A macro to show the callstack inside a function call.

callstack.jl

module CallStack

export @callstack

using Cassette

mutable struct CallState
    depth::Int
end

Cassette.@context CallContext

function Cassette.prehook(ctx::CallContext, f, args...)
    state = ctx.metadata
    if !(f isa Core.Builtin)
        print("  "^state.depth)
        display(first(methods(f, typeof.(args))))
    end
    state.depth += 1
end

function Cassette.posthook(ctx::CallContext, f, args...)
    state = ctx.metadata
    state.depth -= 1
end

macro callstack(ex)
    quote
        state = CallState(0)
        Cassette.overdub(CallContext(metadata=state), () -> $(esc(ex)))
    end
end

end

# Example
# -------

foo() = 1
bar() = foo()
baz() = bar()

# julia> using .CallStack
# 
# julia> @callstack baz();
# baz() in Main at /Users/kenta/workspace/julia/callstack.jl:41
#   bar() in Main at /Users/kenta/workspace/julia/callstack.jl:40
#     foo() in Main at /Users/kenta/workspace/julia/callstack.jl:39