Added message for associations tab with one column in TableReport (#2094)

Co-authored-by: Jérôme Dockès <jerome@dockes.org>

Author: AlicjaKo

CHANGES.rst

@@ -25,6 +25,8 @@ Changes
 - An unnecessary warning that was raised when passing a numpy array to the
   TableVectorizer has been removed. :pr:`1908` by
   :user:`Sandrine Henry <sandrineh>`.
+- Improving the association tab error message when only one column is present
+  :pr:`2094` by :user:`Alicja Kosak <AlicjaKo>`.
 
 Bugfixes
 --------

skrub/_reporting/_data/templates/column-associations.html

@@ -79,7 +79,10 @@
         In this case, one of them may be redundant and for some models (such as linear models) it might be beneficial to remove it.
     </div>
 
+    {% elif summary['n_columns'] == 1 %}
+    No associations were computed because the dataframe has only one column.
     {% else %}
     No strong associations between any pair of columns were identified by a quick screening of a subsample of the dataframe.
     {% endif %}
+
 </article>

skrub/_reporting/tests/test_table_report.py

@@ -443,6 +443,10 @@ def test_single_column_report(df_module):
     col_name = sbd.name(single_col)
     html = report.html()
     assert col_name in html
+    assert (
+        "No associations were computed because the dataframe has only one "
+        "column." in html
+    )
 
 
 def test_error_make_table():