bots: Find external packaged bots via 'zulip_bots.registry' entry_point.

Added dependency upon supporting small 'entrypoints' package.

Add test case.

Author: neiljp

zulip_bots/setup.py

@@ -66,6 +66,7 @@
         "lxml",
         "BeautifulSoup4",
         "typing_extensions",
+        "entrypoints",
     ],
 )
 

zulip_bots/zulip_bots/finder.py

@@ -5,6 +5,8 @@
 from pathlib import Path
 from typing import Any, Optional, Tuple
 
+import entrypoints
+
 current_dir = os.path.dirname(os.path.abspath(__file__))
 
 
@@ -25,6 +27,23 @@ def import_module_by_name(name: str) -> Any:
         return None
 
 
+class DuplicateRegisteredBotName(Exception):
+    pass
+
+
+def import_module_from_zulip_bot_registry(name: str) -> Any:
+    registered_bots = entrypoints.get_group_all("zulip_bots.registry")
+    matching_bots = [bot for bot in registered_bots if bot.name == name]
+
+    if len(matching_bots) == 1:  # Unique matching entrypoint
+        return matching_bots[0].load()
+
+    if len(matching_bots) > 1:
+        raise DuplicateRegisteredBotName(name)
+
+    return None  # no matches in registry
+
+
 def resolve_bot_path(name: str) -> Optional[Tuple[Path, str]]:
     if os.path.isfile(name):
         bot_path = Path(name)

zulip_bots/zulip_bots/run.py

@@ -139,6 +139,16 @@ def main() -> None:
             if args.provision:
                 print("ERROR: Could not load bot's module for '{}'. Exiting now.")
                 sys.exit(1)
+        else:
+            try:
+                lib_module = finder.import_module_from_zulip_bot_registry(args.bot)
+            except finder.DuplicateRegisteredBotName:
+                print(
+                    "ERROR: Found duplicate entries for bot name in zulip bot registry. Exiting now."
+                )
+                sys.exit(1)
+            if lib_module:
+                bot_name = args.bot
 
     if lib_module is None:
         print("ERROR: Could not load bot module. Exiting now.")

zulip_bots/zulip_bots/tests/test_run.py

@@ -7,6 +7,8 @@
 from unittest import TestCase, mock
 from unittest.mock import patch
 
+import entrypoints
+
 import zulip_bots.run
 from zulip_bots.lib import extract_query_without_mention
 
@@ -15,6 +17,7 @@ class TestDefaultArguments(TestCase):
 
     our_dir = os.path.dirname(__file__)
     path_to_bot = os.path.abspath(os.path.join(our_dir, "../bots/giphy/giphy.py"))
+    packaged_bot_entrypoint = entrypoints.EntryPoint("packaged_bot", "module_name", None)
 
     @patch("sys.argv", ["zulip-run-bot", "giphy", "--config-file", "/foo/bar/baz.conf"])
     @patch("zulip_bots.run.run_message_handler_for_bot")
@@ -48,6 +51,27 @@ def test_argument_parsing_with_bot_path(
             quiet=False,
         )
 
+    @patch("sys.argv", ["zulip-run-bot", "packaged_bot", "--config-file", "/foo/bar/baz.conf"])
+    @patch("zulip_bots.run.run_message_handler_for_bot")
+    def test_argument_parsing_with_zulip_bot_registry(
+        self, mock_run_message_handler_for_bot: mock.Mock
+    ) -> None:
+        with patch("zulip_bots.run.exit_gracefully_if_zulip_config_is_missing"):
+            with patch("zulip_bots.finder.entrypoints.EntryPoint.load"):
+                with patch(
+                    "zulip_bots.finder.entrypoints.get_group_all",
+                    return_value=[self.packaged_bot_entrypoint],
+                ):
+                    zulip_bots.run.main()
+
+        mock_run_message_handler_for_bot.assert_called_with(
+            bot_name="packaged_bot",
+            config_file="/foo/bar/baz.conf",
+            bot_config_file=None,
+            lib_module=mock.ANY,
+            quiet=False,
+        )
+
     def test_adding_bot_parent_dir_to_sys_path_when_bot_name_specified(self) -> None:
         bot_name = "helloworld"  # existing bot's name
         expected_bot_dir_path = Path(