can't recover deleted document

[maxlath]

Description

While upgrading from CouchDB 1.7.x to 3.1.x (installed via Docker), I noticed this change in behavior: what works to recover a deleted document on 1.7.x seems to fail on 3.1.x

Steps to Reproduce

# create db
curl -XPUT "http://localhost:5984/some-db"
# put a doc
rev1=$(curl -XPUT "http://localhost:5984/some-db/foo" -d '{"bar":123}' | jq '.rev' -r)
# delete doc
rev2=$(curl -XDELETE "http://localhost:5984/some-db/foo?rev=${rev1}" | jq '.rev' -r)
# try to undelete: fails, {"error":"conflict","reason":"Document update conflict."}
curl -XPUT "http://localhost:5984/some-db/foo?rev=${rev2}" -d '{"bar":123}' | jq '.rev' -r

Expected Behaviour

Recover the document, as in previous versions

Your Environment

Docker image: couchdb:3.1

{"couchdb":"Welcome","version":"3.1.0","git_sha":"ff0feea20","uuid":"f8d9db8433165a5f14a63035b0a8ef08","features":["access-ready","partitioned","pluggable-storage-engines","reshard","scheduler"],"vendor":{"name":"The Apache Software Foundation"}}

[wohali]

You do not need to specify the deleted rev if you are re-creating a previously deleted document. This example works:

curl -XPUT "http://localhost:5984/some-db"
rev1=$(curl -XPUT "http://localhost:5984/some-db/foo" -d '{"bar":123}' | jq '.rev' -r)
rev2=$(curl -XDELETE "http://localhost:5984/some-db/foo?rev=${rev1}" | jq '.rev' -r)
curl -XPUT "http://localhost:5984/some-db/foo" -d '{"bar":123}' | jq '.rev' -r

This adheres to the principle of least surprise -- you shouldn't have to have prior knowledge about the tombstone (deleted document)'s _rev value just to re-create the document.