Bad Access: Nil Dereference Case Occurs in log function of sugar.go

[Osiris1975]

Hi,

I'm currently writing a CRUD microservice that uses zap logger. When I create an object via my POST endpoint, I have no problems. Here's my object model:

type Field struct {
	Id            int64     `json:"id" gorm:"primary_key"`
	PartnerId     int       `json:"partner_id" gorm:"not_null"`
	QualifiedName string    `json:"qualified_name" binding:"required" gorm:"unique; not_null"`
	Description   string    `json:"description"`
	DataType      DataType  `json:"data_type" binding:"required" validate:"oneof=0 1" enums:"string,int"`
	CreatedAt     time.Time `json:"created_at"`
	CreatedBy     int64     `json:"created_by"`
	UpdatedAt     time.Time `json:"updated_at"`
	UpdatedBy     int64     `json:"updated_by"`
}

As you can see from the tags, QualifiedName is required and unique. So if I try to recreate the same object, I should get an error indicating that an object with that same qualified name already exists.

Here's the code that handles creating the object:

func handleCreateField(c *gin.Context, svc field.RegistrationService) {
	user := auth.GetUser(c)

	var f field.Field
	var err error

	//FIXME: Currently trying to create an object that already exists leads to 'bad access: nil dereference'somewhere inside of a ShouldBondJSON goroutine
	if err = c.ShouldBindJSON(&f); err != nil {
		_ = c.Error(err)
		return
	}

	if user != nil {
		f.PartnerId = user.PartnerID
		f.CreatedBy = user.ID
		f.UpdatedBy = f.CreatedBy
	}

	if err = svc.Create(&f); err != nil {
		_ = c.Error(err)
		return
	}
	c.JSON(http.StatusOK, f)
}

If I step through the debugger, the error occurs somewhere in the call to c.ShouldBindJSON(&f). Eventually, stepping though leads to the "bad access: nil dereference" message triggered in this part of sugar.go.

func (s *SugaredLogger) log(lvl zapcore.Level, template string, fmtArgs []interface{}, context []interface{}) {
	// If logging at this level is completely disabled, skip the overhead of
	// string formatting.
	if lvl < DPanicLevel && !s.base.Core().Enabled(lvl) {
		return
	}

At this point, the request never returns a response, and continuing from the breakpoint I placed on if lvl < DPanicLevel && !s.base.Core().Enabled(lvl) just returns to this breakpoint, so it appears to be stuck in a goroutine or loop that won't terminate on its own. I would note that that value of s here is nil which is probably why I'm encountering this. What I can't figure out is why s is nil.

Any help or suggestions appreciated. Note that I'm also cross-posting on StackOverflow.

[prashantv]

Hi @Osiris1975, your issue has a combination of gin, gorm, and zap, and it's hard to tease apart what exactly is the issue. The code samples you provided have no reference to a logger or a log call, and so it's not clear how the log call even happens.

It's possible that your configuration to create the logger is incorrect (#777) or your logger is not created at all, so check those first.

If you continue to see this issue, please provide a minimal reproduction without any other libraries, so we can investigate the issue further.