When creating a Spell Scroll using the rules from XGtE (p.133), if the spell is a cantrip the scroll is cast as if the caster were first level. If a Warlock with, say, Agonizing Blast were to scribe a scroll of Eldritch Blast, and have it used by another Warlock with Repelling Blast, would either invocation take effect?
Effectively: Is an invocation a property of the spell when being cast, or of the Warlock casting it?
In your study of occult lore, you have unearthed eldritch invocations, fragments of forbidden knowledge that imbue you with an abiding magical ability.
Invocations are abilities granted to the caster themself and, being not part of the actual spell, cannot be scribed onto a scroll.
Put another, more mechanical, way: warlock invocations modify the effects of spells after casting. They don't modify the spell being cast.
For example agonizing blast says:
When you cast eldritch blast, add your Charisma modifier to the damage it deals on a hit.
and repelling blast says:
When you hit a creature with eldritch blast, you can push the creature up to 10 feet away from you in a straight line.
Note the effects of these invocations only take effect after a spell is cast. Scribing a scroll is not casting it in any way.
If a warlock cast eldritch blast from a scroll and had this (or any applicable) invocation, they would be able to enhance it like normal even though nothing was different about the scroll they cast from.
Warlock A (who has agonizing blast) scribes a scroll of eldritch blast. That scroll results in a completely normal 1st level scroll of eldritch blast (devoid of any invocation effects). When warlock B (who has repelling blast) casts the spell from the scroll, any invocations that are applicable (that Warlock B has) would apply to the casting. Casting from a scroll is still casting the spell and it is treated as if it was cast normally.
Invocations, narratively and mechanically are not part of the spell, they are part of the caster.
