[DRAFT]: feat: normalize effective setter methods

src/main/java/org/openrewrite/java/migrate/lombok/LombokUtils.java

@@ -24,8 +24,10 @@
 import org.openrewrite.java.tree.Expression;
 import org.openrewrite.java.tree.J;
 import org.openrewrite.java.tree.JavaType;
+import org.openrewrite.java.tree.Statement;
 
 import java.util.List;
+import java.util.stream.Collectors;
 
 import static lombok.AccessLevel.*;
 import static org.openrewrite.java.tree.J.Modifier.Type.*;
@@ -156,6 +158,42 @@ private static boolean hasMatchingSetterMethodName(J.MethodDeclaration method, S
         return method.getSimpleName().equals("set" + StringUtils.capitalize(simpleName));
     }
 
+    public static boolean isEffectivelySetter(J.MethodDeclaration method) {
+        boolean isVoid = "void".equals(method.getType().toString());
+        List<Statement> actualParameters = method.getParameters().stream()
+                .filter(s -> !(s instanceof J.Empty))
+                .collect(Collectors.toList());
+        boolean oneParam = actualParameters.size() == 1;
+        if (!isVoid || !oneParam)
+            return false;
+
+        J.VariableDeclarations variableDeclarations = (J.VariableDeclarations) actualParameters.get(0);
+        J.VariableDeclarations.NamedVariable param = variableDeclarations.getVariables().get(0);
+        String paramName = param.getName().toString();
+
+        boolean singularStatement = method.getBody() != null //abstract methods can be null
+                && method.getBody().getStatements().size() == 1 &&
+                method.getBody().getStatements().get(0) instanceof J.Assignment;
+
+        if (!singularStatement) {
+            return false;
+        }
+        J.Assignment assignment = (J.Assignment) method.getBody().getStatements().get(0);
+
+        if (assignment.getVariable() instanceof J.FieldAccess || assignment.getVariable() instanceof J.Identifier) {
+            JavaType fieldType = assignment.getVariable().getType();
+            // assigned value is exactly the parameter
+            return assignment.getAssignment().toString().equals(paramName) &&
+                            param.getType() != null &&
+                            param.getType().equals(fieldType);  // type of parameter and field have to match
+        }
+        return false;
+    }
+
+    public static String deriveSetterMethodName(JavaType.Variable fieldType) {
+        return "set" + StringUtils.capitalize(fieldType.getName());
+    }
+
     static AccessLevel getAccessLevel(J.MethodDeclaration methodDeclaration) {
         if (methodDeclaration.hasModifier(Public)) {
             return PUBLIC;

