APIError.Error() doesn't unwrap error correctly

[leventov]

Environment details

• Package version: 2.14.0

Code: https://github.com/googleapis/gax-go/blob/dc6baf75c1a737233739630b5af6c9759f08abcd/v2/apierror/apierror.go#L202C1-L208C82

Error from POST https://generativelanguage.googleapis.com/v1beta/models/gemini-2.0-flash-exp:streamGenerateContent?%24alt=json%3Benum-encoding%3Dint

httpErr.Message is empty, but httpErr.Body is not empty and contains a JSON list with a single object which has "message" field.

[quartzmo]

@leventov Thank you for reporting this issue. Can you provide a log statement with the error, and the JSON? Any more info that you can provide will be helpful, thank you.

[leventov]

httpErr.Body was exactly this:

[ {
  "error" : {
    "code" : 403,
    "message" : "Method doesn't allow unregistered callers (callers without established identity). Please use API Key or other form of API consumer identity to call this API.",
    "status" : "PERMISSION_DENIED"
  }
} ]

Note slight variation from the shape reported in google-gemini/generative-ai-python#463, where it's an object on the top level with "error" field. But in my case, it is additional array wrapping on top.

[leventov]

Also FYI, the root cause of the error was that I didn't provide api key but because genai package uses its custom Transport to pass api key. Here's the workaround: https://discuss.ai.google.dev/t/gemini-flash-2-0-error-403-method-doesnt-allow-unregistered-callers/54123/5?u=roman_leventov. This itself is a "usability bug" on the part google's genai Go packages, as I explained in that thread. It's absolutely not clear from the genai package's API that if you provide your custom HTTPClient you bork authentication.

Regardless, I'm not sure the failure the failure of gax to propagate error message was due to that specific "software" nature of the bug.

[quartzmo]

1. Was the error above produced by https://github.com/google/generative-ai-go?
2. Can you supply a full repro example, with imports? Please do not omit any code. It is much easier for us to debug the problem with full information (except your actual API key, of course).

[leventov]

1. Yes
2. No, sorry, I moved over and don't want to spend hours on exact reproducible now. Why wouldn't you just add more resilency code to https://github.com/googleapis/gax-go/blob/dc6baf75c1a737233739630b5af6c9759f08abcd/v2/apierror/apierror.go#L202C1-L208C82, checking if httpErr.Message is empty, and if yes, trying to unwrap httpErr.Body in various ways, or even just use it verbatim (still would be better, despite the surrounding clutter, than leaving the user in the dark about the source of error).

[quartzmo]

Why wouldn't you just...

Did gax-go throw an error, or did it just return an error cleanly but with an empty message?

[leventov]

It returned error with 403 code but no message. All I'm asking for is for code to try harder to propagate the error up so that debugging is easier. Well, it wasn't also that hard for me, I had to debug the code and set the breakpoint at line 208 here to investigate, but it's not supposed to be required, right? And maybe in some other environments or cross-process proxying settings debugging might me much harder.

Edit: by "no message" I mean that the error message was "googleapi: Error 403: ".

[quartzmo]

I understand that you are only interested in getting the message. We are also interested in the root cause of the missing message, which is why I need to ask these questions.