Example prevent-circular: Cannot resolve binding

[dotai2012]

Version: 0.4.1 Problem:

Error: BindingResolveFailed { reason: ResolveFailed { reason: BindingResolveFailed { reason: ResolveFailed { reason: BindingResolveFailed { reason: DetectedCircular { dependency_history: DependencyHistory { inner: ["creditor::Foo", "creditor::Bar", "creditor::Foo"] } }, interface: "creditor::Foo" }, affected: "creditor::Bar" }, interface: "creditor::Bar" }, affected: "creditor::Foo" }, interface: "creditor::Foo" }

How to reproduce: This is the code I copied exactly from the example (https://git.hampusmat.com/syrette/tree/examples/prevent-circular)

#![deny(clippy::all)]
#![deny(clippy::pedantic)]
#![allow(clippy::disallowed_names)]
use std::error::Error;

use syrette::di_container::blocking::prelude::*;
use syrette::injectable;
use syrette::ptr::TransientPtr;

struct Foo
{
    bar: TransientPtr<Bar>,
}

#[injectable]
impl Foo
{
    fn new(bar: TransientPtr<Bar>) -> Self
    {
        Self { bar }
    }
}

struct Bar
{
    foo: TransientPtr<Foo>,
}

#[injectable]
impl Bar
{
    fn new(foo: TransientPtr<Foo>) -> Self
    {
        Self { foo }
    }
}

fn main() -> Result<(), anyhow::Error>
{
    let mut di_container = DIContainer::new();

    di_container.bind::<Foo>().to::<Foo>()?;
    di_container.bind::<Bar>().to::<Bar>()?;

    let foo = di_container.get::<Foo>()?.transient()?;

    Ok(())
}

[HampusMat]

This is the expected behaviour of this example. Should i maybe add comments to explain it?

[dotai2012]

Oh, I see, so it's expected, I think we can add a comment in the code 😅

Btw, how can I bind Bar to Bar (without a trait)

Something like:

struct Bar
{}

#[injectable]
impl Bar
{
    fn new() -> Self
    {
        Self { }
    }
}

fn main() -> Result<(), Box<dyn Error>>
{
    let mut di_container = DIContainer::new();

    di_container.bind::<Bar>().to::<Bar>()?;

    let bar = di_container.get::<Bar>()?.transient()?;

    Ok(())
}

I got an error:

Error: CastFailed { interface: "creditor::Bar", binding_kind: "transient" }

Or do I have to use the factory feature?

[HampusMat]

I honestly haven't though much about that use case. Using a trait should be preferred in my opinion. But if you for any reason would want to, you could use a default factory

[dotai2012]

So my codebase has a global Config struct -> it doesn't have any methods (so no trait)

Other services will use that global config

This workflow is very easy to do in Go (Uber Fx or Google wire)

Could it be achievable without using the factory? (because of Rust nightly)

[HampusMat]

I realize now that it actually should be possible to bind a struct to itself. So i have no idea why it doesn't work. I will look into it a bit later today.

[HampusMat]

Basically what Syrette does deep down is it downcasts types using the downcast methods of either Box, Rc or Arc. In this case it would be Box.

And the downcast method of Box is basically:

if self.is::<T>() {
    unsafe {
        let (raw, alloc): (*mut dyn Any, _) =
            Box::into_raw_with_allocator(self);

        Ok(Box::from_raw_in(raw as *mut T, alloc))
    }
}
else {
    Err(self)
}

So it would maybe be if self.is::<T>() returns false. But that makes no sense as it is literally the same type.

But as i said, i will look into this later. I just wanted to quickly throw this out there.

[HampusMat]

I found the problem and fixed it in e282375de4ba75c69f7d619fc33c6250f6caba18.

It was because no interface was being declared. The injectable attribute macro declares the interface with the declare_interface macro when a interface argument is given to it. So because no interface argument was given, it didn't do that. So i made it by default declare the concrete type as the interface when no interface argument is given.

[HampusMat]

Oh, and i added some comments to the prevent-circular example in 488faf96336711a527a3610c728a2409087b69fa.

[HampusMat]

Thank you so much for the help! :)

[dotai2012]

Thank you so much @HampusMat

This is the best DI lib. I've already starred your repo

[dotai2012]

Btw, I think we also need to update:

https://github.com/HampusMat/Syrette/blob/3c993aa73c93f0fe335ced78d9709b39cdbd1935/src/di_container/asynchronous/mod.rs#L249

[HampusMat]

Btw, I think we also need to update:

https://github.com/HampusMat/Syrette/blob/3c993aa73c93f0fe335ced78d9709b39cdbd1935/src/di_container/asynchronous/mod.rs#L249

Why exactly? I can't see how that line would cause any problems.

[dotai2012]

Yes, I think right now we point to a struct directly, but the param requires Send + Sync

File to reproduce:

async.zip