Pass defaultTable to the SQL editor from table-scoped pages

The table page's 'View and edit SQL' link now carries ?_table=<name>;
QueryView validates it against the actor-visible tables/views for the
database before exposing it as default_table, so the editor completes
that table's columns unprefixed. Stored/canned queries are unaffected.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

datasette/templates/_codemirror_foot.html

@@ -15,6 +15,9 @@
     if (sqlInput) {
       var editor = (window.editor = cm.editorFromTextArea(sqlInput, {
         schema,
+        {% if default_table is defined and default_table %}
+        defaultTable: {{ default_table|tojson }},
+        {% endif %}
       }));
       if (sqlFormat) {
         sqlFormat.addEventListener("click", (ev) => {

datasette/templates/table.html

@@ -126,7 +126,7 @@
 {% endif %}
 
 {% if query.sql and allow_execute_sql %}
-    <p><a class="not-underlined" title="{{ query.sql }}" href="{{ urls.database(database) }}?{{ {'sql': query.sql}|urlencode|safe }}{% if query.params %}&amp;{{ query.params|urlencode|safe }}{% endif %}">&#x270e; <span class="underlined">View and edit SQL</span></a></p>
+    <p><a class="not-underlined" title="{{ query.sql }}" href="{{ urls.database(database) }}?{{ {'sql': query.sql, '_table': table}|urlencode|safe }}{% if query.params %}&amp;{{ query.params|urlencode|safe }}{% endif %}">&#x270e; <span class="underlined">View and edit SQL</span></a></p>
 {% endif %}
 
 <p class="export-links">This data as {% for name, url in renderers.items() %}<a href="{{ url }}">{{ name }}</a>{{ ", " if not loop.last }}{% endfor %}{% if display_rows %}, <a href="{{ url_csv }}">CSV</a> (<a href="#export">advanced</a>){% endif %}</p>

datasette/views/database.py

@@ -457,6 +457,11 @@ class QueryContext(Context):
             "help": "Dictionary mapping table names to lists of column names, used to power SQL autocomplete."
         }
     )
+    default_table: str = field(
+        metadata={
+            "help": "Name of the focal table for this query, if any - set when the query page was reached from a table-scoped context (such as the table page's 'View and edit SQL' link) so the SQL editor can complete that table's columns unprefixed. ``None`` otherwise, including for stored/canned queries."
+        }
+    )
     alternate_url_json: str = field(
         metadata={"help": "URL for alternate JSON version of this page"}
     )
@@ -716,6 +721,15 @@ class QueryView(View):
         # Create lookup dict for quick access
         allowed_dict = {r.child: r for r in allowed_tables_page.resources}
 
+        # If the request carries a ?_table= pointing at a real (visible) table
+        # or view in this database, treat this as a table-scoped query - e.g.
+        # arriving here via the "View and edit SQL" link on a table page - so
+        # the SQL editor can offer that table's columns unprefixed. Anything
+        # else (including stored/canned queries, which may reference more
+        # than one table) leaves this as None.
+        requested_table = request.args.get("_table")
+        default_table = requested_table if requested_table in allowed_dict else None
+
         # Are we a stored query?
         stored_query = None
         stored_query_write = False
@@ -1101,6 +1115,7 @@ class QueryView(View):
                             if allow_execute_sql
                             else {}
                         ),
+                        default_table=default_table,
                         columns=columns,
                         renderers=renderers,
                         url_csv=datasette.urls.path(

docs/template_context.rst

@@ -168,6 +168,9 @@ The page for arbitrary SQL queries (/database/-/query?sql=...) and stored querie
 ``db_is_immutable`` - ``bool``
     Boolean indicating if this database is immutable
 
+``default_table`` - ``str``
+    Name of the focal table for this query, if any - set when the query page was reached from a table-scoped context (such as the table page's 'View and edit SQL' link) so the SQL editor can complete that table's columns unprefixed. ``None`` otherwise, including for stored/canned queries.
+
 ``display_rows`` - ``list``
     List of result rows formatted for HTML display. Each row is a list of rendered cell values in the same order as ``columns``.
 

tests/test_html.py

@@ -284,6 +284,53 @@ async def test_query_page_with_no_sql(ds_client):
     assert 'class="rows-and-columns"' not in response.text
 
 
+@pytest.mark.asyncio
+async def test_table_page_view_and_edit_sql_link_carries_table(ds_client):
+    # The table page's "View and edit SQL" link should point at the query
+    # page with a &_table= param identifying the focal table, so the SQL
+    # editor can offer that table's columns unprefixed.
+    response = await ds_client.get("/fixtures/facetable")
+    assert response.status_code == 200
+    soup = Soup(response.content, "html.parser")
+    link = soup.find("span", string="View and edit SQL").find_parent("a")
+    assert link is not None
+    assert "_table=facetable" in link["href"]
+
+
+@pytest.mark.asyncio
+async def test_query_page_default_table_from_table_scoped_link(ds_client):
+    # Following the table page's edit-SQL link should result in a query page
+    # whose SQL editor is initialized with defaultTable set to that table.
+    table_response = await ds_client.get("/fixtures/facetable")
+    soup = Soup(table_response.content, "html.parser")
+    href = soup.find("span", string="View and edit SQL").find_parent("a")["href"]
+    response = await ds_client.get(href, follow_redirects=True)
+    assert response.status_code == 200
+    assert 'defaultTable: "facetable"' in response.text
+
+
+@pytest.mark.asyncio
+async def test_query_page_no_default_table_without_table_scope(ds_client):
+    # The plain database query page (no focal table) should not set
+    # defaultTable at all.
+    response = await ds_client.get("/fixtures/-/query?sql=select+1")
+    assert response.status_code == 200
+    assert "defaultTable" not in response.text
+
+
+@pytest.mark.asyncio
+async def test_query_page_ignores_invalid_table_param(ds_client):
+    # A ?_table= value that isn't a real table/view in this database should
+    # not be reflected back into the page - and should not break execution
+    # of the query itself (leading-underscore params are not treated as SQL
+    # bind parameters unless they appear as :name in the SQL).
+    response = await ds_client.get(
+        "/fixtures/-/query?sql=select+1&_table=not_a_real_table"
+    )
+    assert response.status_code == 200
+    assert "defaultTable" not in response.text
+
+
 @pytest.mark.asyncio
 async def test_query_csv_with_no_sql_is_400(ds_client):
     # https://github.com/simonw/datasette/issues/2743