chore: where possible replace async-trait with native async trait support in 1.75+

[39555]

As of Rust 1.75, the async_fn_in_trait feature has been merged (see: rust-lang/rust#115822), meaning the async-trait crate is now only required for dynamic dispatch (dyn Trait). Since brush doesn’t use dyn Command, I decided to try removing the dependency. The modules arithmetic.rs and interp.rs are most affected, as they use async recursion, which requires futures to be boxed. I’ve wrapped all recursive functions in async move { .. }.boxed().

[github-actions]

Performance Benchmark Report

Benchmark name	Baseline (μs)	Test/PR (μs)	Delta (μs)	Delta %
expand_one_string	3.33 μs	3.33 μs	-0.00 μs	⚪ Unchanged
instantiate_shell	60.20 μs	59.96 μs	-0.24 μs	⚪ Unchanged
instantiate_shell_with_init_scripts	29796.80 μs	29501.12 μs	-295.69 μs	⚪ Unchanged
parse_bash_completion	2725.56 μs	2713.36 μs	-12.20 μs	⚪ Unchanged
parse_sample_script	4.02 μs	4.03 μs	0.01 μs	⚪ Unchanged
run_echo_builtin_command	88.94 μs	90.27 μs	1.33 μs	⚪ Unchanged
run_one_builtin_command	107.75 μs	109.15 μs	1.40 μs	⚪ Unchanged
run_one_external_command	2047.21 μs	1967.89 μs	-79.32 μs	🟢 -3.87%
run_one_external_command_directly	1013.85 μs	1014.20 μs	0.35 μs	⚪ Unchanged

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
brush-core/src/builtins/alias.rs	🟠 66.67%	🟠 70.37%	🟢 3.7%
brush-core/src/builtins/break_.rs	🟢 77.78%	🟢 84.62%	🟢 6.84%
brush-core/src/builtins/builtin_.rs	🟢 94.12%	🟢 95%	🟢 0.88%
brush-core/src/builtins/cd.rs	🟠 75%	🟢 78.57%	🟢 3.57%
brush-core/src/builtins/command.rs	🟢 91.67%	🟢 91.95%	🟢 0.28%
brush-core/src/builtins/complete.rs	🔴 21.85%	🔴 22.11%	🟢 0.26%
brush-core/src/builtins/continue_.rs	🟢 81.82%	🟢 86.67%	🟢 4.85%
brush-core/src/builtins/declare.rs	🟢 81.64%	🟢 81.79%	🟢 0.15%
brush-core/src/builtins/dirs.rs	🟢 84.38%	🟢 85.71%	🟢 1.33%
brush-core/src/builtins/dot.rs	🟢 90%	🟢 91.67%	🟢 1.67%
brush-core/src/builtins/echo.rs	🟢 86.05%	🟢 86.96%	🟢 0.91%
brush-core/src/builtins/enable.rs	🟠 71.74%	🟠 73.47%	🟢 1.73%
brush-core/src/builtins/eval.rs	🟢 90.91%	🟢 92.86%	🟢 1.95%
brush-core/src/builtins/exec.rs	🟢 85.19%	🟢 86.67%	🟢 1.48%
brush-core/src/builtins/export.rs	🟠 72.55%	🟠 74.07%	🟢 1.52%
brush-core/src/builtins/getopts.rs	🟢 90.79%	🟢 91.14%	🟢 0.35%
brush-core/src/builtins/help.rs	🟢 89.02%	🟢 89.41%	🟢 0.39%
brush-core/src/builtins/jobs.rs	🔴 25.64%	🔴 30.95%	🟢 5.31%
brush-core/src/builtins/let_.rs	🟢 88.89%	🟢 90.48%	🟢 1.59%
brush-core/src/builtins/popd.rs	🟢 91.67%	🟢 93.33%	🟢 1.66%
brush-core/src/builtins/printf.rs	🟢 91.3%	🟢 91.84%	🟢 0.54%
brush-core/src/builtins/pushd.rs	🟢 88.89%	🟢 90.48%	🟢 1.59%
brush-core/src/builtins/pwd.rs	🟠 69.23%	🟢 80.95%	🟢 11.72%
brush-core/src/builtins/read.rs	🟠 64.33%	🟠 65%	🟢 0.67%
brush-core/src/builtins/return_.rs	🟠 75%	🟢 81.82%	🟢 6.82%
brush-core/src/builtins/set.rs	🟠 68.47%	🟠 69.3%	🟢 0.83%
brush-core/src/builtins/shift.rs	🟢 94.44%	🟢 95.24%	🟢 0.8%
brush-core/src/builtins/shopt.rs	🟠 69.05%	🟠 70.11%	🟢 1.06%
brush-core/src/builtins/test.rs	🟢 85%	🟢 86.96%	🟢 1.96%
brush-core/src/builtins/trap.rs	🟠 67.9%	🟠 69.05%	🟢 1.15%
brush-core/src/builtins/type_.rs	🟢 79.01%	🟢 79.76%	🟢 0.75%
brush-core/src/builtins/unalias.rs	🟢 85%	🟢 86.96%	🟢 1.96%
brush-core/src/builtins/unset.rs	🟢 80%	🟢 82.61%	🟢 2.61%
brush-core/src/builtins/wait.rs	🟠 65%	🟠 69.57%	🟢 4.57%
brush-core/src/interp.rs	🟢 90.21%	🟢 90.19%	🔴 -0.02%
brush-interactive/src/interactive_shell.rs	🟠 68.25%	🟠 71.43%	🟢 3.18%
brush-shell/src/brushctl.rs	🔴 17.14%	🔴 15.38%	🔴 -1.76%
brush-shell/src/shell_factory.rs	🔴 23.08%	🔴 34.78%	🟢 11.7%
Overall Coverage	🟢 72.24%	🟢 72.33%	🟢 0.09%

Minimum allowed coverage is 70%, this run produced 72.33%

[reubeno]

Thanks for looking at this.

Do you know if there's a way to keep the simpler return types (using the 'async' keyword's syntactic sugar)? At least for the simpler cases.

Also, for recursive cases, would be interesting to know if there are any crates with macros that are 1.75+ but "do the boxing for us" under the hood. This would also be mainly to keep the code slightly simpler to read/maintain.

[39555]

That's what async_trait or async_recursion do, but async_recursion does not work with an empty trait function body. I will revert the recursive functions since async_trait is really nice, and I forgot Pin<..> anyway. At least other traits without recursion would benefit from the native async though.

[reubeno]

That sounds like a better direction. Let's remove unnecessary #[async_trait::async_trait] attributes where it should now "just work natively". For other places where we'd have to make the code less readable, let's hold off for now.

[39555]

@reubeno done

[reubeno]

LGTM.

Thanks also for addressing some warnings along the way. I'll get this merged, but if you find additional warnings like these that aren't being caught by the GitHub PR workflows, then it would be interesting to figure out how we could tweak things to catch them in the future.