When looking at When does a readied action trigger on "when the enemy moves"? it occurred to me that I may not understand Booming Blade as well as I thought I did.
Here is my point of confusion: if an enemy is 5 ft away from you when you cast Booming Blade, you do not move closer, and you do not have a reach weapon in hand, does the spell fail or can you make the melee attack anyway? To put it another way, if you are out of movement and you don't have a reach weapon, does Booming Blade's effective range drop to Touch?
I think part of my confusion is that Booming Blade is not worded like most attack cantrips.
[...] Range: 5ft [...] As part of the action used to cast this spell, you must make a successful melee attack with a weapon against one creature, otherwise the spell fails [...]
It's not a melee spell attack, like thorn whip, so I would assume that the attack here is held to all the standard restrictions that apply to a melee attack with a weapon, namely that you are attacking "a target within 5 feet of you". (Player's Handbook, pg. 146)
By contrast, I always thought that ranges indicated the maximum distance away a target could be. In that case, wouldn't an enemy that is 5ft away be at the range of Booming Blade (5ft) but too far away to hit with a non-reach melee weapon?
Can you successfully cast Booming Blade from 5ft away without moving and without a reach weapon, or no?