Added support for replacing game scripts

[zykurv]

Script replacements are configured with a new "replaceScripts" option in mkxp.json. Because you can have multiple scripts with the same names you can also specify using the script index instead.

[Splendide-Imaginarius]

What's the use case here? Is there a reason why preload/postload scripts would be less suitable? (Not saying I'm against this feature, just trying to understand the reasoning.)

[zykurv]

@Splendide-Imaginarius scripts aren't necessarily pure, they can have side effects... Which means a script that is causing a problem during load cannot be patched postload, because at that point the script side effects were already executed. And I don't think there'd be anything preload that can be done to avoid the faulty script from executing either.

There's also a problem I found in one case, where the inheritance of a class is changed after it was originally defined. This used to work in the Ruby version that RMVX uses, but causes an error with the version being used by mkxp-z. Because of that the game won't work, you need to replace the script to ensure the inheritance is consistent for all the class declarations.

[WaywardHeart]

And I don't think there'd be anything preload that can be done to avoid the faulty script from executing either.

@zykurv Preload scripts can access and modify the game scripts using the $RGSS_SCRIPTS global variable.

ensure the inheritance is consistent for all the class declarations

If I understand what you mean then that shouldn't actually be an issue for us. Our fork of ruby has a patch that removes that error.

[WaywardHeart]

@Splendide-Imaginarius I just did some testing, and in Ruby 1.8 you could actually change the super class by doing that - which we're not replicating. Do we want to change that? Ace games shouldn't be doing that at all, so we probably wouldn't be introducing any bugs by adding that functionality.

Edit: Scratch that, it doesn't change the super class, it generates a new class and replaces the constant.

[WaywardHeart]

Alright, I found the problem. It turns out Struma had tried to fix it, but had only removed the error in one of the code paths. I also included a fix for a syntax error I've ran into before. Thanks for bringing that to our attention @zykurv.

[zykurv]

@WaywardHeart oops sorry, I misremembered the issue. Yeah the issue was that "super()" was calling the functions from the wrong class after changing the inheritance. Thanks for investigating ^_^

[zykurv]

@zykurv Preload scripts can access and modify the game scripts using the $RGSS_SCRIPTS global variable.

Sorry, I didn't knew that... after some testing I was able to do the script replacement with the preload script below. Thanks for the info, I guess this PR is unneeded then.

$RGSS_REPLACE = {
    "GameScriptFoo" => "scripts/Foo.rb",
    "123" => "scripts/Bar.rb",
}

for index in 0...$RGSS_SCRIPTS.size
    script_info = $RGSS_SCRIPTS[index]
    script_name = script_info[1]

    replace_file = nil
    replace_file = $RGSS_REPLACE[index.to_s] if $RGSS_REPLACE[index.to_s] != nil
    replace_file = $RGSS_REPLACE[script_name] if $RGSS_REPLACE[script_name] != nil
    next if replace_file == nil

    File.open(replace_file, "r") do |file|
        script_info[3] = file.read
    end
end

[Splendide-Imaginarius]

@zykurv Would you be willing to submit a PR that adds that preload script to the scripts/preload folder? (Also I didn't know it was accessible that way either, thanks @WaywardHeart for the info!)

[zykurv]

@Splendide-Imaginarius PR opened here: https://github.com/mkxp-z/mkxp-z/pull/180