Chem.ReplaceCore(labelByIndex = True): Issue with 0-indexed atoms

[ZCCheng97]

Describe the bug Using Chem.ReplaceCore() to obtain fragments with the attachment points labelled by the index of the core. However, while indices of fragments are labelled correctly for eg. [1*]CC if it was originally attached to the 1-index atom on the core, it returns *CC instead of [0*]CC if the fragment was attached originally to the 0-index core atom.

To Reproduce

backboneS = "OCCCCO"
queryS = "COCCCCOC(C)(C)"

query = Chem.MolFromSmiles(queryS)
backbone = Chem.MolFromSmiles(backboneS)

tmp = Chem.ReplaceCore(query,backbone,labelByIndex=True)
rs = Chem.GetMolFrags(tmp,asMols=True)

for frag in rs:
    print(Chem.MolToSmiles(frag))

The output ended up as

*C
[5*]C(C)C

Expected behavior What I had expected from the output.

[0*]C
[5*]C(C)C

Configuration (please complete the following information):

• RDKit version: 2024.03.2
• Python version: 3.12.3
• Are you using conda? Yes