src/main/java/org/openrewrite/java/migrate/lombok/NormalizeSetter.java

@@ -0,0 +1,181 @@
+/*
+ * Copyright 2024 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.java.migrate.lombok;
+
+import lombok.EqualsAndHashCode;
+import lombok.Value;
+import org.jspecify.annotations.Nullable;
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.ScanningRecipe;
+import org.openrewrite.Tree;
+import org.openrewrite.TreeVisitor;
+import org.openrewrite.java.ChangeMethodName;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaType;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+@Value
+@EqualsAndHashCode(callSuper = false)
+public class NormalizeSetter extends ScanningRecipe<NormalizeSetter.MethodAcc> {
+
+    private final static String DO_NOT_RENAME = "DO_NOT_RENAME";
+
+    @Override
+    public String getDisplayName() {
+        return "Rename setter methods to fit lombok";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Rename methods that are effectively setter to the name lombok would give them.\n" +
+                "Limitations:\n" +
+                " - If two methods in a class are effectively the same setter then one's name will be corrected and the others name will be left as it is.\n" +
+                " - If the correct name for a method is already taken by another method then the name will not be corrected.\n" +
+                " - Method name swaps or circular renaming within a class cannot be performed because the names block each other. " +
+                "E.g. `int getFoo() { return ba; } int getBa() { return foo; }` stays as it is.";
+    }
+
+    public static class MethodAcc {
+        List<RenameRecord> renameRecords = new ArrayList<>();
+    }
+
+    @Value
+    private static class RenameRecord {
+        String pathToClass_;
+        String methodName_;
+        String parameterType_;
+        String newMethodName_;
+    }
+
+    @Override
+    public MethodAcc getInitialValue(ExecutionContext ctx) {
+        return new MethodAcc();
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getScanner(MethodAcc acc) {
+        return new JavaIsoVisitor<ExecutionContext>() {
+
+            @Override
+            public J.ClassDeclaration visitClassDeclaration(J.ClassDeclaration classDecl, ExecutionContext ctx) {
+
+                List<String> doNotRename = classDecl.getBody().getStatements().stream()
+                        .filter(s -> s instanceof J.MethodDeclaration)
+                        .map(s -> (J.MethodDeclaration) s)
+                        .map(J.MethodDeclaration::getSimpleName)
+                        .collect(Collectors.toList());
+
+                getCursor().putMessage(DO_NOT_RENAME, doNotRename);
+
+                super.visitClassDeclaration(classDecl, ctx);
+
+                return classDecl;
+            }
+
+            @Override
+            public J.MethodDeclaration visitMethodDeclaration(J.MethodDeclaration method, ExecutionContext ctx) {
+                assert method.getMethodType() != null;
+
+                if (!LombokUtils.isEffectivelySetter(method)) {
+                    return method;
+                }
+
+                // return early if the method overrides another
+                // if the project defined both the original and the overridden method,
+                // then the renaming of the "original" in the base class will cover the override
+                if (method.getLeadingAnnotations().stream().anyMatch(a -> "Override".equals(a.getSimpleName()))) {
+                    return method;
+                }
+
+                JavaType.Variable fieldType = extractVariable(method);
+
+                String expectedMethodName = LombokUtils.deriveSetterMethodName(fieldType);
+                String parameterType = fieldType.getType().toString();
+                String actualMethodName = method.getSimpleName();
+
+                // If method already has the name it should have, then nothing to be done
+                if (expectedMethodName.equals(actualMethodName)) {
+                    return method;
+                }
+
+                // If the desired method name is already taken by an existing method, the current method cannot be renamed
+                List<String> doNotRename = getCursor().getNearestMessage(DO_NOT_RENAME);
+                assert doNotRename != null;
+                if (doNotRename.contains(expectedMethodName)) {
+                    return method;
+                }
+                //WON'T DO: there is a rare edge case, that is not addressed yet.
+                // If `getFoo()` returns `ba` and `getBa()` returns `foo` then neither will be renamed.
+                // This could be fixed by compiling a list of planned changes and doing a soundness check (and not renaming sequentially, or rather introducing temporary method names)
+                // At this point I don't think it's worth the effort.
+
+
+                String pathToClass = method.getMethodType().getDeclaringType().getFullyQualifiedName().replace('$', '.');
+                //todo write separate recipe for merging effective setters
+                acc.renameRecords.add(
+                        new RenameRecord(
+                                pathToClass,
+                                actualMethodName,
+                                parameterType,
+                                expectedMethodName
+                        )
+                );
+                doNotRename.remove(actualMethodName);//actual method name becomes available again
+                doNotRename.add(expectedMethodName);//expected method name now blocked
+                return method;
+            }
+
+            private JavaType.@Nullable Variable extractVariable(J.MethodDeclaration method) {
+                J.Assignment assignment_ = (J.Assignment) method.getBody().getStatements().get(0);
+
+                JavaType.Variable fieldType;
+                if (assignment_.getVariable() instanceof J.FieldAccess) {
+                    J.FieldAccess fieldAccess = (J.FieldAccess) assignment_.getVariable();
+                    fieldType = fieldAccess.getName().getFieldType();
+                } else if (assignment_.getVariable() instanceof J.Identifier) {
+                    J.Identifier fieldAccess = (J.Identifier) assignment_.getVariable();
+                    fieldType = fieldAccess.getFieldType();
+                } else {
+                    //only those types above are possible, see LombokUtils::isEffectivelySetter
+                    throw new IllegalStateException("Unexpected type for returned variable");
+                }
+                return fieldType;
+            }
+        };
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor(MethodAcc acc) {
+
+        return new TreeVisitor<Tree, ExecutionContext>() {
+
+            @Override
+            public @Nullable Tree visit(@Nullable Tree tree, ExecutionContext ctx) {
+
+                for (RenameRecord rr : acc.renameRecords) {
+                    String methodPattern = String.format("%s %s(%s)", rr.pathToClass_, rr.methodName_, rr.parameterType_);
+                    tree = new ChangeMethodName(methodPattern, rr.newMethodName_, true, null)
+                            .getVisitor().visit(tree, ctx);
+                }
+                return tree;
+            }
+        };
+    }
+}