Fix shortest-only completion at an empty root prompt

click_repl/_completer.py

@@ -234,7 +234,7 @@ def _get_completion_for_cmd_args(
                     self.shortest_only
                     and not incomplete  # just typed a space
                     # not selecting a value for a longer version of this option
-                    and args[-1] not in opts
+                    and (not args or args[-1] not in opts)
                 ):
                     opts = [min(opts, key=len)]
 

tests/test_completion/test_common_tests/test_option_completion.py

@@ -133,3 +133,19 @@ def shortest_only(foo, bar, foobar):
 
     completions = list(c.get_completions(Document("shortest-only ")))
     assert {x.text for x in completions} == {"-f", "--foo", "-b", "--bar", "--foobar"}
+
+
+def test_shortest_only_at_empty_root_prompt(capsys):
+    @click.group()
+    @click.option("--verbose", "-v", is_flag=True)
+    def root(verbose):
+        pass
+
+    @root.command()
+    def child():
+        pass
+
+    completer = ClickCompleter(root, click.Context(root), shortest_only=True)
+    completions = list(completer.get_completions(Document("")))
+    assert {item.text for item in completions} == {"-v", "child"}
+    assert capsys.readouterr().out == ""