Dynamic Invocation

[steipete]

With using objc_msgForward, we can add hooks without offering a type signature.

_ = try testObj.hook(#selector(TestClass.executeBlock)) { bSelf in
  print("Before Interposing Dynamic Hook for \(bSelf)")
}

This is slightly slower than the typed call, but way more convenient

This is achieved with a few tricks:

1. We install the subclass
2. The hooked method gets a super trampoline
3. we add a interpose_origMethod and copy the implementation (which is the super trampoline)
4. change orig impl to objc_msgForward
5. Custom forward handler calls hooks, changes invocation selector to interpose_
6. super handler in interpose changes _cmd back to expected and calls super

TODO:

• class-based not just objects (can't easily fix the selector then...
• pass on invocation + helpers to get parameters
• copy block parameters as needed
• check block type signature
• Generalize interpose _cmd filter

[codecov]

Codecov Report

Merging #19 into master will increase coverage by 1.58%.
The diff coverage is 86.51%.

@@            Coverage Diff             @@
##           master      #19      +/-   ##
==========================================
+ Coverage   83.09%   84.67%   +1.58%     
==========================================
  Files          15       18       +3     
  Lines         899     1057     +158     
==========================================
+ Hits          747      895     +148     
- Misses        152      162      +10     

Impacted Files	Coverage Δ
Sources/InterposeKit/InterposeError.swift	55.17% <50.00%> (-0.39%)	⬇️
Sources/InterposeKit/InterposeKit.swift	89.18% <62.50%> (+0.45%)	⬆️
Sources/InterposeKit/ObjectHook.swift	66.66% <62.50%> (+1.52%)	⬆️
Sources/InterposeKit/InterposeRuntime.swift	83.78% <83.78%> (ø)
Sources/SuperBuilder/src/ITKSuperBuilder.m	87.71% <85.71%> (-0.34%)	⬇️
Sources/InterposeKit/InterposeSubclass.swift	91.20% <86.95%> (-3.24%)	⬇️
Sources/InterposeKit/DynamicHook.swift	91.80% <91.80%> (ø)
Sources/InterposeKit/AnyHook.swift	75.60% <100.00%> (+1.25%)	⬆️
Sources/InterposeKit/ClassHook.swift	83.33% <100.00%> (-0.88%)	⬇️
Sources/InterposeKit/HookFinder.swift	96.77% <100.00%> (+0.34%)	⬆️
... and 5 more

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[crsantos]

Hey Peter, hope you're fine.

Honest question, was there any work left to do on this PR?
Because this would be an awesome feature ❤️