Add tests for showing DataFrames with no rows and improve output messages

Author: kosiew

python/tests/test_dataframe.py

@@ -2665,31 +2665,17 @@ def trigger_interrupt():
     # Make sure the interrupt thread has finished
     interrupt_thread.join(timeout=1.0)
 
+def test_show_select_where_no_rows(capsys) -> None:
+    ctx = SessionContext()
+    df = ctx.sql("SELECT 1 WHERE 1=0")
+    df.show()
+    out = capsys.readouterr().out
+    assert "DataFrame has no rows" in out
 
-def test_show_from_empty_rows(capsys):
-    """Create a DataFrame with a valid schema but zero rows and call show().
-
-    This verifies that showing an empty-but-schema'd DataFrame does not panic
-    and prints a helpful message instead.
-    """
-    # duplicate of test_show_empty; covered elsewhere
-    pass
-
-
-def test_select_where_no_rows(capsys):
-    """Create a DataFrame a:[1,2,3], filter with a>4 to produce zero rows and call show().
-
-    This verifies that a query returning zero rows does not trigger a panic and
-    instead prints a helpful message.
-    """
-    # duplicate of test_show_empty; covered elsewhere
-    pass
-
-
-def test_sql_select_where_no_rows(capsys):
-    """Register a table 't' with a:[1,2,3], run SQL that returns no rows, and call show().
 
-    Ensures SQL path that returns zero rows doesn't panic when showing results.
-    """
-    # duplicate of test_show_empty; covered elsewhere
-    pass
+def test_show_from_empty_batch(capsys) -> None:
+    ctx = SessionContext()
+    batch = pa.record_batch([pa.array([], type=pa.int32())], names=["a"])
+    ctx.create_dataframe([[batch]]).show()
+    out = capsys.readouterr().out
+    assert "| a |" in out