Bug 312797 – [Swift Testing] Add Swift-callable wrapper around InstanceMethodSwizzler for TestWebKitAPI

• Status: RESOLVED
• Resolution: FIXED
• Component: Tools / Tests

[zak ridouh]

The C++ InstanceMethodSwizzler RAII helper is gated behind #ifdef
__cplusplus and is not callable from Swift, so Swift tests in
TestWebKitAPI cannot mock Objective-C runtime behavior. This is the
first piece of infrastructure needed to port AppKit-heavy tests
(NSMenu pop-ups, gesture recognizers, drag-and-drop) to the new
Swift Testing framework.

Add TestMethodSwizzler, a thin @interface around InstanceMethodSwizzler
that takes a block, runs it through imp_implementationWithBlock, and
restores the original implementation in -dealloc. Swift callers hold
the swizzler in a local binding for as long as the swizzle should
remain in effect, mirroring the C++ RAII pattern.

Add a smoke test that swizzles a no-arg Int-returning method on a
Swift @objc class, verifies the replacement IMP is called, and
verifies the original is restored once the swizzler is dropped.

[Radar WebKit Bug Importer]

<rdar://problem/175186623>

[zak ridouh]

Pull request: https://github.com/WebKit/WebKit/pull/63141

[EWS]

Committed 312863@main (a41a909424f0): <https://commits.webkit.org/312863@main>

Reviewed commits have been landed. Closing PR #63141 and removing active labels.