Function findFileByName

findFileByName(
    bucket: Bucket,
    fileName: string,
    bucketDisplayName?: string,
): Promise<FileVersion>
Look up the most-recent visible (action: 'upload') version of a file by its exact name. Throws if no upload version exists (hidden / deleted / never existed). Used by copy, delete, and retention to resolve a file name to a fileId before operating on it.

Consistency assumption: B2's listFileNames is read-after-write consistent for a recently-uploaded file in the same region. The simulator returns uploads immediately; production B2 in practice does the same, but a caller that chains "upload then operate on the same name" across two action steps is relying on observed behavior rather than a documented SLA.
Parameters
- bucket: Bucket
  The bucket to search.
- fileName: string
  Exact file name (path) to look up.
- OptionalbucketDisplayName: string
  Optional label for the error message; defaults to bucket.name. Used when looking up in a source bucket distinct from the action's destination bucket (cross-bucket copy).
Returns Promise<FileVersion>
- Defined in b2-action/src/client.ts:103