Skip UseEnumSetOf empty conversion for static fields to avoid circular class-init (#1157) (#1161)

* Skip UseEnumSetOf empty conversion for static fields to avoid circular class-init (#1157)

* Prevent conversion of empty Set.of() in static fields

Skip conversion for empty Set.of() in static field initializers to avoid ClassCastException.

Author: timtebeek

src/main/java/org/openrewrite/java/migrate/util/UseEnumSetOf.java

@@ -78,6 +78,9 @@ public J.MethodInvocation visitMethodInvocation(J.MethodInvocation methodInvocat
                             }
 
                             if (args.get(0) instanceof J.Empty) {
+                                if (isStaticField(parent)) {
+                                    return mi;
+                                }
                                 JavaType firstTypeParameter = ((JavaType.Parameterized) type).getTypeParameters().get(0);
                                 JavaType.ShallowClass shallowClass = JavaType.ShallowClass.build(firstTypeParameter.toString());
                                 return JavaTemplate.builder("EnumSet.noneOf(" + shallowClass.getClassName() + ".class)")
@@ -120,6 +123,11 @@ private boolean isAssignmentSetOfEnum(@Nullable JavaType type) {
                 return false;
             }
 
+            private boolean isStaticField(Cursor parent) {
+                return parent.getValue() instanceof J.VariableDeclarations &&
+                        ((J.VariableDeclarations) parent.getValue()).hasModifier(J.Modifier.Type.Static);
+            }
+
             private boolean isArrayParameter(final List<Expression> args) {
                 if (args.size() != 1) {
                     return false;

src/test/java/org/openrewrite/java/migrate/util/UseEnumSetOfTest.java

@@ -182,6 +182,45 @@ public void method() {
         );
     }
 
+    @Issue("https://github.com/openrewrite/rewrite-migrate-java/issues/1157")
+    @Test
+    void dontConvertEmptySetOfInStaticField() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              package com.helloworld;
+
+              import java.util.Set;
+
+              public enum ConfigType {
+                ENUM,
+                BOOLEAN,
+                INTEGER;
+
+                public static final Set<ConfigProperty> SUBSCRIBE_TO_ALL = Set.<ConfigProperty>of();
+              }
+              """,
+            spec -> spec.markers(javaVersion(25))),
+          java(
+            """
+              package com.helloworld;
+
+              import static com.helloworld.ConfigType.BOOLEAN;
+              import static com.helloworld.ConfigType.ENUM;
+              import static com.helloworld.ConfigType.INTEGER;
+
+              public enum ConfigProperty {
+                TRIAL_TYPE(ENUM),
+                IS_TRIAL_ENABLED(BOOLEAN),
+                MIN_ACCOUNT_AGE_MINUTES(INTEGER);
+
+                ConfigProperty(final ConfigType type) {}
+              }
+              """,
+            spec -> spec.markers(javaVersion(25))));
+    }
+
     @Issue("https://github.com/openrewrite/rewrite-migrate-java/issues/958")
     @Test
     void retainEmptySetOf() {