fix RemoveUnusedPrivateMethods: getHostDottedClassName

Author: Vincent Potucek

src/main/java/org/openrewrite/staticanalysis/RemoveUnusedPrivateMethods.java

@@ -21,11 +21,11 @@
 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.util.List;
 import java.util.Set;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import static java.util.Collections.singleton;
 
@@ -75,53 +75,100 @@ private boolean unusedWarningsSuppressed(J classDeclaration) {
             @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()) {
+                if (methodType == null) {
+                    return m;
+                }
+
+                // Only consider private, non-constructors.
+                if (!methodType.hasFlags(Flag.Private) || method.isConstructor()) {
+                    return m;
+                }
+
+                // Serialization hooks & similar: do not remove even if private.
+                switch (m.getSimpleName()) {
+                    case "readObject":
+                    case "readObjectNoData":
+                    case "readResolve":
+                    case "writeObject":
+                    case "writeReplace":
+                        return m;
+                }
 
-                    J.ClassDeclaration classDeclaration = getCursor().firstEnclosing(J.ClassDeclaration.class);
-                    if (classDeclaration == null) {
+                // If we're missing the enclosing class or CU, bail out.
+                J.ClassDeclaration classDeclaration = getCursor().firstEnclosing(J.ClassDeclaration.class);
+                if (classDeclaration == null) {
+                    return m;
+                }
+                JavaSourceFile cu = getCursor().firstEnclosingOrThrow(JavaSourceFile.class);
+
+                // If referenced anywhere in TypesInUse (e.g., via other classes), keep it.
+                for (JavaType.Method usedMethodType : cu.getTypesInUse().getUsedMethods()) {
+                    if (methodType.equals(usedMethodType)) {
                         return m;
                     }
-                    switch (m.getSimpleName()) {
-                        case "readObject":
-                        case "readObjectNoData":
-                        case "readResolve":
-                        case "writeObject":
-                        case "writeReplace":
-                            return m;
+                }
+
+                // Do not touch if the compilation unit references JUnit's MethodSource (reflective use).
+                for (JavaType javaType : cu.getTypesInUse().getTypesInUse()) {
+                    if (TypeUtils.isOfClassType(javaType, "org.junit.jupiter.params.provider.MethodSource")) {
+                        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;
-                        }
+                // Temporary stop-gap until we have DFA:
+                // If the declared method shows generic type artifacts, be conservative and keep it.
+                for (JavaType.Method declared : cu.getTypesInUse().getDeclaredMethods()) {
+                    if (methodType.equals(declared) && m.toString().contains("Generic{")) {
+                        return m;
                     }
+                }
 
-                    for (JavaType javaType : cu.getTypesInUse().getTypesInUse()) {
-                        if (TypeUtils.isOfClassType(javaType, "org.junit.jupiter.params.provider.MethodSource")) {
-                            return m;
+                // Scan the enclosing class for in-class usages (method calls or method references).
+                // IMPORTANT: self-recursion alone does NOT count as usage.
+                AtomicBoolean usedInClass = new AtomicBoolean(false);
+
+                new JavaIsoVisitor<ExecutionContext>() {
+                    @Override
+                    public J.MethodInvocation visitMethodInvocation(J.MethodInvocation call, ExecutionContext ctx2) {
+                        J.MethodInvocation c = super.visitMethodInvocation(call, ctx2);
+                        JavaType.Method calledType = c.getMethodType();
+                        if (calledType != null && calledType.equals(methodType)) {
+                            // Ignore self-recursion: only count if the enclosing method is NOT the same declaration.
+                            J.MethodDeclaration enclosing = getCursor().firstEnclosing(J.MethodDeclaration.class);
+                            if (enclosing == null || enclosing != method) {
+                                usedInClass.set(true);
+                            }
                         }
+                        return c;
                     }
 
-                    // 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;
+                    @Override
+                    public J.MemberReference visitMemberReference(J.MemberReference ref, ExecutionContext ctx2) {
+                        J.MemberReference r = super.visitMemberReference(ref, ctx2);
+                        JavaType.Method refType = r.getMethodType();
+                        if (refType != null && refType.equals(methodType)) {
+                            J.MethodDeclaration enclosing = getCursor().firstEnclosing(J.MethodDeclaration.class);
+                            if (enclosing == null || enclosing != method) {
+                                usedInClass.set(true);
+                            }
                         }
+                        return r;
                     }
+                }.visit(classDeclaration, ctx);
 
-                    doAfterVisit(new RemoveUnusedImports().getVisitor());
-                    //noinspection ConstantConditions
-                    return null;
+                if (usedInClass.get()) {
+                    return m;
                 }
 
-                return m;
+                // No external nor internal usages -> remove it.
+                doAfterVisit(new RemoveUnusedImports().getVisitor());
+                //noinspection ConstantConditions
+                return null;
             }
         };
+
         return Preconditions.check(new NoMissingTypes(), Repeat.repeatUntilStable(visitor));
     }
 }