How push new ObjectProperty to program AST in Rust

[shahryarjb]

Hi friends, I need help adding an empty object to a key, like "hooks," in Rust. I've been stuck on this for three days due to my limited knowledge as a Rust beginner.

---

Please take a look at the function below. Ignore most of the code except for the last few lines, where I'm trying to add an empty object I've created to the existing ast.

fn find_hooks_property<'short, 'long>(
    program: &'short mut Program<'long>,
    allocator: &'short Allocator,
) -> Result<Option<&'short mut Expression<'long>>, String> {
    let live_socket_found = program.body.iter_mut().any(|node| {
        if let Statement::VariableDeclaration(var_decl) = node {
            var_decl
                .declarations
                .iter()
                .any(|decl| is_target_variable(decl, "liveSocket"))
        } else {
            false
        }
    });

    if !live_socket_found {
        return Err("liveSocket not found.".to_string());
    }

    let result = program.body.iter_mut().find_map(|node| {
        let var_decl = match node {
            Statement::VariableDeclaration(var_decl) => var_decl,
            _ => return None,
        };

        var_decl.declarations.iter_mut().find_map(|decl| {
            let obj_expr = get_new_expression(decl)?;

            obj_expr.arguments.iter_mut().find_map(|arg| {
                let obj_expr_inner = get_object_expression(arg)?;
                let mut iter = obj_expr_inner.properties.iter_mut();
                if let Some(expr) = iter.find_map(|prop| get_property_by_key(prop, "hooks")) {
                    return Some(expr);
                }

                let new_hooks_property = ObjectPropertyKind::ObjectProperty(OXCBox::new_in(
                    ObjectProperty {
                        span: Span::default(),
                        kind: PropertyKind::Init,
                        key: PropertyKey::StaticIdentifier(OXCBox::new_in(
                            IdentifierName {
                                span: Span::default(),
                                name: Atom::from("hooks"),
                            },
                            allocator,
                        )),
                        value: Expression::ObjectExpression(OXCBox::new_in(
                            ObjectExpression {
                                span: Span::default(),
                                properties: OXCVec::new_in(allocator),
                                trailing_comma: None,
                            },
                            allocator,
                        )),
                        method: false,
                        shorthand: false,
                        computed: false,
                    },
                    allocator,
                ));

                iter.push(new_hooks_property)
                // .find_map(|prop| get_property_by_key(prop, "hooks"))
            })
        })
    });

    Ok(result)
}

I mean this line: iter.push(new_hooks_property). However, iter doesn’t support push here. I've tried several other approaches, but unfortunately, I keep running into errors, including lifetime issues and more.

---

magine what I’m trying to do is as follows:

In a JavaScript file, we have lines like this:

let liveSocket = new LiveSocket("/live", Socket, {
  longPollFallbackMs: 2500,
  params: { _csrf_token: csrfToken },
});

I want to check if the liveSocket variable contains a hooks key. If it doesn’t, I want to add one with an empty object, so it becomes:

let liveSocket = new LiveSocket("/live", Socket, {
  hooks: {},
  longPollFallbackMs: 2500,
  params: { _csrf_token: csrfToken },
});

If hooks already exists, I don’t need to do anything and just return it as is.

This is the entire function I've written for this simple task, but unfortunately, I haven't been able to complete it. I thought perhaps I could use your help:

https://github.com/shahryarjb/mishka_chelekom/blob/a3ae62b8b1eaca5fbe66ed66bfc00c3be29e24a3/native/mishka_parser_nif/src/parser/ast.rs#L170-L324

Thank you in advance

[Boshen]

It should be obj_expr_inner.properties.push. Things are not going to work as expected because your code is mixing up mutability.

[shahryarjb]

@Boshen
Sorry to ask again, but do you also use this same approach with consecutive conditions for modifying the AST of a JS file, or do you rely on another, easier method using the functionalities provided by the library? could you give me an example if exist?
Thank you!