parentTerminal doesn't always work

[drrnkin]

Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: Version: 1.86.1 (system setup) Commit: 31c37ee8f63491495ac49e43b8544550fbae4533 Date: 2024-02-07T09:08:20.941Z Electron: 27.2.3 ElectronBuildId: 26495564 Chromium: 118.0.5993.159 Node.js: 18.17.1 V8: 11.8.172.18-electron.0 OS: Windows_NT x64 10.0.19045
• OS Version: Edition Windows 10 Enterprise Version 22H2 Installed on ‎1/‎15/‎2021 OS build 19045.3930 Experience Windows Feature Experience Pack 1000.19053.1000.0

Steps to Reproduce:

This is precisely the same as #131594. The OP-provided code opens terminals that are separate from each other (not split). Ditto for the very similar code quoted in response (the last block). Unfortunately the OP did not follow up but I'm seeing exactly the same issue.

I've definitely seen parentTerminal work when creating two terminals at the same moment and making one the parentTerminal of the other. The option seems to be ignored if the supplied terminal was not created at the same moment, i.e. stored and used in a subsequent call.

[apeters-brex]

For me, the example from https://github.com/microsoft/vscode/issues/131594 works, but fails when I try to split from an existing terminal (one not created within that same function).

For instance, if you take that same snippet and change options_1 to include

location: { parentTerminal: vscode.window.terminals[0] },

Then run the command when you have an existing terminal, terminal_1 does not get split from that existing terminal.