org.openrewrite.staticanalysis.RemoveUnusedPrivateMethods Maven / Gradle / Ivy

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/*
 * Copyright 2021 the original author or authors.
 * 
 * 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
 * 

 * https://www.apache.org/licenses/LICENSE-2.0
 * 
 * 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.staticanalysis;

import org.jspecify.annotations.Nullable;
import org.openrewrite.ExecutionContext;
import org.openrewrite.Preconditions;
import org.openrewrite.Recipe;
import org.openrewrite.TreeVisitor;
import org.openrewrite.java.JavaIsoVisitor;
import org.openrewrite.java.NoMissingTypes;
import org.openrewrite.java.RemoveUnusedImports;
import org.openrewrite.java.search.FindAnnotations;
import org.openrewrite.java.service.AnnotationService;
import org.openrewrite.java.tree.*;

import java.time.Duration;
import java.util.Collections;
import java.util.List;
import java.util.Set;

public class RemoveUnusedPrivateMethods extends Recipe {

    @Override
    public String getDisplayName() {
        return "Remove unused private methods";
    }

    @Override
    public String getDescription() {
        return "`private` methods that are never executed are dead code and should be removed.";
    }

    @Override
    public Set getTags() {
        return Collections.singleton("RSPEC-S1144");
    }

    @Override
    public Duration getEstimatedEffortPerOccurrence() {
        return Duration.ofMinutes(5);
    }

    @Override
    public TreeVisitor getVisitor() {
        return Preconditions.check(new NoMissingTypes(), new JavaIsoVisitor() {

            @Override
            public J.ClassDeclaration visitClassDeclaration(J.ClassDeclaration classDeclaration, ExecutionContext ctx) {
                if (unusedWarningsSuppressed(classDeclaration)) {
                    return classDeclaration;
                }
                return super.visitClassDeclaration(classDeclaration, ctx);
            }

            private boolean unusedWarningsSuppressed(J classDeclaration) {
                for (J.Annotation annotation : FindAnnotations.find(classDeclaration, "java.lang.SuppressWarnings")) {
                    List arguments = annotation.getArguments();
                    if (arguments != null) {
                        for (Expression argument : arguments) {
                            if (J.Literal.isLiteralValue(argument, "all") ||
                                J.Literal.isLiteralValue(argument, "unused")) {
                                return true;
                            }
                        }
                    }
                }
                return false;
            }

            @Override
            public  J.@Nullable MethodDeclaration visitMethodDeclaration(J.MethodDeclaration method,
                    ExecutionContext ctx) {
                J.MethodDeclaration m = super.visitMethodDeclaration(method, ctx);
                JavaType.Method methodType = method.getMethodType();
                if (methodType != null && methodType.hasFlags(Flag.Private) &&
                    !method.isConstructor() &&
                    service(AnnotationService.class).getAllAnnotations(getCursor()).isEmpty()) {

                    J.ClassDeclaration classDeclaration = getCursor().firstEnclosing(J.ClassDeclaration.class);
                    if (classDeclaration == null) {
                        return m;
                    }
                    if (TypeUtils.isAssignableTo("java.io.Serializable", classDeclaration.getType())) {
                        switch (m.getSimpleName()) {
                            case "readObject":
                            case "readObjectNoData":
                            case "readResolve":
                            case "writeObject":
                                return m;
                        }
                    }

                    JavaSourceFile cu = getCursor().firstEnclosingOrThrow(JavaSourceFile.class);
                    for (JavaType.Method usedMethodType : cu.getTypesInUse().getUsedMethods()) {
                        if (methodType.getName().equals(usedMethodType.getName()) && methodType.equals(usedMethodType)) {
                            return m;
                        }
                    }

                    for (JavaType javaType : cu.getTypesInUse().getTypesInUse()) {
                        if (TypeUtils.isOfClassType(javaType, "org.junit.jupiter.params.provider.MethodSource")) {
                            return m;
                        }
                    }

                    // Temporary stop-gap until we have data flow analysis.
                    // Do not remove method declarations with generic types since the method invocation in `cu.getTypesInUse` will be bounded with a type.
                    for (JavaType.Method usedMethodType : cu.getTypesInUse().getDeclaredMethods()) {
                        if (methodType.getName().equals(usedMethodType.getName()) && methodType.equals(usedMethodType) && m.toString().contains("Generic{")) {
                            return m;
                        }
                    }

                    doAfterVisit(new RemoveUnusedImports().getVisitor());
                    //noinspection ConstantConditions
                    return null;
                }

                return m;
            }
        });
    }

}