**As** an OpenProject user
**I want to** make sure that changing start/finish dates of a Begin of the insertionprecedingEnd of the insertion Begin of the deletion preceedingEnd of the deletion work package won't change the start/finish dates of following work packages _only_ if the changes violate the relationship
**so that** dates of following work packages are not automatically changed when I don't expect them to

### Current behaviour

Today, when **adding** a follows/precedes relationship, assuming A is Begin of the insertionprecedingEnd of the insertion Begin of the deletion preceedingEnd of the deletion and B is following:

When B has no dates:

* If A Begin of the deletion onlyEnd of the deletion has a Begin of the insertionfinishEnd of the insertion Begin of the deletion startEnd of the deletion date and B has no dates, **B will derive its start date from the Begin of the insertionfinishEnd of the insertion Begin of the deletion startEnd of the deletion date of Begin of the insertionBEnd of the insertion Begin of the deletion AEnd of the deletion (n+1 day)** Begin of the insertion
* This is true regardless of A having a start date or notEnd of the insertion
* If A only has a Begin of the insertionstartEnd of the insertion Begin of the deletion finishEnd of the deletion date and B has no dates, **B will derive its start date from the Begin of the insertionstartEnd of the insertion Begin of the deletion finishEnd of the deletion date of Begin of the insertionAEnd of the insertion Begin of the deletion BEnd of the deletion (n+1 day)** Begin of the deletion
* This is also true if A has both start and finish datesEnd of the deletion

When A has no dates but B has start/finish dates:

* If A has no dates but B has a start date _or_ finish date _or_ both, A will not derive any dates (empty start/finish).

When both A and B both have dates:

* If the start Begin of the insertion_and_End of the insertion Begin of the deletion _or_End of the deletion finish date of B Begin of the insertionareEnd of the insertion Begin of the deletion isEnd of the deletion later than the start Begin of the insertion_and_End of the insertion Begin of the deletion _or_End of the deletion finish date of A, the dates of both work packages will be conserved.
* If the start _or_ finish date of B is Begin of the insertionearlierEnd of the insertion Begin of the deletion laterEnd of the deletion than the start _or_ finish date of A, **B will derive its start date based on the Begin of the insertionsoonest startEnd of the insertion Begin of the deletion finishEnd of the deletion date of Begin of the insertionA (finish date of A + 1,End of the insertion Begin of the deletion A,End of the deletion or start date Begin of the insertionof A + 1End of the insertion if finish date Begin of the insertionisEnd of the insertion Begin of the deletion doesEnd of the deletion not Begin of the insertionset)**.End of the insertion Begin of the deletion exist**.End of the deletion

Until here, things make sense. However, the problematic behaviour is this:

When A has dates (start, finish or both):

* When B only has a finish date (anytime in the future), when simply _moving A_, **B will derive its start date based on the finish date of A, or start date if finish date does not exist**.
* When B has no dates at all, simple _moving A_, **B will derive its start date based on the finish date of A, or start date if finish date does not exist**.

Here's a screencap of this behaviour:

<img class="op-uc-image op-uc-image_inline" src="/api/v3/attachments/38584/content">

### **Acceptance criteria**

To make this behaviour more consistent, and in line with <mention class="mention" data-id="44053" data-type="work_package" data-text="#44053">#44053</mention> (where moving a following/preceding will conserve dates and not moving related work packages around unless that relationship is violated):

* When A has dates (start, finish or both) and B either does not have dates:
* Moving A has no effect on the dates of B
* When A has dates (start, finish or both) and B has a finish date:
* Moving A will only mean a start date will be derived for B if it is moved _after_ this finish date (thereby Begin of the insertionpreventing a violation ofEnd of the insertion Begin of the deletion violatingEnd of the deletion the follows relationship) Begin of the deletion
*End of the deletion