Background

The effects_changed advancement trigger should work after an effect is given to or taken from the player.

The bug

When using a player predicate in the advancement trigger to attempt to check if a certain effect is taken from the player, it is rather checked before the effect is taken away from them:

{
  "criteria": {
    "speed": {
      "trigger": "effects_changed",
      "conditions": {
        "player": [
          {
            "condition": "inverted",
            "term": {
              "condition": "entity_properties",
              "entity": "this",
              "predicate": {
                "effects": {
                  "speed": {}
                }
              }
            }
          }
        ]
      }
    }
  },
  "rewards": {
    "function": "game:effects_changed"
  }
}

How to reproduce

1. Create an advancement such as the one shown above to check for a certain effect taken from the player.
2. Create a reward function for the advancement:

   advancement revoke @s only game:give_speed
   say Hello!
   

3. Use a Potion of Swiftness or /effect give @s speed to get the Speed effect.
4. Use a Milk Bucket or /effect clear to clear the effect.
   → The advancement is not granted and the message is not displayed.

Data pack

An attached data pack is provided below for easier reproduction.