Function ensureHighlightedDiffLoaded

src/ui/diff/useHighlightedDiff.ts:104–136

Start one shared highlight request unless the cache or an in-flight promise already has it.

(
  file: DiffFile,
  theme: AppTheme,
  cacheKey = buildCacheKey(theme, file),
)

/** Start one shared highlight request unless the cache or an in-flight promise already has it. */
function ensureHighlightedDiffLoaded(
  file: DiffFile,
  theme: AppTheme,
  cacheKey = buildCacheKey(theme, file),
) {
  const cached = SHARED_HIGHLIGHTED_DIFF_CACHE.get(cacheKey);
  if (cached) {
    return Promise.resolve(cached);
  }

  const existing = SHARED_HIGHLIGHT_PROMISES.get(cacheKey);
  if (existing) {
    return existing;
  }

  let pending: Promise<HighlightedDiffCode>;
  pending = loadHighlightedDiff(file, theme)
    .then((nextHighlighted) => {
      commitHighlightResult(cacheKey, pending, nextHighlighted);
      return nextHighlighted;
    })
    .catch(() => {
      const fallback = {
        deletionLines: [],
        additionLines: [],
      } satisfies HighlightedDiffCode;
      commitHighlightResult(cacheKey, pending, fallback);
      return fallback;
    });

  SHARED_HIGHLIGHT_PROMISES.set(cacheKey, pending);
  return pending;
}

/** Queue syntax highlighting for one file without mounting its diff rows first. */
export function prefetchHighlightedDiff({ file, theme }: { file: DiffFile; theme: AppTheme }) {