How to Override the require Lua Function in C++ for Custom Script Loading

[gsisinna]

Hi,
I'm working on a project where I need to override the require function in Lua using C++.

My goal is to achieve the following:

1. Look up in a scripts map (C++): I have a map in C++ that contains script content and other flags (e.g., debug_mode = true/false). I want the require function to first check this map for the script.

2. Load at runtime: If the script is not found in the map, I want the require function to search for Lua scripts in a specified package path at runtime.
   (Without hard-coding this path in the Lua script, but from a config file I parse in C++).

Here are some examples to illustrate what I'm trying to achieve:

Lua Example:

-- Custom require function in Lua
function custom_require(name)
    -- Check the C++ map for the script
    local script = cpp_lookup_script(name)
    if script then
        return load(script)()
    end

    -- Fallback to the default require behavior
    return original_require(name)
end

-- Override the default require function
original_require = require
require = custom_require

C++ Example:

#include <sol/sol.hpp>
#include <unordered_map>
#include <string>

// Example script map
std::unordered_map<std::string, std::string> script_map = {
    {"example", "print('Hello from example script!')"}
};

// Function to look up scripts in the map
std::string cpp_lookup_script(const std::string& name) {
    auto it = script_map.find(name);
    if (it != script_map.end()) {
        return it->second;
    }
    return "";
}

int main() {
    sol::state lua;
    lua.open_libraries(sol::lib::base);

    // Expose the C++ lookup function to Lua
    lua.set_function("cpp_lookup_script", cpp_lookup_script);

    // Load and execute the Lua script that overrides require
    lua.script(R"(
        original_require = require
        function custom_require(name)
            local script = cpp_lookup_script(name)
            if script ~= "" then
                return load(script)()
            end
            return original_require(name)
        end
        require = custom_require
    )");

    // Test the custom require function
    lua.script(R"(
        require('example')
    )");

    return 0;
}

Could you provide guidance or examples on how to implement this correctly in sol2?

Thank you!

[Perl99]

Maybe this example will be helpful: https://github.com/ThePhD/sol2/blob/develop/examples/source/require_override_behavior.cpp

[gsisinna]

Maybe this example will be helpful: develop/examples/source/require_override_behavior.cpp

Thank you very much, after some trials I was able to overload the require function and return scripts from a custom map in C++ 💯