precompiler.jl

options_path = "src/options.h"
if !isfile(options_path)
    error("current working dir must be the julia directory")
end
println("Welcome to the custom precompile statement builder")
sleep(1)
println("First we will rebuild julia to emit what functions it compile")
sleep(1)

options = read(options_path, String)
write(options_path, replace(options, "//#define TRACE_COMPILE" => "#define TRACE_COMPILE"))
run(`make -j4`)

println("Now we will record all functions used by julia when it starts up")
sleep(1)
println("Feel free to play around a bit in the REPL as well, exit the started julia when done")
run(pipeline(`./julia`; stderr="precompile.txt"))


println("Precompile statements written, recompiling julia with the new statements!")
sleep(1)
precompiles = readlines("base/precompile.jl")
new_precompiles = String[]

for p in readlines("precompile.txt")
    if startswith(p, "precompile")
        push!(new_precompiles, p)
    end
end

# Two last lines in precompile.jl are end of modules.
# Insert before those
i = length(precompiles) - 3
precompiles_after = [precompiles[1:i]; new_precompiles; precompiles[i+1:end]]
write("base/precompile.jl", join(precompiles_after, '\n'))

write(options_path, replace(options, "#define TRACE_COMPILE" => "//#define TRACE_COMPILE"))
run(`make -j4`)
println("Please restart julia and enjoy a snappier REPL")