codex/prs/bolinfest/study/PR-1387-study.md

DOs

• Use is_some/is_none: Prefer direct Option checks when the value isn’t used.

// Do
if event.response.is_some() {
    let _ = tx_event.send(Ok(ResponseEvent::Created)).await;
}

• Prefer unit variants: Use unit enum variants when they carry no data.

// Do
#[derive(Debug)]
pub enum ResponseEvent {
    Created,
    // ...
}

match evt {
    ResponseEvent::Created => { /* ... */ }
    _ => {}
}

• Borrow with Cow to avoid clones: Only allocate when you must change the data.

use std::borrow::Cow;

fn with_missing_calls<'a>(prompt: &'a Prompt, missing_calls: Vec<ResponseItem>) -> Cow<'a, Prompt> {
    if missing_calls.is_empty() {
        Cow::Borrowed(prompt)
    } else {
        Cow::Owned(Prompt {
            input: [missing_calls, prompt.input.clone()].concat(),
            ..prompt.clone()
        })
    }
}

// Usage
let prompt = with_missing_calls(prompt, missing_calls);
let mut stream = sess.client.clone().stream(&prompt).await?;

• Explain non-obvious transformations: Add a concise comment where behavior isn’t obvious.

// The Responses API rejects follow-ups until all prior call_ids have outputs.
// If the previous turn was interrupted, prepend synthetic "aborted" outputs
// so this turn won’t 400 on missing call_ids.
let prompt = with_missing_calls(prompt, missing_calls);

• Use struct update syntax: Keep reconstructed structs concise and correct.

// Do
let prompt = Prompt {
    input: [missing_calls, prompt.input.clone()].concat(),
    ..prompt.clone()
};

DON’Ts

• Don’t pattern-match just to test presence: Avoid if let Some(_) = ... when you don’t use the value.

// Don't
if let Some(_) = event.response { /* ... */ }

• Don’t define empty struct-like variants: Avoid Created {} when no fields exist.

// Don't
pub enum ResponseEvent {
    Created {},
}

• Don’t clone large structs unnecessarily: Avoid prompt.clone() unless you’re actually modifying it.

// Don't
let prompt = prompt.clone(); // unnecessary if unchanged

• Don’t rebuild every field manually: Prefer ..prompt.clone() over listing unchanged fields.

// Don't
let prompt = Prompt {
    input,
    prev_id: prompt.prev_id.clone(),
    user_instructions: prompt.user_instructions.clone(),
    store: prompt.store,
    extra_tools: prompt.extra_tools.clone(),
};

• Don’t leave rationale implicit: When rewriting inputs (e.g., injecting missing call outputs), document why to aid future maintenance.