Fix deprecated label formatting

CHANGES.rst

@@ -9,6 +9,8 @@ Unreleased
     tabs in option help text are now escaped, keeping the original completion
     format while still supporting multi-line help. :issue:`3502`
     :issue:`3043` :pr:`3504` :pr:`3508`
+-   Deprecated commands and options with empty or missing help text no longer
+    render a stray leading space before the ``(DEPRECATED)`` label. :pr:`3509`
 
 
 Version 8.4.1

src/click/core.py

@@ -1189,7 +1189,8 @@ def format_help_text(self, ctx: Context, formatter: HelpFormatter) -> None:
             text = ""
 
         if self.deprecated:
-            text = f"{_(text)} {_format_deprecated_label(self.deprecated)}"
+            label = _format_deprecated_label(self.deprecated)
+            text = f"{_(text)} {label}" if text else label
 
         if text:
             formatter.write_paragraph()
@@ -2826,7 +2827,7 @@ def __init__(
 
         if deprecated:
             label = _format_deprecated_label(deprecated)
-            help = f"{help} {label}" if help is not None else label
+            help = f"{help} {label}" if help else label
 
         self.prompt = prompt_text
         self.confirmation_prompt = confirmation_prompt

tests/test_commands.py

@@ -491,6 +491,22 @@ def cli():
         assert deprecated in result.output
 
 
+@pytest.mark.parametrize("deprecated", [True, "USE OTHER COMMAND INSTEAD"])
+@pytest.mark.parametrize("doc", ["", None])
+def test_deprecated_empty_help_no_leading_space(runner, doc, deprecated):
+    """A command with empty or missing help text must render the deprecation
+    label at the normal indentation, without a stray leading space.
+    """
+
+    @click.command(deprecated=deprecated, help=doc)
+    def cli():
+        pass
+
+    out = runner.invoke(cli, ["--help"]).output
+    assert "\n  (DEPRECATED" in out
+    assert "\n   (DEPRECATED" not in out
+
+
 @pytest.mark.parametrize("deprecated", [True, "USE OTHER COMMAND INSTEAD"])
 def test_deprecated_in_invocation(runner, deprecated):
     @click.command(deprecated=deprecated)

tests/test_options.py

@@ -58,6 +58,20 @@ def cmd(foo):
         assert deprecated in result.output
 
 
+@pytest.mark.parametrize(
+    ("deprecated", "expected"),
+    [(True, "(DEPRECATED)"), ("USE B INSTEAD", "(DEPRECATED: USE B INSTEAD)")],
+)
+@pytest.mark.parametrize("help_text", ["", None])
+def test_deprecated_empty_help_no_leading_space(help_text, deprecated, expected):
+    """An option with empty or missing help text must not gain a stray leading
+    space before the deprecation label.
+    """
+    opt = click.Option(["--foo"], help=help_text, deprecated=deprecated)
+    ctx = click.Context(click.Command("cli"))
+    assert opt.get_help_record(ctx)[1] == expected
+
+
 @pytest.mark.parametrize("deprecated", [True, "USE B INSTEAD"])
 def test_deprecated_warning(runner, deprecated):
     @click.command()