OpenDAL Compat

[Xuanwo]

Hi, OpenDAL occasionally releases breaking changes. Each time this happens, our users need to update their versions. It's straightforward if users only depend on opendal itself.

However, since opendal is widely used, it's possible that users also depend on crates like iceberg, parquet, and delta, which depend on opendal as well. Those projects might have different release schedules that can't align with opendal's release.

Releasing opendal 1.0 might help, but it still needs time. Even opendal 1.0 can't fully address this, as not every crate can update to the new version promptly.

So I propose a new crate called opendal_compat. In which, we provide API like:

#[feature("v50_to_v49")]
fn v50_to_v49(v: opendal_v50::Operator) -> opendal_v49::Operator { ... }

This way, users can always convert the newer opendal versions to the old ones for compatibility.

---

The conversation isn't endless: we might only provide the two most recent major versions.

[yuchanns]

Sounds Cool

[morristai]

This is a great workaround to mitigate this issue. However, would it be possible to provide this kind of implementation so the user doesn't have to call the API explicitly every time?

impl From<opendal_v50::Operator> for opendal_v49::Operator {
    fn from(op: opendal_v50::Operator) -> Self {
        // Conversion logic
    }
}

[Xuanwo]

I explicitly intend to clarify that users are performing conversions between different versions of OpenDAL.

And, it's important to note that these operations are not zero-cost; each one requires a conversion, such as opendal_v50::OpRead -> opendal_v49::OpRead.

I don't want users to blindly perform such conversions.

[morristai]

Understood, then it's best to do it with an explicit function.