Assign updated bitemporal times to the receiver after update/destroy

[wata727]

See also #117
Closes #100

We originally planned to assign all attributes to the receiver after update/destroy, but ran into some issues. See #117 for the motivation of this PR.

This PR changes the update/delete operation to only assign valid time/transaction time instead of all attributes. This eliminates the inconsistency described in #117, but the receiver does not always match the actual history when a callback is applied.

Below is an example:

class Employee
  before_create :set_current_time

  def set_current_time
    self.current_time = TIme.current
  end
end

employee = nil

Timecop.freeze("2020/09/01") {
  valid_datetime = "2020/06/01"
  ActiveRecord::Bitemporal.valid_at("2020/06/01") {
    employee = Employee.create(name: "hoge")
  }
}

Timecop.freeze("2020/09/02") {
  ActiveRecord::Bitemporal.valid_at("2020/07/01") {
    pp employee.valid_from.to_time         # => 2020-06-01 09:00:00 +0900
    pp employee.transaction_from.to_time   # => 2020-09-01 09:00:00 +0900

    employee.update!(name: "foo")

    # Updated valid_from/transaction_from
    pp employee.valid_from.to_time         # => 2020-07-01 09:00:00 +0900
    pp employee.transaction_from.to_time   # => 2020-09-02 09:00:00 +0900

    # Refer to current time before update
    pp employee.current_time.to_time       # => 2020-09-01 09:00:00 +0900
    employee.reload
    pp employee.current_time.to_time       # => 2020-09-02 09:00:00 +0900
  }
}

All attribute assignments were required to prevent this issue.

Since we don't assign all attributes, the only reliable receiver attributes are the following. Do not trust that any other value is equal to the latest history.

• swapped_id
• swapped_id_previously_was
• valid_from
• valid_to
• transaction_from
• transaction_to
• saved_changes

[osyo-manga]

OK, Thanks :)

[Dooor]

👍

[motsat]

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