Implement a Custom Module Resolver

For many applications in which Rhai is embedded, it is necessary to customize the way that modules are resolved. For instance, modules may need to be loaded from script texts stored in a database, not in the file system.

A module resolver must implement the trait [rhai::ModuleResolver][traits], which contains only one function: resolve.

When Rhai prepares to load a module, ModuleResolver::resolve is called with the name of the module path (i.e. the path specified in the [import] statement). Upon success, it should return a [Module]; if the module cannot be load, return EvalAltResult::ErrorModuleNotFound.

Example

use rhai::{ModuleResolver, Module, Engine, EvalAltResult};

// Define a custom module resolver.
struct MyModuleResolver {}

// Implement the 'ModuleResolver' trait.
impl ModuleResolver for MyModuleResolver {
    // Only required function.
    fn resolve(
        &self,
        engine: &Engine,    // reference to the current 'Engine'
        path: &str,         // the module path
        pos: Position,      // position of the 'import' statement
    ) -> Result<Module, Box<EvalAltResult>> {
        // Check module path.
        if is_valid_module_path(path) {
            // Load the custom module.
            let module: Module = load_secret_module(path);
            Ok(module)
        } else {
            Err(EvalAltResult::ErrorModuleNotFound(path.into(), pos).into())
        }
    }
}

let mut engine = Engine::new();

// Set the custom module resolver into the 'Engine'.
engine.set_module_resolver(Some(MyModuleResolver {}));

engine.consume(r#"
    import "hello" as foo;  // this 'import' statement will call
                            // 'MyModuleResolver::resolve' with "hello" as path
    foo:bar();
"#)?;

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Implement a Custom Module Resolver

Example

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