Say person a asks person b where he is going. Person b replies "the shop" but has no intention of going to the shop and instead is planning a visit to a friend. However, on his way to see his friend he does indeed change his mind and go to the shop.
Did person b lie?
Tough one.
My first response was same as what I read on first couple pages of this thread: intent was there to deceive the person asking the question.
But from person a's perspective, it cannot be a lie. The question isn't framed in OP as "where are you planning on going?" It is where are you going? So, in reality in that moment, person b can't say with 100% certainty that they know the answer to that. They can pretend like they do by sharing what they are planning, but again, that's not the question being asked.
So, lied to themselves perhaps, but when they said the shop, they answered the question that was asked. If they went to the shop, then the truth was told, not a lie.
I somewhat question the "no intention" part as that seems deceptive to us looking at this. Like if I say I have no intention of, I dunno, eating a hamburger today. Even say that to myself, and I do, then okay I lied to myself. But if someone else is involved and I say to them I'll be eating a hamburger today, how would that person ever know it was a lie, unless I volunteer my thoughts? Even then, I'd think that person would see it as no big deal, or that from their perspective the truth was told.
Such that the follow up from person b in OP would be: I told you earlier I was going to the shop, but I didn't intend on going there and was planning on going to a friend's instead, but then I went to the shop. To which person a would say, as far as I'm concerned, you told me the truth, and your added layer of honesty just makes it more clear to me you are always truthful to me.