Cannot edit caption of File uploaded by other User in Channel

[NotStatilko]

Code that causes the issue

1. Make a Channel (C) from user A
2. Add user B to C & grant all Admin privileges
3. Upload any Document to C from B
4. Run code example below from user A

from telethon.sync import TelegramClient
from telethon.types import PeerChannel

API_ID = ...
API_HASH = ...
CHANNEL = PeerChannel(...)

client = TelegramClient(...)
client.start()

channel = client.get_entity(CHANNEL)

message = next(client.iter_messages(channel))
print(message.edit('Test caption') is None)
# ^ Message is NOT edited if result is True

Expected behavior

I believe that user A (with Owner privileges) should change caption of Message of user B.

Actual behavior

Document message is NOT edited (None returned).

Traceback

No Traceback.

Telethon version

1.29.3 (HEAD)

Python version

3.9.2

Operating system (including distribution name and version)

Debian 11

Other details

This can be easily done within Telegram. Moreover, if B edit caption of file uploaded by himself, then things is OK (Document caption is edited).

Checklist

• The error is in the library's code, and not in my own.
• I have searched for this issue before posting it and there isn't an open duplicate.
• I ran pip install -U https://github.com/LonamiWebs/Telethon/archive/v1.zip and triggered the bug in the latest version.

[NotStatilko]

Little debug show me that probably the problem in this two lines of code:

        if self.fwd_from or not self.out or not self._client:
            return None  # We assume self.out was patched for our chat

As far i understand, self.out stands for "We are sender of this Message or not?". What is a reason behind using this in such statement? What if we just remove the or not self.out? This will resolve the problem described in this issue.

UPD: It seems that client.edit_message works fine on this Issue.

[Lonami]

Thanks for the very detailed report. To be fair, it's probably safe to remove that check entirely.

Trying to emulate server rules locally does not often end well.