[DISCUSS] Creating new deleted documents in CouchDB 4

[Nick Vatamaniuc]

Hi everyone,

While running PouchDB replication unit tests against the CouchDB 4
replicator PR branch (thanks to Garren Smith, who helped set up the
tests), we had noticed a doc update API incompatibility between
CouchDB 3.x/PouchDB and the prototype/fdb-layer branch: CouchDB
3.x/PouchDB allow creating new deleted documents and
prototype/fdb-layer branch doesn't.

For example:

$ http put $DB1/mydb/doc1 _deleted:='true' a=b
HTTP/1.1 200 OK

{
    "id": "doc1",
    "ok": true,
    "rev": "1-ad7eb689fcae75e7a7edb57dc1f30939"
}

$ http $DB1/mydb/doc1?deleted=true
HTTP/1.1 200 OK

{
    "_deleted": true,
    "_id": "doc1",
    "_rev": "1-ad7eb689fcae75e7a7edb57dc1f30939",
    "a": "b"
}

On prototype/fdb-layer it returns a 409 conflict error

I opened a PR to make the prototype/fdb-layer branch behave the same
and keep the API compatibility, but also wanted to see what the
community thinks.

https://github.com/apache/couchdb/pull/3123

Would we want to keep compatibility with CouchDB 3.x/PouchDB or,
return a conflict (409), like the prototype/fdb-layer branch does?

My vote is for compatibility.

Thanks,
-Nick