How to test a visitor that uses visit_mut_script

[leafypout]

Let's say you have a visitor, something like this

struct Visitor;

impl VisitMut for Visitor {
    fn visit_mut_script(&mut self, script: &mut Script) {
        // Do something with script
    }
}

Then you create a unit test, something like

#[test]
fn test_visitor() {
    let input = "";
    let expected = "";

    test_transform(Syntax::default(), |_| as_folder(&mut Visitor), input, expected, true);

    // Optionally do some assertions with assert, assert_eq etc on the visitor
}

The test function won't work because the internal code for test_transform parses the input code as a module and not a script, so visit_mut_script is never called. Is there a different function to use instead of test_transform or is there a way to make test_transform use parse_script instead of parse_module?

[lubieowoce]

For anyone else stumbling upon this, test_transform takes an is_module argument now:

pub fn test_transform<F, P>(
    syntax: Syntax,
    is_module: Option<bool>,
    tr: F,
    input: &str,
    expected: &str,
)
where
    F: FnOnce(&mut Tester<'_>) -> P,
    P: Pass,

https://rustdoc.swc.rs/swc_ecma_transforms_testing/fn.test_transform.html

[leafypout]

Yep, I made a PR for this a while ago back when I first had this issue. None will make it use parse_program, Some(true) will make it use parse_module and Some(false) will make it use parse_script.

[leafypout]

Also given this change you should probably just make your visitor use visit_mut_program instead.