Add helper methods for creating and finding method and field nodes

src/main/java/net/minecraftforge/coremod/api/ASMAPI.java

@@ -20,6 +20,7 @@
 import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.lang.reflect.Modifier;
+import java.util.ArrayList;
 import java.util.ListIterator;
 import java.util.Objects;
 import java.util.Optional;
@@ -29,8 +30,210 @@
  * Helper methods for working with ASM.
  */
 public class ASMAPI {
+    /**
+     * Creates a new empty {@link MethodNode}.
+     *
+     * @return The created method node
+     *
+     * @see MethodNode#MethodNode(int)
+     */
     public static MethodNode getMethodNode() {
-        return new MethodNode(Opcodes.ASM9);
+        var method = new MethodNode(Opcodes.ASM9);
+
+        // ASM usually creates an empty list for null exceptions on the other constructors
+        // let's do this as well, just to make sure we don't run into problems later.
+        method.exceptions = new ArrayList<>();
+
+        return method;
+    }
+
+    /**
+     * Creates a new empty {@link MethodNode} with the given access codes, name and descriptor.
+     *
+     * @param access     The access codes
+     * @param name       The method name
+     * @param descriptor The method descriptor
+     * @return The created method node
+     *
+     * @see MethodNode#MethodNode(int, int, String, String, String, String[])
+     */
+    public static MethodNode getMethodNode(int access, String name, String descriptor) {
+        return new MethodNode(Opcodes.ASM9, access, name, descriptor, null, null);
+    }
+
+    /**
+     * Creates a new empty {@link MethodNode} with the given access codes, name, descriptor, and signature.
+     *
+     * @param access     The access codes
+     * @param name       The method name
+     * @param descriptor The method descriptor
+     * @param signature  The method signature
+     * @return The created method node
+     *
+     * @see MethodNode#MethodNode(int, int, String, String, String, String[])
+     */
+    public static MethodNode getMethodNode(int access, String name, String descriptor, @Nullable String signature) {
+        return new MethodNode(Opcodes.ASM9, access, name, descriptor, signature, null);
+    }
+
+    /**
+     * Creates a new empty {@link MethodNode} with the given access codes, name, descriptor, signature, and exceptions.
+     *
+     * @param access     The access codes
+     * @param name       The method name
+     * @param descriptor The method descriptor
+     * @param signature  The method signature
+     * @param exceptions The internal names of the method's exceptions
+     * @return The created method node
+     *
+     * @see MethodNode#MethodNode(int, int, String, String, String, String[])
+     */
+    public static MethodNode getMethodNode(int access, String name, String descriptor, @Nullable String signature, @Nullable String[] exceptions) {
+        return new MethodNode(Opcodes.ASM9, access, name, descriptor, signature, exceptions);
+    }
+
+    /**
+     * Creates a new empty {@link FieldNode} with the given access codes, name, and descriptor.
+     *
+     * @param access     The access codes
+     * @param name       The field name
+     * @param descriptor The field descriptor
+     * @return The created field node
+     *
+     * @see FieldNode#FieldNode(int, int, String, String, String, Object)
+     */
+    public static FieldNode getFieldNode(int access, String name, String descriptor) {
+        return new FieldNode(Opcodes.ASM9, access, name, descriptor, null, null);
+    }
+
+    /**
+     * Creates a new empty {@link FieldNode} with the given access codes, name, descriptor, and signature.
+     *
+     * @param access     The access codes
+     * @param name       The field name
+     * @param descriptor The field descriptor
+     * @param signature  The field signature
+     * @return The created field node
+     *
+     * @see FieldNode#FieldNode(int, int, String, String, String, Object)
+     */
+    public static FieldNode getFieldNode(int access, String name, String descriptor, @Nullable String signature) {
+        return new FieldNode(Opcodes.ASM9, access, name, descriptor, signature, null);
+    }
+
+    /**
+     * Creates a new empty {@link FieldNode} with the given access codes, name, descriptor, signature, and initial
+     * object value.
+     *
+     * @param access     The access codes
+     * @param name       The field name
+     * @param descriptor The field descriptor
+     * @param signature  The field signature
+     * @param value      The initial value of the field
+     * @return The created field node
+     *
+     * @see FieldNode#FieldNode(int, int, String, String, String, Object)
+     */
+    public static FieldNode getFieldNode(int access, String name, String descriptor, @Nullable String signature, String value) {
