Allow conversion from Report to Error

[TimDiekmann]

🌟 What is the purpose of this PR?

It's currently hard to deal with Report when an Error is required. This PR adds conversions from Report to Error.

🔗 Related links

• resolves Make Report compatible with std::error::Error based types #1746

🔍 What does this change?

• Add Report::into_error to convert impl Error
• Add Report::as_error to return &impl Error
• Add From implementation of Report for Box<dyn Error> (+ Send and/or Sync)

📜 Does this require a change to the docs?

The changelog was changed to reflect these changes

🛡 What tests cover this?

Three new tests were added:

• A UI test to make sure, that into_report cannot be called on Result<T, Report<C>>
• Two tests to check the new methods/trait implementation by converting a Report to Error and ensure, that the provided values are still accessible

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[codecov]

Codecov Report

Merging #1749 (07968da) into main (1e14659) will increase coverage by 0.03%.
The diff coverage is 70.00%.

@@            Coverage Diff             @@
##             main    #1749      +/-   ##
==========================================
+ Coverage   55.42%   55.46%   +0.03%     
==========================================
  Files         223      224       +1     
  Lines       15096    15136      +40     
  Branches      378      378              
==========================================
+ Hits         8367     8395      +28     
- Misses       6724     6736      +12     
  Partials        5        5              

Flag	Coverage Δ
backend-integration-tests	2.87% <ø> (ø)
error-stack	90.32% <70.00%> (-0.55%)	⬇️
unit-tests	1.66% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/libs/error-stack/src/lib.rs	38.46% <ø> (ø)
packages/libs/error-stack/src/report.rs	85.22% <62.50%> (-3.59%)	⬇️
packages/libs/error-stack/src/error.rs	81.25% <81.25%> (ø)

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[indietyp]

Out of curiosity, any reason for choosing for_each over for frame in self.frames()?

[TimDiekmann]

No specific reason. I used it here as it's only one line vs three lines.

[indietyp]

I love how CLion always automatically adds this line...

[indietyp]

Looks good to me, just some minor non-blocking comments. I already noted this over private DMs, but with this change

#[test]
fn as_error_nest() {
    let report = create_report();
    let base = report.into_error();
    let report = Report::new(base);

    println!("{report:?}");
}

is possible. I think that is ok, as it does not break formatting and has quite the high barrier for creating it.

[TimDiekmann]

Thanks, @indietyp!
Yes, that's possible but this was also possible before by creating a newtype for Report and implementing the required traits on that. The barrier, however, to do this is high enough and one cannot accidentally call into_report().