Function try_parse_partial_json

core/src/llm/structured.rs:494–586

Attempt to parse a potentially incomplete JSON string into the most complete valid partial object possible. Strategy: try parsing as-is first. If that fails, progressively close open braces/brackets and try again. This handles the common case where the LLM has output `{"name": "foo", "items": [1, 2` — we close it to get a partial.

(text: &str)

/// braces/brackets and try again. This handles the common case where the LLM
/// has output `{"name": "foo", "items": [1, 2` — we close it to get a partial.
fn try_parse_partial_json(text: &str) -> Option<Value> {
    let trimmed = text.trim();
    if trimmed.is_empty() {
        return None;
    }

    // Fast path: already valid
    if let Ok(v) = serde_json::from_str::<Value>(trimmed) {
        if v.is_object() || v.is_array() {
            return Some(v);
        }
    }

    // Count unclosed brackets/braces (respecting strings)
    let mut closers = Vec::new();
    let mut in_string = false;
    let mut escape_next = false;
    // Track if we're mid-value (after a colon or comma, before the value is complete)
    let mut last_significant: Option<u8> = None;

    for &b in trimmed.as_bytes() {
        if escape_next {
            escape_next = false;
            continue;
        }
        match b {
            b'\\' if in_string => {
                escape_next = true;
            }
            b'"' => {
                in_string = !in_string;
                if !in_string {
                    last_significant = Some(b'"');
                }
            }
            _ if in_string => {}
            b'{' => {
                closers.push(b'}');
                last_significant = Some(b'{');
            }
            b'[' => {
                closers.push(b']');
                last_significant = Some(b'[');
            }
            b'}' | b']' => {
                closers.pop();
                last_significant = Some(b);
            }
            b':' | b',' => {
                last_significant = Some(b);
            }
            b if !b.is_ascii_whitespace() => {
                last_significant = Some(b);
            }
            _ => {}
        }
    }