Revise and const values changed during a session?

General Usage
3

Thank you so much! Today I have prepared a little test comparing your solution and another idea I had involving mutable structs. Your solution is by far the best (even better the not-working one).

Here the code and tests:

# A.jl
module A

# METHOD 1
# the following works but are not re-evaluated by Revise
const a = 5
b = 5

# METHOD 2
# functions are re-evaluated by Revise when they are changed
const c() = 5
d() = 5

# METHOD 3
mutable struct S
    vars::NamedTuple
    function S()
        # the following ensures that S cannot be reinstantiated without explicit
        # usage of `eval`
        isdefined(S, :s) && error("Cannot instantiate S twice")
        return new()
    end
end

# `const` ensures that the reference to the object will always be the same
const s = S()

# an easier way to get the settings
function getS()
    return s.vars
end

# defining fields in a function allows Revise to re-evaluate it when settings
# are changed
function init()
    s.vars = (a = 5, b = 5)
end

end


# B.jl
module B
using Main.A: a, b, c, d, getS
function test1()
    r = 0
    for i in 1:1000
        r += a + b
    end
    return r
end
function test2()
    r = 0
    for i in 1:1000
        r += c() + d()
    end
    return r
end
function test3()
    s = getS()
    r = 0
    for i in 1:1000
        r += s.a + s.b
    end
    return r
end
end

# C.jl
module C
using BenchmarkTools
using Main.B: test1, test2, test3
using Main.A: init


function main()
    init()
    println(@btime test1())
    println(@btime test2())
    println(@btime test3())
end
end

# D.jl
using Revise

includet("A.jl")
includet("B.jl")
includet("C.jl")

And here the tests:

julia> include("D.jl");

julia> C.main()
k  30.400 μs (958 allocations: 14.97 KiB)
12000
  1.492 ns (0 allocations: 0 bytes)
12000
  62.388 μs (958 allocations: 14.97 KiB)
12000

julia> C.main() # re-run after having  changed the settings
  30.289 μs (958 allocations: 14.97 KiB)
12000
  1.492 ns (0 allocations: 0 bytes)
10000
  62.629 μs (949 allocations: 14.83 KiB)
10000

As you see, method 1 doesn’t work on re-evaluation, method 3 works but is 2x slower, while method 2 works and is 20.000x faster

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