Fix HelpFormatter.write_usage with no args

CHANGES.rst

@@ -1,5 +1,16 @@
 .. currentmodule:: click
 
+Version 8.3.4
+-------------
+
+Unreleased
+
+-   Fix :meth:`HelpFormatter.write_usage` to write the usage prefix when called
+    with no ``args``. Previously, an empty string was passed through
+    :func:`wrap_text`, which dropped the ``initial_indent`` and produced a
+    blank line. :issue:`3360`
+
+
 Version 8.3.3
 -------------
 

src/click/formatting.py

@@ -158,6 +158,13 @@ def write_usage(self, prog: str, args: str = "", prefix: str | None = None) -> N
         usage_prefix = f"{prefix:>{self.current_indent}}{prog} "
         text_width = self.width - self.current_indent
 
+        if not args:
+            # Without args, ``wrap_text`` would drop the ``initial_indent``
+            # because the text is empty, so write the prefix directly.
+            self.write(usage_prefix.rstrip())
+            self.write("\n")
+            return
+
         if text_width >= (term_len(usage_prefix) + 20):
             # The arguments will fit to the right of the prefix.
             indent = " " * term_len(usage_prefix)

tests/test_formatting.py

@@ -366,3 +366,22 @@ def test_help_formatter_write_text():
     actual = formatter.getvalue()
     expected = "  Lorem ipsum dolor sit amet,\n  consectetur adipiscing elit\n"
     assert actual == expected
+
+
+def test_help_formatter_write_usage_no_args():
+    formatter = click.HelpFormatter()
+    formatter.write_usage("program")
+    assert formatter.getvalue() == "Usage: program\n"
+
+
+def test_help_formatter_write_usage_no_args_custom_prefix():
+    formatter = click.HelpFormatter()
+    formatter.write_usage("program", prefix="Try: ")
+    assert formatter.getvalue() == "Try: program\n"
+
+
+def test_help_formatter_write_usage_no_args_indented():
+    formatter = click.HelpFormatter()
+    formatter.current_indent = 10
+    formatter.write_usage("program")
+    assert formatter.getvalue() == "   Usage: program\n"