show/hide link for SQL on custom query page

Closes #415

datasette/templates/query.html

@@ -26,11 +26,13 @@
 {% block description_source_license %}{% include "_description_source_license.html" %}{% endblock %}
 
 <form class="sql" action="/{{ database }}-{{ database_hash }}{% if canned_query %}/{{ canned_query }}{% endif %}" method="get">
-    <h3>Custom SQL query{% if display_rows %} returning {% if truncated %}more than {% endif %}{{ "{:,}".format(display_rows|length) }} row{% if display_rows|length == 1 %}{% else %}s{% endif %}{% endif %}</h3>
-    {% if editable and config.allow_sql %}
-        <p><textarea name="sql">{% if query and query.sql %}{{ query.sql }}{% else %}select * from {{ tables[0].name|escape_sqlite }}{% endif %}</textarea></p>
-    {% else %}
-        <pre>{% if query %}{{ query.sql }}{% endif %}</pre>
+    <h3>Custom SQL query{% if display_rows %} returning {% if truncated %}more than {% endif %}{{ "{:,}".format(display_rows|length) }} row{% if display_rows|length == 1 %}{% else %}s{% endif %}{% endif %} <span class="show-hide-sql">{% if hide_sql %}(<a href="{{ path_with_removed_args(request, {'_hide_sql': '1'}) }}">show</a>){% else %}(<a href="{{ path_with_added_args(request, {'_hide_sql': '1'}) }}">hide</a>){% endif %}</span></h3>
+    {% if not hide_sql %}
+        {% if editable and config.allow_sql %}
+            <p><textarea name="sql">{% if query and query.sql %}{{ query.sql }}{% else %}select * from {{ tables[0].name|escape_sqlite }}{% endif %}</textarea></p>
+        {% else %}
+            <pre>{% if query %}{{ query.sql }}{% endif %}</pre>
+        {% endif %}
     {% endif %}
     {% if named_parameter_values %}
         <h3>Query parameters</h3>

datasette/views/base.py

@@ -23,6 +23,7 @@ from datasette.utils import (
     is_url,
     path_from_row_pks,
     path_with_added_args,
+    path_with_removed_args,
     path_with_format,
     remove_infinites,
     resolve_table_and_format,
@@ -578,6 +579,10 @@ class BaseView(RenderMixin):
                 "canned_query": canned_query,
                 "metadata": metadata,
                 "config": self.ds.config_dict(),
+                "request": request,
+                "path_with_added_args": path_with_added_args,
+                "path_with_removed_args": path_with_removed_args,
+                "hide_sql": "_hide_sql" in params,
             }
 
         return {

tests/test_html.py

@@ -824,3 +824,22 @@ def test_urlify_custom_queries(app_client):
   https://twitter.com/simonw
  </a>
 </td>''' == soup.find("td", {"class": "col-user_url"}).prettify().strip()
+
+
+def test_show_hide_sql_query(app_client):
+    path = "/fixtures?" + urllib.parse.urlencode({
+        "sql": "select ('https://twitter.com/' || 'simonw') as user_url;"
+    })
+    response = app_client.get(path)
+    soup = Soup(response.body, "html.parser")
+    span = soup.select(".show-hide-sql")[0]
+    assert span.find("a")["href"].endswith("&_hide_sql=1")
+    assert "(hide)" == span.getText()
+    assert soup.find("textarea") is not None
+    # Now follow the link to hide it
+    response = app_client.get(span.find("a")["href"])
+    soup = Soup(response.body, "html.parser")
+    span = soup.select(".show-hide-sql")[0]
+    assert not span.find("a")["href"].endswith("&_hide_sql=1")
+    assert "(show)" == span.getText()
+    assert soup.find("textarea") is None