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

Added dependency upon supporting small 'entrypoints' package.

Add test case.

zulip_bots/zulip_bots/finder.py

@@ -1,6 +1,7 @@
 import importlib
 import importlib.abc
 import importlib.util
+import importlib.metadata
 import os
 from pathlib import Path
 from typing import Any, Optional, Tuple
@@ -25,6 +26,23 @@ 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 = importlib.metadata.entry_points()["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

@@ -48,6 +48,13 @@ def parse_args() -> argparse.Namespace:
         help="try running the bot even if dependencies install fails",
     )
 
+    parser.add_argument(
+        "--registry",
+        "-r",
+        action="store_true",
+        help="run the bot via zulipt_bot registry",
+    )
+
     parser.add_argument("--provision", action="store_true", help="install dependencies for the bot")
 
     args = parser.parse_args()
@@ -109,36 +116,45 @@ def exit_gracefully_if_bot_config_file_does_not_exist(bot_config_file: Optional[
 def main() -> None:
     args = parse_args()
 
-    result = finder.resolve_bot_path(args.bot)
-    if result:
-        bot_path, bot_name = result
-        sys.path.insert(0, os.path.dirname(bot_path))
-
-        if args.provision:
-            provision_bot(os.path.dirname(bot_path), args.force)
-
+    if args.registry:
         try:
-            lib_module = finder.import_module_from_source(bot_path.as_posix(), bot_name)
-        except ImportError:
-            req_path = os.path.join(os.path.dirname(bot_path), "requirements.txt")
-            with open(req_path) as fp:
-                deps_list = fp.read()
-
-            dep_err_msg = (
-                "ERROR: The following dependencies for the {bot_name} bot are not installed:\n\n"
-                "{deps_list}\n"
-                "If you'd like us to install these dependencies, run:\n"
-                "    zulip-run-bot {bot_name} --provision"
-            )
-            print(dep_err_msg.format(bot_name=bot_name, deps_list=deps_list))
+            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)
-    else:
-        lib_module = finder.import_module_by_name(args.bot)
         if lib_module:
-            bot_name = lib_module.__name__
+            bot_name = args.bot
+    else:
+        result = finder.resolve_bot_path(args.bot)
+        if result:
+            bot_path, bot_name = result
+            sys.path.insert(0, os.path.dirname(bot_path))
+
             if args.provision:
-                print("ERROR: Could not load bot's module for '{}'. Exiting now.")
+                provision_bot(os.path.dirname(bot_path), args.force)
+
+            try:
+                lib_module = finder.import_module_from_source(bot_path.as_posix(), bot_name)
+            except ImportError:
+                req_path = os.path.join(os.path.dirname(bot_path), "requirements.txt")
+                with open(req_path) as fp:
+                    deps_list = fp.read()
+
+                dep_err_msg = (
+                    "ERROR: The following dependencies for the {bot_name} bot are not installed:\n\n"
+                    "{deps_list}\n"
+                    "If you'd like us to install these dependencies, run:\n"
+                    "    zulip-run-bot {bot_name} --provision"
+                )
+                print(dep_err_msg.format(bot_name=bot_name, deps_list=deps_list))
                 sys.exit(1)
+        else:
+            lib_module = finder.import_module_by_name(args.bot)
+            if lib_module:
+                bot_name = lib_module.__name__
+                if args.provision:
+                    print("ERROR: Could not load bot's module for '{}'. Exiting now.")
+                    sys.exit(1)
 
     if lib_module is None:
         print("ERROR: Could not load bot module. Exiting now.")

zulip_bots/zulip_bots/tests/test_run.py

@@ -1,7 +1,9 @@
 #!/usr/bin/env python3
+import importlib
 import os
 import sys
 import unittest
+from importlib.metadata import EntryPoint
 from pathlib import Path
 from typing import Optional
 from unittest import TestCase, mock
@@ -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 = 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.importlib.metadata.EntryPoint.load"):
+                with patch(
+                    "zulip_bots.finder.importlib.metadata.entry_points",
+                    return_value={"zulip_bots.registry": [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(