Support JSpecify on fields with default visibility

Fixes gh-447

Author: philwebb

spring-javaformat/spring-javaformat-formatter-tests/src/test/resources/expected/nullable.txt

@@ -1,5 +1,6 @@
 package example;
 
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 import org.jspecify.annotations.NullMarked;
 import org.jspecify.annotations.NullUnmarked;
@@ -34,4 +35,16 @@ public interface ExampleNullables {
 	@NullUnmarked
 	void withNullUnmarked(String str);
 
+	static class Fields {
+
+		@Nullable Object one;
+
+		@NonNull Object two;
+
+		private @Nullable Object three;
+
+		private @NonNull Object four;
+
+	}
+
 }

spring-javaformat/spring-javaformat-formatter-tests/src/test/resources/source/nullable.txt

@@ -1,5 +1,6 @@
 package example;
 
+import org.jspecify.annotations.NonNull;
 import org.jspecify.annotations.Nullable;
 import org.jspecify.annotations.NullMarked;
 import org.jspecify.annotations.NullUnmarked;
@@ -32,4 +33,16 @@ public interface ExampleNullables {
 	@NullUnmarked
 	void withNullUnmarked(String str);
 
+	static class Fields {
+
+		@Nullable Object one;
+
+		@NonNull Object two;
+
+		private @Nullable Object three;
+
+		private @NonNull Object four;
+
+	}
+
 }

spring-javaformat/spring-javaformat-formatter/src/main/java/io/spring/javaformat/formatter/jdk17/eclipse/JSpecifyPreparator.java

@@ -29,6 +29,7 @@
 import io.spring.javaformat.eclipse.jdt.jdk17.core.dom.ASTVisitor;
 import io.spring.javaformat.eclipse.jdt.jdk17.core.dom.Annotation;
 import io.spring.javaformat.eclipse.jdt.jdk17.core.dom.CompilationUnit;
+import io.spring.javaformat.eclipse.jdt.jdk17.core.dom.FieldDeclaration;
 import io.spring.javaformat.eclipse.jdt.jdk17.core.dom.IExtendedModifier;
 import io.spring.javaformat.eclipse.jdt.jdk17.core.dom.ImportDeclaration;
 import io.spring.javaformat.eclipse.jdt.jdk17.core.dom.MethodDeclaration;
@@ -85,6 +86,12 @@ public boolean visit(ImportDeclaration node) {
 			return super.visit(node);
 		}
 
+		@Override
+		public boolean visit(FieldDeclaration node) {
+			clearLineBreaksIfHasJSpecifyAnnotation(node.modifiers());
+			return super.visit(node);
+		}
+
 		@Override
 		public boolean visit(MethodDeclaration node) {
 			clearLineBreaksIfHasJSpecifyAnnotation(node.modifiers());

spring-javaformat/spring-javaformat-formatter/src/main/java/io/spring/javaformat/formatter/jdk8/eclipse/JSpecifyPreparator.java

@@ -29,6 +29,7 @@
 import io.spring.javaformat.eclipse.jdt.jdk8.core.dom.ASTVisitor;
 import io.spring.javaformat.eclipse.jdt.jdk8.core.dom.Annotation;
 import io.spring.javaformat.eclipse.jdt.jdk8.core.dom.CompilationUnit;
+import io.spring.javaformat.eclipse.jdt.jdk8.core.dom.FieldDeclaration;
 import io.spring.javaformat.eclipse.jdt.jdk8.core.dom.IExtendedModifier;
 import io.spring.javaformat.eclipse.jdt.jdk8.core.dom.ImportDeclaration;
 import io.spring.javaformat.eclipse.jdt.jdk8.core.dom.MethodDeclaration;
@@ -85,6 +86,12 @@ public boolean visit(ImportDeclaration node) {
 			return super.visit(node);
 		}
 
+		@Override
+		public boolean visit(FieldDeclaration node) {
+			clearLineBreaksIfHasJSpecifyAnnotation(node.modifiers());
+			return super.visit(node);
+		}
+
 		@Override
 		public boolean visit(MethodDeclaration node) {
 			clearLineBreaksIfHasJSpecifyAnnotation(node.modifiers());