Replace typed_builder with bon

[jssblck]

Overview

Replaces typed_builder with bon.

Primarily this is because it's annoying to have to do this:

let org_id = Some(1234);
let locator = StrictLocator::builder()
    .fetcher(Fetcher::Git)
    .package("...")
    .revision("...");
let locator = match org_id {
    None => locator.build(),
    Some(org_id) => locator.org_id(org_id).build(),
};

With bon, we can do this instead:

let org_id = Some(1234);
let locator = StrictLocator::builder()
    .fetcher(Fetcher::Git)
    .package("...")
    .revision("...")
    .maybe_org_id(org_id)
    .build();

And we can still build when we know we have a field:

let locator = StrictLocator::builder()
    .fetcher(Fetcher::Git)
    .package("...")
    .revision("...")
    .org_id(1234)
    .build();

Bon also generally encourages cleaner patterns (e.g. by requiring Into implementations instead of custom setters), generates nicer error messages, and generates cleaner code.

Acceptance criteria

Existing tests pass (demonstrating that this isn't a breaking change) and new functionality exists.

Testing plan

Automated testing

Metrics

None

Risks

At worst this might be secretly breaking for some edge case type conversion, but that should be easy enough for callers to work around if that's the case.

References

None

Checklist

• I added tests for this PR's change (or explained in the PR description why tests don't make sense).

[Veetaha]

by requiring Into implementations instead of custom setters

I don't think it was one of the goals, rather it's a missing feature which could be worked around by falling back to creating a builder from a function.

Anyway, I'm going to add #[builder(with = closure)] syntax to define custom setters, and make it possible to add custom methods to the builder in the next release (elastio/bon#145).

[jssblck]

@Veetaha good to know, thanks for the comment!

Honestly I like the current approach anyway: I'm a big fan of type-driven design, so doing it the way we have to today in bon is a positive to me. But for sure, adding this as an option certainly seems to not be a bad thing.

[spatten]

This looks great to me. I like the new syntax and the new tests :)