ive just read the source code for chain() and it's a bit of a disaster. because if i do this:
w = writer1.chain(writer2).chain(writer3)
writer2 is lost. it's doing the chaining wrong. my high school comp sci teacher would be unimpressed
it works for your use case right now because it only handles exactly two writers. but if we fix it to correctly implement chaining then it would not work for your case in the general sense.
we can fix both issues at once by 1. fixing the chaining so that if self._chain is non-None we traverse the list through to the end for the linked list append, and 2. looking at the type of object sent and if it's just a callable, wrapping it in a helper object CallableRewriter that uses that callable and also supports the rest of the Rewriter protocol including self._chain.
ive just read the source code for chain() and it's a bit of a disaster. because if i do this:
writer2 is lost. it's doing the chaining wrong. my high school comp sci teacher would be unimpressed
it works for your use case right now because it only handles exactly two writers. but if we fix it to correctly implement chaining then it would not work for your case in the general sense.
we can fix both issues at once by 1. fixing the chaining so that if
self._chain
is non-None we traverse the list through to the end for the linked list append, and 2. looking at the type of object sent and if it's just a callable, wrapping it in a helper objectCallableRewriter
that uses that callable and also supports the rest of theRewriter
protocol includingself._chain
.Originally posted by @zzzeek in https://github.com/sqlalchemy/alembic/discussions/1332#discussioncomment-7369839