+        return new FieldNode(Opcodes.ASM9, access, name, descriptor, signature, value);
+    }
+
+    /**
+     * Creates a new empty {@link FieldNode} with the given access codes, name, descriptor, signature, and initial
+     * number value.
+     *
+     * @param access     The access codes
+     * @param name       The field name
+     * @param descriptor The field descriptor
+     * @param signature  The field signature
+     * @param value      The initial value of the field
+     * @param valueType  The number type of the initial value
+     * @return The created field node
+     *
+     * @see FieldNode#FieldNode(int, int, String, String, String, Object)
+     */
+    public static FieldNode getFieldNode(int access, String name, String descriptor, @Nullable String signature, Number value, NumberType valueType) {
+        return new FieldNode(Opcodes.ASM9, access, name, descriptor, signature, castNumber(value, valueType));
+    }
+
+    /**
+     * Finds the first method node from the given class node that matches the given name and descriptor.
+     *
+     * @param clazz The class node to search
+     * @param name  The name of the desired method
+     * @param desc  The descriptor of the desired method
+     * @return The found method node or null if none matched
+     */
+    public static @Nullable MethodNode findMethodNode(ClassNode clazz, String name, String desc) {
+        return findMethodNode(clazz, name, desc, null, false);
+    }
+
+    /**
+     * Finds the first method node from the given class node that matches the given name, descriptor, and signature.
+     *
+     * @param clazz     The class node to search
+     * @param name      The name of the desired method
+     * @param desc      The descriptor of the desired method
+     * @param signature The signature of the desired method
+     * @return The found method node or null if none matched
+     *
+     * @apiNote This method will attempt to match the signature of the method, even if it is {@code null}. It may be
+     *     useful for that use case in particular. If you have no need to match the signature, consider using
+     *     {@link #findMethodNode(ClassNode, String, String)}
+     */
+    public static @Nullable MethodNode findMethodNode(ClassNode clazz, String name, String desc, @Nullable String signature) {
+        return findMethodNode(clazz, name, desc, signature, true);
+    }
+
+    private static @Nullable MethodNode findMethodNode(ClassNode clazz, String name, String desc, @Nullable String signature, boolean checkSignature) {
+        for (MethodNode method : clazz.methods) {
+            // we have to use Objects.equals here in case the found method has null attributes
+            if (Objects.equals(method.name, name) && Objects.equals(method.desc, desc) && (!checkSignature || Objects.equals(method.signature, signature))) {
+                return method;
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * Finds the first field node from the given class node that matches the given name and descriptor.
+     *
+     * @param clazz The class node to search
+     * @param name  The name of the desired field
+     * @param desc  The descriptor of the desired field
+     * @return The found field node or null if none matched
+     */
+    public static @Nullable FieldNode findFieldNode(ClassNode clazz, String name, String desc) {
+        return findFieldNode(clazz, name, desc, null, false);
+    }
+
+    /**
+     * Finds the first field node from the given class node that matches the given name, descriptor, and signature.
+     *
+     * @param clazz     The class node to search
+     * @param name      The name of the desired field
+     * @param desc      The descriptor of the desired field
+     * @param signature The signature of the desired field
+     * @return The found field node or null if none matched
+     *
+     * @apiNote This method will attempt to match the signature of the field, even if it is {@code null}. It may be
+     *     useful for that use case in particular. If you have no need to match the signature, consider using
+     *     {@link #findFieldNode(ClassNode, String, String)}
+     */
+    public static @Nullable FieldNode findFieldNode(ClassNode clazz, String name, String desc, @Nullable String signature) {
+        return findFieldNode(clazz, name, desc, signature, true);
+    }
+
+    private static @Nullable FieldNode findFieldNode(ClassNode clazz, String name, String desc, @Nullable String signature, boolean checkSignature) {
+        for (FieldNode field : clazz.fields) {
+            // we have to use Objects.equals here in case the found field has null attributes
+            if (Objects.equals(field.name, name) && Objects.equals(field.desc, desc) && (!checkSignature || Objects.equals(field.signature, signature))) {
+                return field;
+            }
+        }
+
+        return null;
     }
 
     /**