A unit charges over one friendly tray. He would not be able to have space between the enemy unit and the friendly tray without squaring up, but yes after it.

Is it considered a completed charge or a failed one?

It fails. Squaring up is not part of movement; it happens after movement. If you can't fit in the space, you can't complete your move, so you collide with your ally.

Budgernaut is clearing up questions on fire tonite!

just to feel part of it ill just say that i agree