Fix crash when no commands are available

fimfarchive/commands/root.py

@@ -93,6 +93,9 @@ class RootCommand(Command):
             'Fimfarchive, ensuring that history is preseved.\n\n',
         ]
 
+        if not self.commands:
+            return ''.join(text).strip()
+
         commands = sorted(cmd for cmd in self.commands.keys())
         adjust = max(len(cmd) for cmd in commands) + 2
 

tests/commands/test_root.py

@@ -108,6 +108,13 @@ class TestRootCommanad():
         assert "failure  Command that returns 1." in doc
         assert "truncated documentation line" not in doc
 
+    def test_root_usage_without_commands(self, root):
+        """
+        Tests usage contains text when no commands are available.
+        """
+        type(root).commands = dict()
+        assert root.usage.strip()
+
     def test_root_call_without_args(self, root, success, failure):
         """
         Tests `SystemExit` is raised if called without arguments.