fix: Throw exception if no header, body, or footer

Author: DenverCoder1

table2ascii/exceptions.py

@@ -128,6 +128,19 @@ def _message(self):
         )
 
 
+class NoHeaderBodyOrFooterError(TableOptionError):
+    """Exception raised when no header, body or footer is provided
+
+    This class is a subclass of :class:`TableOptionError`.
+    """
+
+    def __init__(self):
+        super().__init__(self._message())
+
+    def _message(self) -> str:
+        return "At least one of header, body or footer must be provided."
+
+
 class InvalidCellPaddingError(TableOptionError):
     """Exception raised when the cell padding is invalid
 

tests/test_convert.py

@@ -1,7 +1,11 @@
 import pytest
 
 from table2ascii import table2ascii as t2a
-from table2ascii.exceptions import BodyColumnCountMismatchError, FooterColumnCountMismatchError
+from table2ascii.exceptions import (
+    BodyColumnCountMismatchError,
+    FooterColumnCountMismatchError,
+    NoHeaderBodyOrFooterError,
+)
 
 
 def test_header_body_footer():
@@ -117,6 +121,11 @@ def test_footer():
     assert text == expected
 
 
+def test_no_header_body_or_footer():
+    with pytest.raises(NoHeaderBodyOrFooterError):
+        t2a()
+
+
 def test_header_footer_unequal():
     with pytest.raises(FooterColumnCountMismatchError):
         t2a(