azblob: StorageError might be empty for the current implement UnmarshalXML in the azurite environment.

[Leavrth]

Bug Report

• import path of package in question: import github.com/Azure/azure-sdk-for-go/sdk/storage/azblob
• SDK version master
• output of go version

go version
go version go1.16.7 darwin/amd64

• What happened?
  This is my code, and the azurite is running.

import (
	"context"
	"fmt"

	"github.com/Azure/azure-sdk-for-go/sdk/storage/azblob"
)
func main() {
	connStr := "DefaultEndpointsProtocol=http;AccountName=devstoreaccount1;AccountKey=Eby8vdM02xNOcqFlqUwJPLlmEtlCDXJ1OUzFT50uSRZ6IFsuFq2UVErCz4I6tq/K1SZFPTOtr/KBHBeksoGMGw==;BlobEndpoint=http://127.0.0.1:10000/devstoreaccount1;"
	service, err := azblob.NewServiceClientFromConnectionString(connStr, nil)
	if err != nil {
		fmt.Printf("err1 %s", err.Error())
		return
	}
	ctx := context.Background()
	client := service.NewContainerClient("test254").NewBlockBlobClient("tt2")
	_, err = client.Download(ctx, nil)
	if err != nil {
		fmt.Printf("err %s\n", err.Error())
		return
	}
	return
}

In fact, container test254 is not exsit in the Azurite. So we will see the error print in the terminal.
But terminal show this,

err ===== RESPONSE ERROR (ErrorCode=
  ) =====
Description=
, Details: 
   : 
  

• What did you expect or want to happen?
  Instead, it should show this,

err ===== RESPONSE ERROR (ErrorCode=ContainerNotFound) =====
Description=The specified container does not exist.
RequestId:e10eeea8-73cf-4ec9-b717-ea1f4ee47a8b
Time:2021-12-09T05:49:23.887Z, Details: 
   : 

I insert fmt.Printf to print the info into these positions:

azure-sdk-for-go/sdk/azcore/runtime/response.go

Lines 73 to 92 in d528b56

	// UnmarshalAsXML calls xml.Unmarshal() to unmarshal the received payload into the value pointed to by v.
	func UnmarshalAsXML(resp *http.Response, v interface{}) error {
	payload, err := Payload(resp)
	if err != nil {
	return err
	}
	// TODO: verify early exit is correct
	if len(payload) == 0 {
	return nil
	}
	err = removeBOM(resp)
	if err != nil {
	return err
	}
	err = xml.Unmarshal(payload, v)
	if err != nil {
	err = fmt.Errorf("unmarshalling type %T: %s", v, err)
	}
	return err
	}

print the payload:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Error>
  <Code>ContainerNotFound</Code>
  <Message>The specified container does not exist.
RequestId:e10eeea8-73cf-4ec9-b717-ea1f4ee47a8b
Time:2021-12-09T05:49:23.887Z</Message>
</Error>

azure-sdk-for-go/sdk/storage/azblob/zc_storage_error.go

Lines 187 to 210 in 7551544

	// UnmarshalXML performs custom unmarshalling of XML-formatted Azure storage request errors.
	//nolint
	func (e *StorageError) UnmarshalXML(d *xml.Decoder, start xml.StartElement) (err error) {
	tokName := ""
	var t xml.Token
	for t, err = d.Token(); err == nil; t, err = d.Token() {
	switch tt := t.(type) {
	case xml.StartElement:
	tokName = tt.Name.Local
	case xml.CharData:
	switch tokName {
	case "Message":
	e.description = string(tt)
	default:
	if e.details == nil {
	e.details = map[string]string{}
	}
	e.details[tokName] = string(tt)
	}
	}
	}
	return nil
	}

insert after L195 to print token name fmt.Printf("token name is %s\n", tokName)
insert after L199 to print description fmt.Printf("description is %s\n", e.description)
insert after L204 to print detail fmt.Printf("detail[%s]=%s\n", tokName, string(tt))

detail[]=
  
token name is Code
detail[Code]=ContainerNotFound
detail[Code]=
  
token name is Message
description is The specified container does not exist.
RequestId:e8be3a84-f877-4b62-a7aa-7aaa8d44ccb4
Time:2021-12-09T06:19:16.483Z
description is 

I found each value are overwrite with empty value.

after insert case xml.EndElement: to reset tokenName, everything seems ok.

// UnmarshalXML performs custom unmarshalling of XML-formatted Azure storage request errors.
//nolint
func (e *StorageError) UnmarshalXML(d *xml.Decoder, start xml.StartElement) (err error) {
	tokName := ""
	var t xml.Token
	for t, err = d.Token(); err == nil; t, err = d.Token() {
		switch tt := t.(type) {
		case xml.StartElement:
			tokName = tt.Name.Local
		case xml.CharData:
			switch tokName {
			case "Message":
				e.description = string(tt)
			default:
				if e.details == nil {
					e.details = map[string]string{}
				}
				e.details[tokName] = string(tt)
			}
		case xml.EndElement:
			tokName = ""
		}
	}

	return nil
}

• How can we reproduce it?
  run the Azurite, and run my code above.
• Anything we should know about your environment.

[mohsha-msft]

Hey @Leavrth ,

Thanks for reporting the issue. @johnstairs has fixed the issue and I've merged it in dev-azblob branch.
Can you please try go get github.com/Azure/azure-sdk-for-go/sdk/storage/azblob@dev-azblob.

Please reach out if the issue persists.

[mohsha-msft]

Once we do the next release of azblob, we'll include this change and close this issue.

[mohsha-msft]

Fixed in sdk/storage/azblob/v0.3.0