rhai/tests/custom_syntax.rs

#![cfg(not(feature = "no_custom_syntax"))]

use rhai::{
    Dynamic, Engine, EvalAltResult, ImmutableString, LexError, ParseErrorType, Position, Scope, INT,
};

#[test]
fn test_custom_syntax() -> Result<(), Box<EvalAltResult>> {
    let mut engine = Engine::new();

    engine.run("while false {}")?;

    // Disable 'while' and make sure it still works with custom syntax
    engine.disable_symbol("while");
    assert!(matches!(
        engine.compile("while false {}").expect_err("should error").err_type(),
        ParseErrorType::Reserved(err) if err == "while"
    ));
    assert!(matches!(
        engine.compile("let while = 0").expect_err("should error").err_type(),
        ParseErrorType::Reserved(err) if err == "while"
    ));

    // Implement ternary operator
    engine.register_custom_syntax(
        ["iff", "$expr$", "?", "$expr$", ":", "$expr$"],
        false,
        |context, inputs| match context.eval_expression_tree(&inputs[0])?.as_bool() {
            Ok(true) => context.eval_expression_tree(&inputs[1]),
            Ok(false) => context.eval_expression_tree(&inputs[2]),
            Err(typ) => Err(Box::new(EvalAltResult::ErrorMismatchDataType(
                "bool".to_string(),
                typ.to_string(),
                inputs[0].position(),
            ))),
        },
    )?;

    assert_eq!(
        engine.eval::<INT>(
            "
                let x = 42;
                let y = iff x > 40 ? 0 : 123;
                y
            "
        )?,
        0
    );

    assert_eq!(
        engine.eval::<INT>(
            "
                let x = 42;
                let y = iff x == 0 ? 0 : 123;
                y
            "
        )?,
        123
    );

    // Custom syntax
    engine.register_custom_syntax(
        [
            "exec", "[", "$ident$", "$symbol$", "$int$", "]", "->", "$block$", "while", "$expr$",
        ],
        true,
        |context, inputs| {
            let var_name = inputs[0].get_string_value().unwrap();
            let op = inputs[1].get_literal_value::<ImmutableString>().unwrap();
            let max = inputs[2].get_literal_value::<INT>().unwrap();
            let stmt = &inputs[3];
            let condition = &inputs[4];

            context.scope_mut().push(var_name.to_string(), 0 as INT);

            let mut count: INT = 0;

            loop {
                let done = match op.as_str() {
                    "<" => count >= max,
                    "<=" => count > max,
                    ">" => count <= max,
                    ">=" => count < max,
                    "==" => count != max,
                    "!=" => count == max,
                    _ => return Err(format!("Unsupported operator: {op}").into()),
                };

                if done {
                    break;
                }

                // Do not rewind if the variable is upper-case
                if var_name.to_uppercase() == var_name {
                    context.eval_expression_tree_raw(stmt, false)?;
                } else {
                    context.eval_expression_tree(stmt)?;
                }

                count += 1;

                context
                    .scope_mut()
                    .push(format!("{var_name}{count}"), count);

                let stop = !context
                    .eval_expression_tree(condition)?
                    .as_bool()
                    .map_err(|err| {
                        Box::new(EvalAltResult::ErrorMismatchDataType(
                            "bool".to_string(),
                            err.to_string(),
                            condition.position(),
                        ))
                    })?;

                if stop {
                    break;
                }
            }

            Ok(count.into())
        },
    )?;

    assert!(matches!(
        *engine
            .run("let foo = (exec [x<<15] -> { x += 2 } while x < 42) * 10;")
            .expect_err("should error"),
        EvalAltResult::ErrorRuntime(..)
    ));

    assert_eq!(
        engine.eval::<INT>(
            "
                let x = 0;
                let foo = (exec [x<15] -> { x += 2 } while x < 42) * 10;
                foo
            "
        )?,
        150
    );
    assert_eq!(
        engine.eval::<INT>(
            "
                let x = 0;
                exec [x<100] -> { x += 1 } while x < 42;
                x
            "
        )?,
        42
    );
    assert_eq!(
        engine.eval::<INT>(
            "
                exec [x<100] -> { x += 1 } while x < 42;
                x
            "
        )?,
        42
    );
    assert_eq!(
        engine.eval::<INT>(
            "
                let foo = 123;
                exec [x<15] -> { x += 1 } while x < 42;
                foo + x + x1 + x2 + x3
            "
        )?,
        144
    );
    assert_eq!(
        engine.eval::<INT>(
            "
                let foo = 123;
                exec [x<15] -> { let foo = x; x += 1; } while x < 42;
                foo
            "
        )?,
        123
    );
    assert_eq!(
        engine.eval::<INT>(
            "
                let foo = 123;
                exec [ABC<15] -> { let foo = ABC; ABC += 1; } while ABC < 42;
                foo
            "
        )?,
        14
    );

