Function detect_named_arg_context

src/completion/named_args.rs:103–151

Detect whether the cursor is inside a function/method call and extract the context needed for named-argument completion. Returns `None` if the cursor is not at an eligible position (e.g. after `$`, `->`, `::`, or inside a string/comment).

(content: &str, position: Position)

/// Returns `None` if the cursor is not at an eligible position (e.g. after
/// `$`, `->`, `::`, or inside a string/comment).
pub fn detect_named_arg_context(content: &str, position: Position) -> Option<NamedArgContext> {
    let chars: Vec<char> = content.chars().collect();
    let cursor = position_to_char_offset(&chars, position)?;

    // ── Check eligibility at cursor ─────────────────────────────────
    // Walk backward from cursor through identifier chars to find the
    // start of the current "word".
    let mut word_start = cursor;
    while word_start > 0
        && (chars[word_start - 1].is_alphanumeric() || chars[word_start - 1] == '_')
    {
        word_start -= 1;
    }

    // If preceded by `$`, this is a variable — not a named arg.
    if word_start > 0 && chars[word_start - 1] == '$' {
        return None;
    }

    // If preceded by `->` or `::`, member completion handles this.
    if word_start >= 2 && chars[word_start - 2] == '-' && chars[word_start - 1] == '>' {
        return None;
    }
    if word_start >= 2 && chars[word_start - 2] == ':' && chars[word_start - 1] == ':' {
        return None;
    }

    let prefix: String = chars[word_start..cursor].iter().collect();

    // ── Find enclosing open paren ───────────────────────────────────
    let open_paren = find_enclosing_open_paren(&chars, word_start)?;

    // ── Extract call expression before `(` ──────────────────────────
    let call_expr = extract_call_expression(&chars, open_paren)?;
    if call_expr.is_empty() {
        return None;
    }

    // ── Parse arguments between `(` and cursor ──────────────────────
    let args_text: String = chars[open_paren + 1..word_start].iter().collect();
    let (existing_named, positional_count) = parse_existing_args(&args_text);

    Some(NamedArgContext {
        call_expression: call_expr,
        existing_named_args: existing_named,
        positional_count,
        prefix,
    })
}

// Re-exported from `crate::util` for backward compatibility with
// existing import paths.