How to test an app at the REPL

New to Julia
1

Say, I want to develop a standalone, compiled application; after reading about various options, I settled on creating a project via Pkg.generate.

Now, I have a project structure with Manifest.toml and Project.toml files, and the program entry point under MyProgram/src/MyProgram.jl

At this very moment, all the program does is parse command line arguments; let’s say MyProgram.jl looks like this:

module MyProgram
    using ArgParse
    function main()
    ...
    end
end

This minimal program:

  • compiles fine with PackageCompiler.create_app()
  • runs from the command line just fine and correctly processes command line arguments

What are the steps that I need to take to end up at the REPL with the correct environment, so that I can easily edit my program and test it over and over? Meaning, without having to re-start Julia?

In particular, I would like to change the “comand line arguments” (while in REPL) and call main() over and over.

2

There may be a way to do what you want, but when faced with this problem in the past, I have changed the structure of the code to make REPL work simpler.

module MyProgram
using ArgParse

function do_stuff(args)
  # This function is the top-level of the program's functionality
  # and is easily called from the REPL
end

function parse_args()
  # Argument parsing happens here, this returns a parsed args structure
  # that can be passed to do_stuff()
end

function main()
  args = parse_args()
  do_stuff(args)
end

end

If creating args manually get tedious, it is often helpful to write some tools to create a starting point, I often create a test/REPL_tests.jl that has functions to mock up useful sets of args and then includet that file.

3

If you want to change the command line arguments while Julia is running, you can edit the variable ARGS.
Trying to assign a value to the variable probably won’t do what you want, but this should work:

clear!(ARGS)
append!(ARGS, ["foo", "--bar"])
4

For an example:

julia> using ArgMacros

julia> function main()
           @beginarguments begin
               @argumentflag verbose "-v"
               @positionaldefault Int 1 x
           end

           println(x, verbose)
       end
main (generic function with 1 method)

julia> ARGS
0-element Array{String,1}

julia> main()
1false

julia> append!(ARGS, ["3", "-v"])
2-element Array{String,1}:
 "3"
 "-v"

julia> main()
3true

julia> empty!(ARGS)
0-element Array{String,1}

julia> push!(ARGS, "4")
1-element Array{String,1}:
 "4"

julia> main()
4false
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