oxc-project/oxc · error

line break count must fit in u32

Error message

line break count must fit in u32

What it means

Assertion in the formatter's exact_line_breaks builder: the requested line-break count is accumulated into a u32 counter (with checked adds), so a count that does not fit in u32 cannot be represented and the builder panics up front rather than silently truncating verbatim blank-line output.

Source

Thrown at crates/oxc_formatter_core/src/write/builders.rs:88

/// For blank runs inside verbatim values (block scalars, block strings),
/// where the number of line breaks IS the value and must not be normalized.
/// From a mid-line position the first break ends the current line, leaving `count - 1` blank lines;
/// from the start of a line all `count` breaks become blank lines.
///
/// Unlike [hard_line_break]:
/// - the breaks always print, regardless of the current line or a preceding blank line
/// - consecutive calls accumulate, nothing is collapsed or capped
///
/// The blank lines themselves carry no indention;
/// the NEXT line starts at the current indention (same re-arming as [hard_line_break]).
///
/// # Panics
/// When `count == 0` or `count > u32::MAX`.
/// Both are unreachable from source-derived callers: a source of N bytes cannot hold more than N line breaks,
/// and sources are capped at `u32::MAX` by `oxc_span::Span`.
#[inline]
pub fn exact_line_breaks(count: usize) -> Line {
    let count = u32::try_from(count).expect("line break count must fit in u32");
    let count = std::num::NonZeroU32::new(count).expect("line break count must be >= 1");
    Line::new(LineMode::ExactLineBreaks(count))
}

/// A forced line break that starts the next line at the marked root indention (Prettier's `literalline`).
///
/// Unlike [hard_line_break]:
/// - pending whitespace on the current line materializes as-is (never dropped)
/// - the newline always prints, even on an empty line
/// - the next line starts at the [mark_as_root] indention (column 0 when unmarked)
///   instead of the current indention
///
/// Used for verbatim multi-line content whose line structure is built element by element (e.g. YAML block scalars).
/// For verbatim content held as ONE string,
/// a multiline [text] already prints its embedded newlines with these semantics.
///
/// Known divergence from Prettier:
/// a [hard_line_break] directly after a literal line is absorbed by

View on GitHub (pinned to 1f902a6962)

Solutions

1. Clamp or split the break count into batches that each fit in u32
2. Emit the blank lines via multiple exact_line_breaks calls instead of one huge count

When it happens

Trigger: Thrown at crates/oxc_formatter_core/src/write/builders.rs:75 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of oxc-project/oxc@1f902a6962 (2026-08-20). Data as JSON: /api/errors/8ccf1633623cae8a. Report an issue: GitHub.