Add @NotNull and @Nullable annotations to methods and parameters across modules

- Annotate `equals`, `toString`, and other critical methods with nullability annotations for improved clarity and static analysis.
- Adjust constructors and method signatures to explicitly define nullable parameters.
- Update imports where necessary to support new annotations.

Signed-off-by: Erik Pförtner <splatcrafter@splatgames.de>

Author: Splatcrafter

aether-datafixers-api/src/main/java/de/splatgames/aether/datafixers/api/DataVersion.java

@@ -27,6 +27,7 @@
 import de.splatgames.aether.datafixers.api.fix.DataFixer;
 import de.splatgames.aether.datafixers.api.schema.Schema;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.Objects;
 
@@ -171,7 +172,7 @@ public int compareTo(@NotNull final DataVersion o) {
      * @see #hashCode()
      */
     @Override
-    public boolean equals(final Object obj) {
+    public boolean equals(@Nullable final Object obj) {
         if (this == obj) {
             return true;
         }
@@ -222,6 +223,7 @@ public int hashCode() {
      * @return a string representation of this data version in the format {@code "DataVersion{version=N}"}
      */
     @Override
+    @NotNull
     public String toString() {
         return "DataVersion{" + "version=" + this.version + '}';
     }

aether-datafixers-api/src/main/java/de/splatgames/aether/datafixers/api/TypeReference.java

@@ -28,6 +28,7 @@
 import de.splatgames.aether.datafixers.api.type.Type;
 import de.splatgames.aether.datafixers.api.type.TypeRegistry;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 /**
  * A unique identifier for a data type in the data fixing system.
@@ -183,7 +184,7 @@ public int hashCode() {
      * @see #hashCode()
      */
     @Override
-    public boolean equals(final Object obj) {
+    public boolean equals(@Nullable final Object obj) {
         if (this == obj) {
             return true;
         }
@@ -217,6 +218,7 @@ public boolean equals(final Object obj) {
      * @see #getId()
      */
     @Override
+    @NotNull
     public String toString() {
         return "TypeReference{" + "id='" + this.id + '\'' + '}';
     }

aether-datafixers-api/src/main/java/de/splatgames/aether/datafixers/api/dynamic/TaggedDynamic.java

@@ -25,6 +25,7 @@
 import com.google.common.base.Preconditions;
 import de.splatgames.aether.datafixers.api.TypeReference;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 /**
  * A {@link Dynamic} value paired with a {@link TypeReference} identifier.
@@ -200,7 +201,7 @@ public Dynamic<?> value() {
      * @return {@code true} if this object is the same as the obj argument; {@code false} otherwise
      */
     @Override
-    public boolean equals(final Object obj) {
+    public boolean equals(@Nullable final Object obj) {
         if (this == obj) {
             return true;
         }
@@ -237,6 +238,7 @@ public int hashCode() {
      * @return a string representation of the object
      */
     @Override
+    @NotNull
     public String toString() {
         return "TaggedDynamic{" +
                 "type=" + this.type +

aether-datafixers-api/src/main/java/de/splatgames/aether/datafixers/api/exception/DataFixerException.java

@@ -155,6 +155,7 @@ public String getContext() {
      * @return the message with context, or just the message if no context
      */
     @Override
+    @NotNull
     public String toString() {
         final String base = getClass().getSimpleName() + ": " + getMessage();
         if (this.context != null) {

aether-datafixers-api/src/main/java/de/splatgames/aether/datafixers/api/fix/Fixes.java

@@ -147,6 +147,7 @@ public Optional<Typed<?>> rewrite(@NotNull final Type<?> type,
             }
 
             @Override
+            @NotNull
             public String toString() {
                 return name;
             }
@@ -210,6 +211,7 @@ public Optional<Typed<?>> rewrite(@NotNull final Type<?> inputType,
             }
 
             @Override
+            @NotNull
             public String toString() {
                 return name;
             }
@@ -309,6 +311,7 @@ public static <T, A> TypeRewriteRule addField(@NotNull final DynamicOps<T> ops,
             }
 
             @Override
+            @NotNull
             public String toString() {
                 return "addField(" + fieldName + ")";
             }
@@ -390,6 +393,7 @@ public static <T> TypeRewriteRule fixChoice(@NotNull final DynamicOps<T> ops,
             }
 
             @Override
+            @NotNull
             public String toString() {
                 return "fixChoice(" + tagField + ", " + fixByTag.keySet() + ")";
             }
@@ -447,6 +451,7 @@ public static <T> TypeRewriteRule renameChoice(@NotNull final DynamicOps<T> ops,
             }
 
             @Override
+            @NotNull
             public String toString() {
                 return "renameChoice(" + tagField + ": " + oldTag + " -> " + newTag + ")";
             }
@@ -520,6 +525,7 @@ public Optional<Typed<?>> rewrite(@NotNull final Type<?> type,
             }
 
             @Override
+            @NotNull
             public String toString() {
                 return name;
             }

aether-datafixers-api/src/main/java/de/splatgames/aether/datafixers/api/result/DataResult.java

@@ -778,7 +778,7 @@ public DataResult<A> promotePartial(@NotNull final Consumer<String> onError) {
          * @return {@code true} if the other object is a Success with an equal value
          */
         @Override
-        public boolean equals(final Object obj) {
+        public boolean equals(@Nullable final Object obj) {
             if (this == obj) {
                 return true;
             }
@@ -803,8 +803,8 @@ public int hashCode() {
          *
          * @return a string in the format "DataResult.Success[value]"
          */
-        @NotNull
         @Override
+        @NotNull
         public String toString() {
             return "DataResult.Success[" + this.value + "]";
         }
@@ -1150,7 +1150,7 @@ public DataResult<A> promotePartial(@NotNull final Consumer<String> onError) {
          * @return {@code true} if the other object is an Error with equal message and partial
          */
         @Override
-        public boolean equals(final Object obj) {
+        public boolean equals(@Nullable final Object obj) {
             if (this == obj) {
                 return true;
             }
@@ -1177,8 +1177,8 @@ public int hashCode() {
          *
          * @return a string in the format "DataResult.Error[message]" or "DataResult.Error[message, partial=value]"
          */
-        @NotNull
         @Override
+        @NotNull
         public String toString() {
             if (this.partial != null) {
                 return "DataResult.Error[" + this.message + ", partial=" + this.partial + "]";