fix(foundationdb): make the db_run non capturing

[Akanoa]

Hello 👋

I would like to introduce a modification in the Database::run parameters signature.

The function is great, but there is a little flaw with the maybe_committed closure parameter. As this one is a boolean which is "copiable".

Therefore, if you want to use this parameter, you have to make the closure capturing.

db.run(|trx, maybe_committed| async move {
    if maybe_committed {
        // treatment
    }
    Ok(())
})
.await

But sometimes this behavior is not desired. For example, when, your closure uses an immutable reference of a variable in the outer environment.

#[derive(Debug)]
struct Data;
let data = Data;

db.run(|trx, maybe_committed| async move {
    if maybe_committed {
        // treatment
    }
    dbg!(&data)
    Ok(())
})
.await

With the error:

cannot move out of `data`, a captured variable in an `Fn` closure

There are two ways to making it functional

By using an Arc

#[derive(Debug)]
struct Data;

let data = Arc::new(Data);

db.run(|trx, maybe_committed| {
    let data = data.clone();

    async move {
        if maybe_committed {
            // treatment
        }
        dbg!(&data);
        Ok(())
    }
})
.await

Which wraps the variable in an immutable state.

Or by forcing the move of the boolean instead of its copy. This is done by wrapping the boolean into a non-copy structure.

The boolean can be recovered through the into() call

#[derive(Debug)]
struct Data;

let data = Data;

db.run(|trx, maybe_committed| {
    struct Wrapper(bool);
    impl From<Wrapper> for bool {
        fn from(value: Wrapper) -> Self {
            value.0
        }
    }

    let maybe_committed = Wrapper(maybe_committed);

    async {
        if maybe_committed.into() {
            // treatment
        }
        dbg!(&data);
        Ok(())
    }
})
.await

This way the data keeps its type.

As I prefer the second solution, but because the boilerplate is a bit heavy. I would like to modify the boolean type of mayby_committed into a wrapped boolean implementing Into.

This way the API becomes:

db.run(|trx, maybe_committed| async {
    if maybe_committed.into() {
        // treatment
    }
    dbg!(&data);
    Ok(())
})
.await

Leaving the closure non-capturing.

[codecov-commenter]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (a19d710) 82.37% compared to head (5554f18) 83.04%.

Files	Patch %	Lines
foundationdb/src/database.rs	0.00%	6 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #113      +/-   ##
==========================================
+ Coverage   82.37%   83.04%   +0.66%     
==========================================
  Files          23       23              
  Lines        4909     4914       +5     
==========================================
+ Hits         4044     4081      +37     
+ Misses        865      833      -32     

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