Java — Support Post‑Emit Execution Step in Java Emitter

[lirenhe]

Problem Statement

During SDK generation, there are cases where Java SDKs require post‑generation fixes or adjustments that cannot be cleanly handled inside the TypeSpec emitter logic today. Currently, Java lacks a standard post‑emit hook, which forces teams to rely on ad‑hoc pipeline steps or manual follow‑ups.

We also got the ask from Foundry team that Python SDK generation requires post‑generation scripts to update the generated code.
e.g. update code emitter outputs and to deal with emitted code issues that service team hasn't decided the correct approach for yet.

Proposal

Add post‑emit execution support in the Java emitter
The emitter should invoke a script after code emission but before downstream pipeline steps

[srnagar]

@lirenhe "there are cases where Java SDKs require post‑generation fixes or adjustments that cannot be cleanly handled inside the TypeSpec emitter logic today"

Java already supports Java customization as the final step to customize the generated code. Could you please elaborate on what scenarios require post-emit hooks that cannot be handled inside the emitter?

[lirenhe]

@srnagar, I added some context of service's ask in the epic and you could also check Azure/azure-sdk-tools#10366 for the previous discussion.