How to handle lifetimes within mock! block?

[mknet]

Hello everybody,

could you give me a hint on how to deal with lifetimes within the mock! macro block?

I want to do something like this:

use mockall::*;
use mockall::predicate::*;
use std::fmt;

#[cfg(test)]
mod tests {
    use super::*;

    mock! {
        MyStruct {}

        impl fmt::Debug for MyStruct { 
            fn fmt(&self, f: &mut fmt::Formatter<'a>) -> fmt::Result {
                f.write_str("MyStruct")
            }
        }
    }

    #[test]
    fn test_clone() {
        let mut mock1 = MockMyStruct::new();
        mock1.expect_fmt()
            .returning(|f| f.write_str("MyMock"));

        assert_eq!("MyMock", format!("{:?}", mock1));
    }
}

and I get a result like:

error[E0261]: use of undeclared lifetime name `'a`
  --> src/kapitel_5_5_2_3_externe_traits.rs:13:50
   |
13 |             fn fmt(&self, f: &mut fmt::Formatter<'a>) -> fmt::Result {
   |                                                  ^^ undeclared lifetime
...
17 |     }
   |      - lifetime `'a` is missing in item created through this procedural macro
   |
   = note: for more information on higher-ranked polymorphism, visit https://doc.rust-lang.org/nomicon/hrtb.html
help: consider making the bound lifetime-generic with a new `'a` lifetime
   |
9  |     for<'a> mock! {
   |     ^^^^^^^

But the suggested for<'a> mock is not of course working.

I'm looking forward to any hint.

Thanks and take care
Marcel

[asomers]

LOL, what timing! The easiest course of action for you would be to upgrade Mockall to the latest version in git. As of yesterday, it will automatically generate a Debug impl.
But if you don't want to do that, then write the function signature like this. I think all three of these forms will work:

• pub fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
• pub fn fmt<'a>(&self, f: &mut Formatter<'a>) -> Result<(), Error>;
• pub fn fmt(&self, f: &mut Formatter -> Result<(), Error>;

[mknet]

Of course! Well, I guess it was too late, yesterday.

I missed the missing lifetime after the function name...

fn fmt<'a>(&self, f: &mut fmt::Formatter<'a>) -> fmt::Result works for me

[asomers]

(also, you get to serve as Mockall's Discussions guinea pig. Let's see if Discussions are a better way to ask for help than Issues).

[mknet]

Gotcha