(&azcore.ResponseError{}).Error() panics

[jim-minter]

Bug Report

• import path of package in question: "github.com/Azure/azure-sdk-for-go/sdk/azcore"
• SDK version: v1.8.0
• output of go version: go version go1.21.1 linux/amd64

The expression (&azcore.ResponseError{}).Error() panics because the implementation of Error() requires multiple internal fields to be set.

The minimum instantiation of azcore.ResponseError that doesn't panic when Error() is called is something like:

(&azcore.ResponseError{
	RawResponse: &http.Response{
		Request: &http.Request{
			URL: &url.URL{},
		},
		Body: io.NopCloser(bytes.NewReader(nil)),
	},
}).Error()

This isn't something that we see is causing a production problem (although perhaps there is a minor robustness issue in the highly improbable production case that any of these fields is not set).

But, it's something that trips us up from time to time in a unit test context - when unit testing some other behavior, it's easy to inadvertently instantiate a ResponseError that will then cause a panic when Error() is called.

If only to simplify unit testing, it would be neat if (*azcore.ResponseError) Error() did not panic on a zero value &azcore.ResponseError{}.

[jhendrixMSFT]

Fix will go out in azcore@v1.9.0 in November.