The unlink() method bypasses the event triggering mechanism when the via is not null

[terranc]

The unlink() method bypasses the event triggering mechanism when the via is not null. It is not explained in the document, and I think this is not in line with my expectations. After all, it is not the unlinkAll() solution implemented.

version：2.0.49.3

public function unlink($name, $model, $delete = false)
    {
        /* @var $relation ActiveQueryInterface|ActiveQuery */
        $relation = $this->getRelation($name);

        if ($relation->via !== null) {
            if (is_array($relation->via)) {
                /* @var $viaRelation ActiveQuery */
                list($viaName, $viaRelation) = $relation->via;
                $viaClass = $viaRelation->modelClass;
                unset($this->_related[$viaName]);
            } else {
                $viaRelation = $relation->via;
                $viaTable = reset($relation->via->from);
            }
            $columns = [];
            foreach ($viaRelation->link as $a => $b) {
                $columns[$a] = $this->$b;
            }
            foreach ($relation->link as $a => $b) {
                $columns[$b] = $model->$a;
            }
            $nulls = [];
            foreach (array_keys($columns) as $a) {
                $nulls[$a] = null;
            }
            if (property_exists($viaRelation, 'on') && $viaRelation->on !== null) {
                $columns = ['and', $columns, $viaRelation->on];
            }
            if (is_array($relation->via)) {
                /* @var $viaClass ActiveRecordInterface */
                if ($delete) {
                    $viaClass::deleteAll($columns);
                } else {
                    $viaClass::updateAll($nulls, $columns);
                }
            } else {
                /* @var $viaTable string */
                /* @var $command Command */
                $command = static::getDb()->createCommand();
                if ($delete) {
                    $command->delete($viaTable, $columns)->execute();
                } else {
                    $command->update($viaTable, $nulls, $columns)->execute();
                }
            }
        } else {
            $p1 = $model->isPrimaryKey(array_keys($relation->link));
            $p2 = static::isPrimaryKey(array_values($relation->link));
            if ($p2) {
                if ($delete) {
                    $model->delete();
                } else {
                    foreach ($relation->link as $a => $b) {
                        $model->$a = null;
                    }
                    $model->save(false);
                }
            } elseif ($p1) {
                foreach ($relation->link as $a => $b) {
                    if (is_array($this->$b)) { // relation via array valued attribute
                        if (($key = array_search($model->$a, $this->$b, false)) !== false) {
                            $values = $this->$b;
                            unset($values[$key]);
                            $this->$b = array_values($values);
                        }
                    } else {
                        $this->$b = null;
                    }
                }
                $delete ? $this->delete() : $this->save(false);
            } else {
                throw new InvalidCallException('Unable to unlink models: the link does not involve any primary key.');
            }
        }

        if (!$relation->multiple) {
            unset($this->_related[$name]);
        } elseif (isset($this->_related[$name])) {
            /* @var $b ActiveRecordInterface */
            foreach ($this->_related[$name] as $a => $b) {
                if ($model->getPrimaryKey() === $b->getPrimaryKey()) {
                    unset($this->_related[$name][$a]);
                }
            }
        }
    }