New spell language

[AltimorTASDK]

The new language can be used by using a .spell extension instead of .json
Example rewrite of Gong Strike:

identifier = "gong_strike";
loc_name = "Gong Strike";
max_lvl = 16;
min_lvl = 1;
statsForSkillGem = [
    { type = "FLAT"; min = 15.0; max = 30.0; stat = "endurance_charge_on_hit"; }
];

cast_finish_animation id = "spell_taunt";

config {
    tags tags = ["weapon_skill", "damage", "melee", "physical"];
    castingWeapon = "MELEE_WEAPON";
    style = "str";
    cast_time_ticks = 0;
    cooldown_ticks = 40;
    ene_cost { min = 6.0; max = 8.0; }
    mana_cost { min = 1.0; max = 2.0; }
    swing_arm = false;
}

on_cast {
    // note the omitted semicolons; these are combined into one spell component part
    sound("roe_sfx:spell_gongstrike", 1.0)
    sound("roe_sfx:spell_hit_heavy", 1.0)
    particles_in_radius("minecraft:cloud", radius=2.0, particle_count=300.0, shape="CIRCLE_2D", height=0.5, y_rand=0.1)
    particles_in_radius("minecraft:explosion", radius=2.0, particle_count=5.0, shape="CIRCLE_2D", height=0.5, y_rand=0.1);

    if (caster_has_mns_effect("fighter_stance")) {
        select (in_front(5.0, 2.5, "enemies")) {
            damage("Physical", "gong_strike_fighter", disable_knockback=true);
        }
    } else if (caster_has_mns_effect("defender_stance")) {
        select (in_front(4.0, 2.0, "enemies")) {
            damage("Physical", "gong_strike", disable_knockback=true)
            exile_effect("stun", 1.0, "GIVE_STACKS", 10.0);
        }
    } else {
        select (in_front(4.0, 2.0, "enemies")) {
            damage("Physical", "gong_strike_plain", disable_knockback=true);
        }
    }
}

Significant features not showcased are combining conditions with &&, inverting conditions (is_false shouldn't be used directly), adding en_preds, and per_entity_hit:

if (caster_has_mns_effect("defender_stance") && !en.has_mns_effect("slow")) {
    damage("Physical", "primary_hit", disable_knockback=true) per_entity_hit {
        select (aoe(3.0, "enemies")) damage("Physical", "secondary_hit", disable_knockback=true)
    }
}

Selectors can also be combined with ||:

select (in_front(5.0, 2.5, "enemies") || aoe(3.0, "enemies")) {
    /* ... */
}

Oh yeah and entities:

entity my_sick_entity {
    if (x_ticks_condition(5.0)) {
        // idk do somethin
    }
}

Requires mahjerion/Library-of-Exile-Rework#8

KNOWN ISSUE: constructs like if (!(cond1() && cond2())) or if (cond1() && cond2()) { } else { } don't work properly because mns doesn't yet support OR in conditions, which this is equivalent to

[AltimorTASDK]

gonna add || to if conditions and fix the wrong behavior when inverting compound conditions