_with_trace):
+    response = app_client_with_trace.get("/fixtures/simple_primary_key.csv?_trace=1")
     assert response.headers["content-type"] == "text/html; charset=utf-8"
     soup = Soup(response.text, "html.parser")
     assert (
@@ -171,13 +172,13 @@ def test_csv_trace(app_client):
     assert "select id, content from simple_primary_key" in soup.find("pre").text
 
 
-def test_table_csv_stream_does_not_calculate_facets(app_client):
-    response = app_client.get("/fixtures/simple_primary_key.csv?_trace=1")
+def test_table_csv_stream_does_not_calculate_facets(app_client_with_trace):
+    response = app_client_with_trace.get("/fixtures/simple_primary_key.csv?_trace=1")
     soup = Soup(response.text, "html.parser")
     assert "select content, count(*) as n" not in soup.find("pre").text
 
 
-def test_table_csv_stream_does_not_calculate_counts(app_client):
-    response = app_client.get("/fixtures/simple_primary_key.csv?_trace=1")
+def test_table_csv_stream_does_not_calculate_counts(app_client_with_trace):
+    response = app_client_with_trace.get("/fixtures/simple_primary_key.csv?_trace=1")
     soup = Soup(response.text, "html.parser")
     assert "select count(*)" not in soup.find("pre").text