fix: behavior when getting removed callback

[snackmgmg]

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?

Resolved the issue where Get() retrieves a callback that has been removed by Remove().
This was due to the search continuing even when a callback with v.removed: true was found, eventually reaching another callback of the same name with v.removed: false.

User Case Description

If a callback named cb1 is registered, it is expected that calling Get("cb1") after Remove("cb1") should return nil. However, a callback function registered as cb1 is being returned instead.

db, _ := gorm.Open(tests.DummyDialector{}, nil)
createCallback := db.Callback().Create()

_ = createCallback.Register("cb1", func(*gorm.DB){})
_ = createCallback.Remove("cb1")

cb := createCallback.Get("cb1") // not nil

[a631807682]

Obtaining key values based on order does not solve this problem, because the deleted element may be at the front or at the back.

Failed case

- err := createCallback.Register("plugin_1_fn1", c1)
+ err := createCallback.Before("*").Register("plugin_1_fn1", c1)

I don't know the history of this part of the code, and I don't understand why the deleted callback is not removed when compiling.

[jinzhu]

previously, the callbacks system allowed a new callback to overwrite a previously deleted one, which is no longer supported now~

[jinzhu]

maybe we can remove the callback from processor.callbacks when call the Remove method

[snackmgmg]

Thank you for your review. You are right, I overlooked that part.
Additionally, after reviewing your comments, I realized that the Remove() is not working properly either.
For instance, it seems that callbacks are not being removed in certain cases.

func TestRemoveNotWorking(t *testing.T) {
	db, _ := gorm.Open(nil, nil)
	rawCallback := db.Callback().Raw()

	rawCallback.Before("*").Register("cb1", func(*gorm.DB) { panic("Remove does not work") })
	rawCallback.Remove("cb1")

	db.Exec("SELECT 1") // panic
}

// In this case, it works correctly.
func TestRemoveWorking(t *testing.T) {
	db, _ := gorm.Open(nil, nil)
	rawCallback := db.Callback().Raw()

	rawCallback.Before("*").Register("cb1", func(*gorm.DB) { panic("Remove does not work") })
	rawCallback.Before("*").Remove("cb1")

	db.Exec("SELECT 1") // not panic
}

I think that adopting the method of removing callbacks that have been marked for removal is not only a solution for the Get() issue but also addresses the problem with Remove().
I will try this approach. Thank you!

[snackmgmg]

Sorry, I forgot to close this.