General ItemMeta fixes

paper-api/src/main/java/org/bukkit/FireworkEffect.java

@@ -322,9 +322,7 @@ public final class FireworkEffect implements ConfigurationSerializable {
     private String string = null;
 
     FireworkEffect(boolean flicker, boolean trail, @NotNull ImmutableList<Color> colors, @NotNull ImmutableList<Color> fadeColors, @NotNull Type type) {
-        if (colors.isEmpty()) {
-            throw new IllegalStateException("Cannot make FireworkEffect without any color");
-        }
+        // Paper - can have empty colors
         this.flicker = flicker;
         this.trail = trail;
         this.colors = colors;

paper-api/src/main/java/org/bukkit/inventory/meta/CompassMeta.java

@@ -28,7 +28,8 @@ public interface CompassMeta extends ItemMeta {
     /**
      * Sets the location this lodestone compass will point to.
      *
-     * @param lodestone new location or null to clear
+     * @param lodestone new location or null to clear the targeted location
+     * @see #clearLodestone() to reset the compass to a normal compass
      */
     void setLodestone(@Nullable Location lodestone);
 
@@ -49,9 +50,25 @@ public interface CompassMeta extends ItemMeta {
      * location.
      *
      * @param tracked new tracked status
+     * @see #clearLodestone() to reset the compass to a normal compass
      */
     void setLodestoneTracked(boolean tracked);
 
+    // Paper start - Add more lodestone compass methods
+    /**
+     * Checks if this compass is considered a lodestone compass.
+     * @see #hasLodestone() to check if a position is being tracked
+     * @see #isLodestoneTracked() to check if it verifies the position is a lodestone
+     */
+    boolean isLodestoneCompass();
+
+    /**
+     * Reset this compass to a normal compass, removing any tracked
+     * location.
+     */
+    void clearLodestone();
+    // Paper end - Add more lodestone compass methods
+
     @Override
     CompassMeta clone();
 }

paper-api/src/main/java/org/bukkit/inventory/meta/Damageable.java

@@ -9,14 +9,17 @@ import org.jetbrains.annotations.Nullable;
 public interface Damageable extends ItemMeta {
 
     /**
-     * Checks to see if this item has damage
+     * Checks to see if this item has damage greater than 0.
      *
-     * @return true if this has damage
+     * @return true if this has damage > 0
      */
     boolean hasDamage();
 
     /**
      * Gets the damage
+     * <p>
+     * Call {@link #hasDamageValue()} to be sure
+     * a damage value is set.
      *
      * @return the damage
      */
@@ -26,9 +29,27 @@ public interface Damageable extends ItemMeta {
      * Sets the damage
      *
      * @param damage item damage
+     * @see #resetDamage() to reset and clear the damage data component
      */
     void setDamage(int damage);
 
+    // Paper start
+    /**
+     * Checks if any damage value, including 0,
+     * is set on this meta.
+     *
+     * @return true if any value is set
+     */
+    boolean hasDamageValue();
+
+    /**
+     * Clears the damage component from the meta. Differs
+     * from {@code setDamage(0)} in that it removes the component
+     * instead of adding the component with a value of 0.
+     */
+    void resetDamage();
+    // Paper end
+
     /**
      * Checks to see if this item has a maximum amount of damage.
      *

paper-api/src/main/java/org/bukkit/inventory/meta/ItemMeta.java

@@ -386,7 +386,7 @@ public interface ItemMeta extends Cloneable, ConfigurationSerializable, Persiste
     /**
      * Sets the enchantable. Higher values allow higher enchantments.
      *
-     * @param enchantable enchantable value
+     * @param enchantable enchantable value, must be positive
      */
     void setEnchantable(@Nullable Integer enchantable);
 
@@ -930,8 +930,9 @@ public interface ItemMeta extends Cloneable, ConfigurationSerializable, Persiste
 
     /**
      * Set all {@link Attribute}s and their {@link AttributeModifier}s.
-     * To clear all currently set Attributes and AttributeModifiers use
-     * null or an empty Multimap.
+     * To clear all custom attribute modifiers, use {@code null}. To set
+     * no modifiers (which will override the default modifiers), use an
+     * empty map.
      * If not null nor empty, this will filter all entries that are not-null
      * and add them to the ItemStack.
      *