Mocking free functions from modules in another file

[asomers]

Mocking free functions from modules in another file

[asomers]

No, you can't do that. Module declarations don't get expanded when proc macros get evaluated, so as your code is written automock can't see the contents of some_module at all. It thinks its an empty module. Instead, try like this:

main.rs:

#![feature(proc_macro_hygiene)]
#[cfg(test)]
use mockall::predicate::eq;

pub mod some_module;
use some_module::free_function;

fn my_func() {
    free_function(7);
}

fn main() {
}

#[test]
fn some_test() {
    let context = some_module::free_function_context();
    context.expect().times(1).with(eq(7)).returning(|_x| ());
    my_func();
}

some_module.rs:

use cfg_if::cfg_if;
#[cfg(test)]
use mockall::automock;

#[cfg_attr(test, automock)]
pub mod inner {
    pub fn free_function(_arg: i32) {}
}

cfg_if! {
    if #[cfg(test)] {
        pub use mock_inner::*;
    } else {
        pub use inner::*;
    }
}

I'll see if I can add a compiler error for using automock that way.

[lromeo]

Great, thank you. That works as is, but extending a little further I'm stuck on the following scoping issue. I can open as a separate issue if that would be better.

some_module.rs:

use cfg_if::cfg_if;
#[cfg(test)]
use mockall::automock;

pub struct SomeStruct {}

#[cfg_attr(test, automock)]
pub mod inner {
    use super::SomeStruct;
    pub fn free_function(_arg: SomeStruct) {}
}

cfg_if! {
    if #[cfg(test)] {
        pub use mock_inner::*;
    } else {
        pub use inner::*;
    }
}

main.rs:

#![feature(proc_macro_hygiene)]
#[cfg(test)]
use mockall::predicate::*;

pub mod some_module;
use some_module::*;

fn my_func() {
    let s = some_module::SomeStruct {};
    some_module::free_function(s);
}

fn main() {
}

#[test]
fn some_test() {
    let context = some_module::free_function_context();
    context.expect().times(1).with(always()).returning(|_x| ());
    my_func();
}

gives:

error[E0412]: cannot find type `SomeStruct` in this scope
  --> src/some_module.rs:10:32
   |
10 |     pub fn free_function(_arg: SomeStruct) {}
   |                                ^^^^^^^^^^ not found in this scope

...

It works if some_module.rs is updated to only uses absolute paths:

#[cfg_attr(test, automock)]
pub mod inner {
    pub fn free_function(_arg: crate::some_module::SomeStruct) {}
}

[asomers]

Yes, that's different. Please open a separate issue for it, and I'll suggest some other workarounds.