⚡ Bolt: Remove intermediate allocations when joining strings

[madmax983]

💡 What: Replaced .collect::<Vec<_>>().join(...) with .fold(...) along with String::with_capacity to build strings directly. Additionally resolved a while_let_loop lint and map_unwrap_or lint in unrelated files.
🎯 Why: .collect::<Vec<_>>().join(...) allocates an intermediate vector before allocating the joined string, taking extra CPU cycles and memory. Doing it manually with .fold skips the intermediate vector entirely.
📊 Impact: Reduces heap allocs by 1 vector allocation for each call.
🔬 Measurement: Verified the code compiles, works correctly, and passes all tests without regressions via cargo check and cargo test.

---

PR created automatically by Jules for task 15264098696242478243 started by @madmax983

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.

[gemini-code-assist]

Code Review

This pull request optimizes string joining operations across several files (calibrate.rs, swebench.rs, and skills.rs) by replacing vector collection and joining with inline fold operations to avoid intermediate allocations. It also simplifies a socket read loop, improves error reporting in test timeouts, and refactors a split operation. The review feedback suggests replacing the complex inline fold operations with more readable and idiomatic iterator loops that preallocate exact capacities, avoiding branching and unnecessary reallocations.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.

[gemini-code-assist]

The inline fold with enumerate is hard to read and introduces a conditional check on every iteration. We can simplify this by precalculating the exact capacity and using a clean iterator pattern with next() and a simple loop. This is more idiomatic, highly readable, and avoids branching inside the loop.

    let total_len: usize = values.iter().map(|s| s.len()).sum();
    let cap = total_len + values.len().saturating_sub(1);
    let mut iter = values.into_iter();
    let Some(first) = iter.next() else {
        return String::new();
    };
    let mut acc = String::with_capacity(cap);
    acc.push_str(first);
    for s in iter {
        acc.push(',');
        acc.push_str(s);
    }
    acc

[gemini-code-assist]

The inline fold here is complex and hard to read. Since this is an error path, we can write a clean, explicit string builder block that preallocates the exact capacity and joins the strings using a simple loop. This significantly improves readability and maintainability.

            let total_len: usize = unknown.iter().map(|s| s.len()).sum();
            let cap = total_len + unknown.len().saturating_sub(1) * 2;
            let mut iter = unknown.into_iter();
            let mut joined = String::with_capacity(cap);
            if let Some(first) = iter.next() {
                joined.push_str(first);
                for s in iter {
                    joined.push_str(", ");
                    joined.push_str(s);
                }
            }
            return Err(Error::Config(crate::error::ConfigError::Invalid(format!(
                "--instance-ids references unknown id(s): {joined}"
            ))));

[gemini-code-assist]

Using fold(String::new(), ...) without preallocating causes multiple reallocations as the string grows. Since we already have out, we can preallocate the exact upper bound capacity using out.len() and join the words using a clean iterator loop. This is more performant and much easier to read.

    let mut iter = out.split_whitespace();
    let Some(first) = iter.next() else {
        return String::new();
    };
    let mut acc = String::with_capacity(out.len());
    acc.push_str(first);
    for s in iter {
        acc.push(' ');
        acc.push_str(s);
    }
    acc

[codecov]

Codecov Report

❌ Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.19%. Comparing base (9aa2ad9) to head (723f61c).

Files with missing lines	Patch %	Lines
src/stream/sweep_webhook.rs	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            trunk     #598      +/-   ##
==========================================
- Coverage   85.19%   85.19%   -0.01%     
==========================================
  Files         114      114              
  Lines       65408    65404       -4     
==========================================
- Hits        55725    55720       -5     
- Misses       9683     9684       +1     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.