fix: Don't render anything when code block output is empty

By empty, we mean absolutely empty. A single blank character will be (converted and) rendered.

Issue-17: #17

src/markdown_exec/formatters/base.py

@@ -105,6 +105,9 @@ def base_format(
         logger.warning(log_message)
         return markdown.convert(str(error))
 
+    if not output:
+        return Markup()
+
     if html:
         if source:
             placeholder = str(uuid4())

tests/test_base_formatter.py

@@ -58,3 +58,18 @@ def test_render_console_plus_ansi_result(md: Markdown) -> None:
         result="ansi",
     )
     assert "<code>ansi" in markup
+
+
+def test_dont_render_anything_if_output_is_empty(md: Markdown) -> None:
+    """Assert nothing is rendered if output is empty.
+
+    Parameters:
+        md: A Markdown instance (fixture).
+    """
+    markup = base_format(
+        language="bash",
+        run=lambda code, **_: "",
+        code="whatever",
+        md=md,
+    )
+    assert not markup