Simply put, the Ender Dragon is entirely immune to melee damage, making the fight fairly awkward

Steps to Reproduce

• Enter the end in Creative or Survival
• Wait for the Dragon to land on the center perch
• Attempt to hit it with any melee weapon

Expected Outcome

Dragon takes damage

What actually happens

The dragon doesn't even trigger the "hit" sound, implying the player's hits don't even register. Though, arrows work flawlessly

Other notes

It should be noted that this bug has been in effect since 1.7, when the dragon was made immune to thrown tridents when perched. Perhaps a thrown trident mistakingly is registered as melee damage rather than projectile?