Revert requestTermination change

[erikcorry]

A better solution was found in the form of https://chromium-review.googlesource.com/c/v8/v8/+/7734848 and so this interface is unused.

[ask-bonk]

I'm Bonk, and I've done a quick review of your PR.

This PR reverts the requestTermination / isTerminationRequested mechanism from the C++ JSG layer, but the Rust FFI layer still depends on those removed methods.

Issues (by severity)

1. Build break (high): The Rust FFI layer in src/rust/jsg/ has active callers of the removed IsolateBase::requestTermination() and IsolateBase::isTerminationRequested() methods. These files need corresponding changes:

   • src/rust/jsg/ffi.c++:1089-1095 — isolate_request_termination() and isolate_is_termination_requested() call the removed methods
   • src/rust/jsg/ffi.h:343-344 — declares those FFI functions
   • src/rust/jsg/v8.rs:555-556 — Rust-side FFI declarations
   • src/rust/jsg/lib.rs:599-623 — Lock::request_termination() and Lock::is_termination_requested() public methods
   • src/rust/jsg/lib.rs:819 — catch_panic() calls lock.request_termination() after converting a Rust panic to a JS exception
   • src/rust/jsg-test/tests/resource_callback.rs:441-488 — test that asserts on is_termination_requested()

   The catch_panic case is particularly important: it's the Rust panic handler that terminates the isolate after a panic to prevent GC from observing partially-mutated state. This needs a replacement — likely switching to terminateExecution() (which is still available on IsolateBase) instead of the removed requestTermination(). The is_termination_requested() check in the test would need a different assertion strategy since there's no longer a flag to query.

[ask-bonk]

The C++ side is fine, but the Rust FFI layer still calls requestTermination() and isTerminationRequested() which no longer exist:

• src/rust/jsg/ffi.c++:1089-1095 — will fail to compile
• src/rust/jsg/lib.rs:819 — catch_panic() calls lock.request_termination() to terminate the isolate after a Rust panic, preventing GC from observing partially-mutated state. This is an important safety mechanism that needs a replacement (probably terminateExecution()).
• src/rust/jsg-test/tests/resource_callback.rs — test asserts on is_termination_requested()

These all need to be updated as part of this revert.

[ask-bonk]

Review posted successfully on PR #6626. Here's a summary:

High-severity issue found: The PR removes requestTermination() and isTerminationRequested() from the C++ IsolateBase and Lock classes, but the Rust FFI layer in src/rust/jsg/ still actively calls both methods across 6 files:

• FFI bridge (ffi.c++, ffi.h, v8.rs) — will fail to compile
• Lock wrapper (lib.rs) — exposes request_termination() and is_termination_requested() to Rust code
• Panic handler (lib.rs:819) — catch_panic() calls request_termination() to safely terminate the isolate after a Rust panic, preventing GC from observing partially-mutated state. This is a safety-critical path that needs a replacement.
• Test (resource_callback.rs) — asserts on is_termination_requested()

github run

[github-actions]

The generated output of @cloudflare/workers-types matches the snapshot in types/generated-snapshot 🎉