Function writeTransientVersionsInPlace

packages/bumpy/src/core/prerelease.ts:201–232

(
  plan: ReleasePlan,
  packages: Map<string, WorkspacePackage>,
)

 * combination of packages installed from the dist-tag resolves to the
 * coherent set it was published with.
 */
export async function writeTransientVersionsInPlace(
  plan: ReleasePlan,
  packages: Map<string, WorkspacePackage>,
): Promise<() => Promise<void>> {
  const releaseMap = new Map(plan.releases.map((r) => [r.name, r]));
  const originals = new Map<string, string>();

  for (const release of plan.releases) {
    const pkg = packages.get(release.name);
    if (!pkg) continue;
    const pkgJsonPath = resolve(pkg.dir, 'package.json');
    originals.set(pkgJsonPath, await readText(pkgJsonPath));

    await updateJsonFields(pkgJsonPath, { version: release.newVersion });

    // Exact-pin in-cycle deps (dev deps excluded — not installed by consumers)
    for (const depField of ['dependencies', 'peerDependencies', 'optionalDependencies'] as const) {
      const deps = pkg[depField];
      for (const depName of Object.keys(deps)) {
        const depRelease = releaseMap.get(depName);
        if (!depRelease) continue;
        await updateJsonNestedField(pkgJsonPath, depField, depName, depRelease.newVersion);
      }
    }
  }

  return async () => {
    for (const [path, content] of originals) {
      await writeText(path, content);
    }
  };
}

/**