From 28c8c155ce8557e8eda5908a45072cbe817c7701 Mon Sep 17 00:00:00 2001
From: Simon Damberg <49840909+SimonDamberg@users.noreply.github.com>
Date: Sun, 21 Nov 2021 13:36:22 +0100
Subject: [PATCH] Improve Subscription of TelegramObject (#2719)

Co-authored-by: Hinrich Mahler <22366557+Bibo-Joshi@users.noreply.github.com>
Co-authored-by: Harshil <37377066+harshil21@users.noreply.github.com>
---
 telegram/_message.py         |  5 +----
 telegram/_telegramobject.py  | 21 +++++++++++++++++++--
 tests/test_message.py        |  5 -----
 tests/test_telegramobject.py | 16 +++++++++++++++-
 4 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/telegram/_message.py b/telegram/_message.py
index 5ec6cc9b1..ea6ac02b1 100644
--- a/telegram/_message.py
+++ b/telegram/_message.py
@@ -672,16 +672,13 @@ class Message(TelegramObject):
 
         for attachment_type in MessageAttachmentType:
             if self[attachment_type]:
-                self._effective_attachment = self[attachment_type]
+                self._effective_attachment = self[attachment_type]  # type: ignore[assignment]
                 break
         else:
             self._effective_attachment = None
 
         return self._effective_attachment  # type: ignore[return-value]
 
-    def __getitem__(self, item: str) -> Any:  # pylint: disable=inconsistent-return-statements
-        return self.chat.id if item == 'chat_id' else super().__getitem__(item)
-
     def to_dict(self) -> JSONDict:
         """See :meth:`telegram.TelegramObject.to_dict`."""
         data = super().to_dict()
diff --git a/telegram/_telegramobject.py b/telegram/_telegramobject.py
index 61928b825..46934f0fc 100644
--- a/telegram/_telegramobject.py
+++ b/telegram/_telegramobject.py
@@ -34,7 +34,16 @@ TO = TypeVar('TO', bound='TelegramObject', covariant=True)
 
 
 class TelegramObject:
-    """Base class for most Telegram objects."""
+    """Base class for most Telegram objects.
+
+    Objects of this type are subscriptable with strings, where ``telegram_object[attribute_name]``
+    is equivalent to ``telegram_object.attribute_name``. If the object does not have an attribute
+    with the appropriate name, a :exc:`KeyError` will be raised.
+
+    .. versionchanged:: 14.0
+        ``telegram_object['from']`` will look up the key ``from_user``. This is to account for
+        special cases like :attr:`Message.from_user` that deviate from the official Bot API.
+    """
 
     # type hints in __new__ are not read by mypy (https://github.com/python/mypy/issues/1021). As a
     # workaround we can type hint instance variables in __new__ using a syntax defined in PEP 526 -
@@ -62,7 +71,15 @@ class TelegramObject:
         return str(self.to_dict())
 
     def __getitem__(self, item: str) -> object:
-        return getattr(self, item, None)
+        if item == 'from':
+            item = 'from_user'
+        try:
+            return getattr(self, item)
+        except AttributeError as exc:
+            raise KeyError(
+                f"Objects of type {self.__class__.__name__} don't have an attribute called "
+                f"`{item}`."
+            ) from exc
 
     @staticmethod
     def _parse_data(data: Optional[JSONDict]) -> Optional[JSONDict]:
diff --git a/tests/test_message.py b/tests/test_message.py
index 08517b364..9583bbdbd 100644
--- a/tests/test_message.py
+++ b/tests/test_message.py
@@ -321,11 +321,6 @@ class TestMessage:
 
         assert new.to_dict() == message_params.to_dict()
 
-    def test_dict_approach(self, message):
-        assert message['text'] == message.text
-        assert message['chat_id'] == message.chat_id
-        assert message['no_key'] is None
-
     def test_parse_entity(self):
         text = (
             b'\\U0001f469\\u200d\\U0001f469\\u200d\\U0001f467'
diff --git a/tests/test_telegramobject.py b/tests/test_telegramobject.py
index 39f7073b8..0d0df8acb 100644
--- a/tests/test_telegramobject.py
+++ b/tests/test_telegramobject.py
@@ -26,7 +26,7 @@ try:
 except ImportError:
     ujson = None
 
-from telegram import TelegramObject
+from telegram import TelegramObject, Message, Chat, User
 
 
 class TestTelegramObject:
@@ -131,3 +131,17 @@ class TestTelegramObject:
         elif bot_inst is None:
             with pytest.raises(RuntimeError):
                 tg_object.get_bot()
+
+    def test_subscription(self):
+        # We test with Message because that gives us everything we want to test - easier than
+        # implementing a custom subclass just for this test
+        chat = Chat(2, Chat.PRIVATE)
+        user = User(3, 'first_name', False)
+        message = Message(1, None, chat=chat, from_user=user, text='foobar')
+        assert message['text'] == 'foobar'
+        assert message['chat'] is chat
+        assert message['chat_id'] == 2
+        assert message['from'] is user
+        assert message['from_user'] is user
+        with pytest.raises(KeyError, match="Message don't have an attribute called `no_key`"):
+            message['no_key']