Function lineDiff

scripts/check-route-trees.ts:78–91

(committed: string, regenerated: string)

/** The lines each side has and the other does not — enough to name the route
 *  that drifted, without pulling in a diff library for a CI guard. */
const lineDiff = (committed: string, regenerated: string): string => {
  const committedLines = new Set(committed.split("\n"));
  const regeneratedLines = new Set(regenerated.split("\n"));
  const missing = [...regeneratedLines].filter((line) => !committedLines.has(line));
  const extra = [...committedLines].filter((line) => !regeneratedLines.has(line));
  const show = (label: string, lines: readonly string[]) =>
    lines.length === 0
      ? []
      : [`    ${label}:`, ...lines.slice(0, 20).map((line) => `      ${line}`)];
  return [
    ...show("in the regenerated tree but NOT committed (missing routes)", missing),
    ...show("committed but NOT regenerated (stale routes)", extra),
  ].join("\n");
};

type Failure = { readonly tree: string; readonly detail: string };
const failures: Failure[] = [];