flattening a lot of fired Deferreds causes a RecursionError

[twisted-trac]

	@pwestlak-xilinx reported
Trac ID	trac#10125
Type	defect
Created	2021-03-11 12:11:12Z

This gives a recursion error after printing 197 lines:

import sys
from twisted.internet import reactor, defer, task
from twisted.web.template import flatten

def output(stuff):
    sys.stdout.write(stuff.decode())

def sync(reactor):
    return flatten(None, [defer.succeed(str(i)+'\n') for i in range(1000)], output)

task.react(sync)

Searchable metadata

trac-id__10125 10125
type__defect defect
reporter__pwestlak_xilinx pwestlak-xilinx
priority__high high
milestone__None None
branch__ 
branch_author__ 
status__closed closed
resolution__fixed fixed
component__web web
keywords__None None
time__1615464672713574 1615464672713574
changetime__1617444162694748 1617444162694748
version__None None
owner__glyph glyph

[twisted-trac]

	@glyph commented

In review at https://github.com/twisted/twisted/pull/1549/files

[twisted-trac]

	@wsanchez set owner to @glyph

Looks good

[twisted-trac]

	@glyph set status to closed

In changeset 12d53db

#!CommitTicketReference repository="" revision="12d53dbd106e424425137c29ab3b9cf2a5e2bf34"
Merge pull request #1549 from twisted/10125-template-recursion-error

Author: glyph

Reviewer: wsanchez,pwestlak-xilinx

Fixes: ticket:10125

Fix and simplify trampoline for twisted.web.template flattening to avoid RecursionErrors with synchronous deferreds.