Function resolve

packages/react/src/__tests__/exports.test.ts:523–603

* Resolve the given import or export source. If the source is a filepath, it * will attempt to resolve the module relative to the given filepath.

(
  source: string,
  filepath: string,
)

 * will attempt to resolve the module relative to the given filepath.
 */
function resolve(
  source: string,
  filepath: string,
): ResolveBareModule | ResolveRelativeModule | ResolveAbsoluteModule | ResolveError {
  if (source.startsWith('.')) {
    const directory = path.dirname(filepath)
    const extension = path.extname(source)
    if (extension === '' || !extensions.includes(extension)) {
      const candidate = extensions
        .flatMap(extension => {
          return [
            path.resolve(
              directory,
              path.format({
                name: source,
                ext: extension,
              }),
            ),
            path.resolve(
              directory,
              path.format({
                dir: source,
                name: 'index',
                ext: extension,
              }),
            ),
          ]
        })
        .find(candidate => {
          return existsSync(candidate)
        })
      if (candidate) {
        return {
          type: 'relative',
          value: candidate,
        }
      }

      return {
        type: 'error',
        error: new Error(`Unable to find file: ${source} from: ${filepath}`),
      }
    }

    const resolvedPath = path.resolve(directory, source)
    if (!existsSync(resolvedPath)) {
      return {
        type: 'error',
        error: new Error(`Unable to find file: ${source} from: ${filepath}`),
      }
    }
    return {
      type: 'relative',
      value: resolvedPath,
    }
  }

  if (source.startsWith('/')) {