Q:

Oathbow conditions with Arcane Archer archetype's arcane shots

The Oathbow magic item says 

When you make a ranged Attack roll with this weapon against your sworn
  enemy, you have advantage on the roll. In addition, your target gains
  no benefit from cover, other than total cover, and you suffer no
  disadvantage due to long range. If the Attack hits, your sworn enemy
  takes an extra 3d6 piercing damage.

But one of the UA fighter archetypes, Arcane Archer (coming in the Xanatha's Guide next month, but previewed in Unearthed Arcana), has the ability to imbue their arrows with magic and two of them seems like it might conflict with the oathbow's trigger condition.

Piercing Arrow. You use transmutation magic to give   your arrow an
  ethereal quality. When you use this option, you don’t make an attack
  roll for the attack. Instead, the arrow fires forward in    a line that
  is 1 foot wide and 30 feet long, before disappearing. The arrow passes
  harmlessly through objects, ignoring cover. Each creature in that line
  must make a Dexterity saving throw. On a failed save, a target takes
  damage as if it were hit by the arrow, plus an extra 1d6 piercing
  damage. On    a successful save, a target takes half as much damage.
Seeking   Arrow. Using divination magic, you grant your
  arrow the ability to  seek    out your target, allowing the arrow to  curve
  and twist its path in search  of  its prey. When    you use this option,
  you don’t make an attack roll for the attack. Instead,
  choose    one creature you have seen in the past minute. The arrow    flies
  toward that creature, moving  around  corners if necessary and ignoring
  three-quarters    cover and half cover. If the target is  within the
  weapon’s range and there  is a path large enough for the arrow
  to    travel  to  the target, the target  must make a Dexterity saving
  throw.    On a failed save, it takes damage as if it  were hit
  by    the arrow, plus an extra 1d6 force damage, and you learn the
  target’s  current location. On a successful save, the target takes half
  as    much damage, and you don’t learn its location.

So how does this work with RAW? I know some situations override things going both ways in favor of exploitation and prevention.
Does the class skill let you bypass the attack roll while getting the oathbow's power buff or do you not get the buff?

A:

You don't get the buff, because the very first part of Oathbow reads:

When you make a ranged Attack roll

And with these spells, you don't make a ranged Attack roll. So nothing happens with the Oathbow.