    // The first symbol must be an identifier
    assert_eq!(
        *engine
            .register_custom_syntax(["!"], false, |_, _| Ok(Dynamic::UNIT))
            .expect_err("should error")
            .err_type(),
        ParseErrorType::BadInput(LexError::ImproperSymbol(
            "!".to_string(),
            "Improper symbol for custom syntax at position #1: '!'".to_string()
        ))
    );

    // Check self-termination
    engine
        .register_custom_syntax(["test1", "$block$"], true, |_, _| Ok(Dynamic::UNIT))?
        .register_custom_syntax(["test2", "}"], true, |_, _| Ok(Dynamic::UNIT))?
        .register_custom_syntax(["test3", ";"], true, |_, _| Ok(Dynamic::UNIT))?;

    assert_eq!(engine.eval::<INT>("test1 { x = y + z; } 42")?, 42);
    assert_eq!(engine.eval::<INT>("test2 } 42")?, 42);
    assert_eq!(engine.eval::<INT>("test3; 42")?, 42);

    // Register the custom syntax: var x = ???
    engine.register_custom_syntax(
        ["var", "$ident$", "=", "$expr$"],
        true,
        |context, inputs| {
            let var_name = inputs[0].get_string_value().unwrap();
            let expr = &inputs[1];

            // Evaluate the expression
            let value = context.eval_expression_tree(expr)?;

            if !context.scope().is_constant(var_name).unwrap_or(false) {
                context.scope_mut().set_value(var_name.to_string(), value);
                Ok(Dynamic::UNIT)
            } else {
                Err(format!("variable {var_name} is constant").into())
            }
        },
    )?;

    let mut scope = Scope::new();

    assert_eq!(
        engine.eval_with_scope::<INT>(&mut scope, "var foo = 42; foo")?,
        42
    );
    assert_eq!(scope.get_value::<INT>("foo"), Some(42));
    assert_eq!(scope.len(), 1);
    assert_eq!(
        engine.eval_with_scope::<INT>(&mut scope, "var foo = 123; foo")?,
        123
    );
    assert_eq!(scope.get_value::<INT>("foo"), Some(123));
    assert_eq!(scope.len(), 1);

    Ok(())
}

#[test]
fn test_custom_syntax_raw() -> Result<(), Box<EvalAltResult>> {
    let mut engine = Engine::new();

    engine.register_custom_syntax_raw(
        "hello",
        |stream, _| match stream.len() {
            0 => unreachable!(),
            1 => Ok(Some("$ident$".into())),
            2 => match stream[1].as_str() {
                "world" => Ok(Some("$$hello".into())),
                "kitty" => Ok(None),
                s => Err(LexError::ImproperSymbol(s.to_string(), String::new())
                    .into_err(Position::NONE)
                    .into()),
            },
            _ => unreachable!(),
        },
        true,
        |context, inputs| {
            context.scope_mut().push("foo", 999 as INT);

            Ok(match inputs[0].get_string_value().unwrap() {
                "world"
                    if inputs
                        .last()
                        .unwrap()
                        .get_literal_value::<ImmutableString>()
                        .map_or(false, |s| s == "$$hello") =>
                {
                    0 as INT
                }
                "world" => 123 as INT,
                "kitty" if inputs.len() > 1 => 999 as INT,
                "kitty" => 42 as INT,
                _ => unreachable!(),
            }
            .into())
        },
    );

    assert_eq!(engine.eval::<INT>("hello world")?, 0);
    assert_eq!(engine.eval::<INT>("hello kitty")?, 42);
    assert_eq!(
        engine.eval::<INT>("let foo = 0; (hello kitty) + foo")?,
        1041
    );
    assert_eq!(engine.eval::<INT>("(hello kitty) + foo")?, 1041);
    assert_eq!(
        *engine
            .compile("hello hey")
            .expect_err("should error")
            .err_type(),
        ParseErrorType::BadInput(LexError::ImproperSymbol("hey".to_string(), "".to_string()))
    );

    Ok(())
}

#[test]
fn test_custom_syntax_raw2() -> Result<(), Box<EvalAltResult>> {
    let mut engine = Engine::new();

    engine.register_custom_syntax_raw(
        "#",
        |symbols, lookahead| match symbols.len() {
            1 if lookahead == "-" => Ok(Some("$symbol$".into())),
            1 => Ok(Some("$int$".into())),
            2 if symbols[1] == "-" => Ok(Some("$int$".into())),
            2 => Ok(None),
            3 => Ok(None),
            _ => unreachable!(),
        },
        false,
        move |_, inputs| {
            let id = if inputs.len() == 2 {
                -inputs[1].get_literal_value::<INT>().unwrap()
            } else {
                inputs[0].get_literal_value::<INT>().unwrap()
            };
            Ok(id.into())
        },
    );

    assert_eq!(engine.eval::<INT>("#-1")?, -1);
    assert_eq!(engine.eval::<INT>("let x = 41; x + #1")?, 42);
    #[cfg(not(feature = "no_object"))]
    assert_eq!(engine.eval::<INT>("#-42.abs()")?, 42);
    assert_eq!(engine.eval::<INT>("#42/2")?, 21);
    assert_eq!(engine.eval::<INT>("sign(#1)")?, 1);

    Ok(())
}