Content-Language metadata field in GCS object not allowing ISO-639-2 from API - google-cloud-storage

Question

While trying to update the Content-Language metadata field of an object to ISO-639-2 field from the UI works fine, when trying to do the same from http API, it fails with an invalid argument error. The official documentation page states that ISO-639-1 codes are supported (although the link goes to 639-2).
Any ideas on how to update the Content-Language via http/json for objects in ISO-639-2 ? Or it's possible the UI treats it differently?
Response from GetObject for an object with ISO-639-2 updated via ui
{
"kind": "storage#object",
"id": "XXXXXXXXX/textfile.txt/XXXXXXX",
"selfLink": ...,
"mediaLink": ...,
"name": "textfile.txt",
"bucket": "XXXXXX",
"generation": "XXXXXX",
"metageneration": "2",
"contentType": "text/plain; charset=utf-8",
"storageClass": "STANDARD",
"size": "29",
"md5Hash": "f510qpm7Jh30uKbBcN4e0A==",
**"contentLanguage": "ach",**
"crc32c": "4fnpOw==",
"etag": "COet043XpPcCEAI=",
"temporaryHold": false,
"eventBasedHold": false,
"timeCreated": "2022-04-21T07:56:14.769Z",
"updated": "2022-04-21T07:57:14.321Z",
"timeStorageClassUpdated": "2022-04-21T07:56:14.769Z",
"metadata": {
"gcsfuse_mtime": "2022-04-21T07:56:13.375009661Z"
}
}
Error when trying to set the same value as received in the above call via json
{
"error": {
"code": 400,
"message": "Invalid argument.",
"errors": [
{
"message": "Invalid argument.",
"domain": "global",
"reason": "invalid"
}
]
}
}

Answer 1

I reproduced your case, and it seems like you are right. Content-Language only allows ISO 639-1 language codes for the supported values of this metadata.
When Content-Language was set to “ach” in JSON POST API call it gave me errors “curl: (3) Failed to convert ach” to ACE; string contains a disallowed character” but when set to “en”/ “de”/ “aa” it works fine and gives a HTTP 200 response. I think the logic which works here, checks for ISO 639-1 format.
I have gone through the documentation, and it says clearly “Refer to ISO 639-1 language codes for the supported values of this metadata.” Maybe it routes to ISO 639-2 page, because it contains both ISO 639-1 and ISO 639-2 codes, out of which it mentions it only supports ISO 639-1 language codes. You can check out this documentation as well.
Raise a feature request here so that the Content-Language supports ISO 639-2 language code in API calls.