Discarding origin is brittle

[fcollonval]

I find the cleaning of the origin too brittle:

pycrdt/python/pycrdt/_transaction.py

Line 80 in 181c192

del self._doc._origins[origin_hash]

Reasons:

• You cannot be sure the transaction will be discarded at exit.
• The hashed_origin obtained is not the one stored in the __init__, how could you be sure you are not removing a reference to another hash?
• The resource clearing is not happening in the mirror action of its creation; aka init <=> del

[davidbrochart]

• The hashed_origin obtained is not the one stored in the __init__, how could you be sure you are not removing a reference to another hash?

You mean the hashed origin obtained in __exit__? If so, yes it is the one stored in __enter__, previously computed and registered in __init__. Am I missing something?

• The resource clearing is not happening in the mirror action of its creation; aka init <=> del

A transaction should only be used with a context manager, so registering an origin in __init__ is equivalent to registering it in __enter__, which is symmetrical to the clearing happening in __exit__.
But I agree that users could create the Transaction object and never use it in a context manager, for whatever reason. Moving the registering to __enter__ should handle that case, right? I guess that's also what you meant by:

• You cannot be sure the transaction will be discarded at exit.

[fcollonval]

In adding the transaction to event - I needed to revisit that part. See #233 for a proposal.