Function resolveLibFilename

packages/vite/src/node/build.ts:996–1027

(
  libOptions: LibraryOptions,
  format: ModuleFormat,
  entryName: string,
  root: string,
  extension?: JsExt,
  packageCache?: PackageCache,
)

}

export function resolveLibFilename(
  libOptions: LibraryOptions,
  format: ModuleFormat,
  entryName: string,
  root: string,
  extension?: JsExt,
  packageCache?: PackageCache,
): string {
  if (typeof libOptions.fileName === 'function') {
    return libOptions.fileName(format, entryName)
  }

  const packageJson = findNearestMainPackageData(root, packageCache)?.data
  const name =
    libOptions.fileName ||
    (packageJson && typeof libOptions.entry === 'string'
      ? getPkgName(packageJson.name)
      : entryName)

  if (!name)
    throw new Error(
      'Name in package.json is required if option "build.lib.fileName" is not provided.',
    )

  extension ??= resolveOutputJsExtension(format, packageJson?.type)

  if (format === 'cjs' || format === 'es') {
    return `${name}.${extension}`
  }

  return `${name}.${format}.${extension}`
}

export function resolveBuildOutputs(
  outputs: OutputOptions | OutputOptions[] | undefined,