fix: pre-state tracer logging storage after call from precompile #64
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Why this should be merged
Fixes tracing when a stateful precompile calls another contract that itself accesses storage.
How this works
The pre-state tracer from
eth/tracers/nativedoesn't implementCaptureEnter()(entry of a new context), instead relying onCaptureState()(per-opcode tracing) to detect that a new contract has been entered. In doing so, it maintains an invariant that is expected whenCaptureState(vm.SLOAD, ...)is called—breaking the invariant results in a panic due to a nil map.The fix involves (a) maintaining the invariant as part of
CaptureEnter()(previously a no-op); and (b) calling said method insidevm.PrecompileEnvironment.Call(). The latter has the added benefit of properly handling all tracing involving an outbound call from precompiles.How this was tested
New integration test demonstrates that the tracer can log the retrieved storage value.