Bug Report

Cairo version: 2.6.3

Current behavior:

When creating a struct instance, there is no completion dialog support - the one that does appear contains some values that can only be described as random.

Example 1: struct in the same module:

Example 2: public struct in a different module with a public field:

Example 3: public struct in a different module with a private field:

Expected behavior:

Completion dialog for struct instances should only list its available fields and nothing else.

Expected for examples above: Example 1: struct in the same module - should only list field. Example 2: public struct in a different module with a public field - should only list field_2. Example 3: public struct in a different module with a private field - should list nothing.

Steps to reproduce:

create a new Scarb package
open lib.cairo in VS Code (ensure Cairo 1.0 extension is installed)
paste the code from "Related code" section below into the opened file
put the cursor inside any of the struct instance creation expressions (between curly brackets)
prompt the completion dialog to open (usually CTRL + Space)

Related code:

#[derive(Drop)]
struct Type {
    field: felt252,
}

mod some_mod {
    #[derive(Drop, Debug)]
    pub struct SomeType {
        pub field_2: felt252
    }
}

mod another_mod {
    #[derive(Drop, Debug)]
    pub struct AnotherType {
        field_3: felt252
    }
}

fn main() {
    let struct_instance = Type {
        
    };
    let struct_instance_2 = some_mod::SomeType {
        
    };
    let struct_instance_3 = another_mod::AnotherType {
        
    };
}

Other information:

Related issue: https://github.com/starkware-libs/cairo/issues/5660

May 28 '24 08:05 0xNeshi

Hello @misicnenad, I would like to help with this one if possible!

Jun 08 '24 04:06 danielcdz

@danielcdz awesome, please check with @mkaput if he can assign this to you

Jun 08 '24 09:06 0xNeshi

ty @misicnenad, hey @mkaput can I help with this?

Jun 08 '24 16:06 danielcdz

@danielcdz yes of course! Task is assigned to you :) Thanks 💖

Jun 10 '24 07:06 mkaput

Hey @mkaput this is similar to #5660, can I follow the same instructions you left in the comments?

Jun 11 '24 03:06 danielcdz

Hey @mkaput this is similar to #5660, can I follow the same instructions you left in the comments?

I think so

Jun 11 '24 07:06 mkaput

@danielcdz hey, how's it going? Would you like some assistance from my side in this area?

Jun 17 '24 09:06 mkaput

@mkaput that would be great! I would write some questions below 👇

Jun 17 '24 16:06 danielcdz

I'm trying to look where the completions for a struct are being made but I didn't find anything useful, I saw that on issue #5660 you left some comments with examples of where completions are computed, can you help me with something similar for this 🙏

Jun 18 '24 02:06 danielcdz

It looks like you have to add a new completion kind for struct fields, here:

https://github.com/starkware-libs/cairo/blob/88f0506651106300e3d05bb3adf9eef0ee77ff24/crates/cairo-lang-language-server/src/ide/completion/mod.rs#L68-L149

This is basically traversing AST up to learn where you are. So you have to check out if you are within braces ({}) of struct construction expression. I guess either the left brace, or comma would be the nodes that you get at the input, but this is an exercise for you to investigate :)

Then, you have to hook completion implementation, starting here add a clause for your new completion kind:

https://github.com/starkware-libs/cairo/blob/88f0506651106300e3d05bb3adf9eef0ee77ff24/crates/cairo-lang-language-server/src/ide/completion/mod.rs#L45-L57

The body of this function is pretty wild west now. You have to get the semantic model of the struct that you are completing. I think you can find a lot of logic to copy in dot completions (i.e. foobar.<complete>), here:

https://github.com/starkware-libs/cairo/blob/57ffe1893a351f587e648e530ba0deb97e853ed8/crates/cairo-lang-language-server/src/ide/completion/completions.rs#L182-L254

For example, this is the function to get struct members (concrete, i.e. with generic parameters resolved to concrete types according to type inference context): https://github.com/starkware-libs/cairo/blob/448c234a612d9012b118f260ca47bcd33425f7d0/crates/cairo-lang-semantic/src/items/structure.rs#L260-L284

Jun 18 '24 07:06 mkaput

Hey @mkaput ty for all the explanations you gave me, I think I got the main idea on how to solve it, but I prefer to let this issue to a person more experienced in Rust, also I'm participating in a Hackathon and I don't have enough time to solve this issue at the moment, I'm sorry for this 😞

Jun 20 '24 04:06 danielcdz

@danielcdz understood :)

I think I got the main idea on how to solve it

Do you think you can add your own two cents to this? This would be a great contribution on its own! 😍

Jun 20 '24 08:06 mkaput

@KevinMB0220 feel free to submit a PR. We're not assigning tasks to external contributors anymore

Aug 30 '24 12:08 mkaput

bug: LSP completion dialog should only recommend members of a struct

Bug Report