Add reproducer test self-referencing (#1565) (#1636)

* Reproduce issue #1565

Branch off 3.5.2 as that's what included in Quarkus 3.4.x where I
encountered the bug.

Later I realised that it was already fixed in 3.6.x (Quarkus 3.5.0)

* Rename and improve test for #1565

* Format code according to formatter configuration

core/src/test/java/io/smallrye/openapi/runtime/scanner/OpenApiDataObjectScannerTest.java

@@ -1,16 +1,20 @@
 package io.smallrye.openapi.runtime.scanner;
 
+import static org.junit.jupiter.api.Assertions.assertAll;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
 
 import java.io.IOException;
 
+import org.eclipse.microprofile.openapi.annotations.enums.SchemaType;
 import org.eclipse.microprofile.openapi.models.media.Schema;
 import org.jboss.jandex.DotName;
 import org.jboss.jandex.Index;
 import org.jboss.jandex.IndexView;
 import org.jboss.jandex.Type;
 import org.jboss.jandex.Type.Kind;
 import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.CsvSource;
 
@@ -41,4 +45,42 @@ void testStreams(String type, Schema.SchemaType itemType, String itemFormat) thr
         assertEquals(itemFormat, out.getItems().getFormat());
     }
 
+    @Test
+    void testNoSelfReferencingRegardlessOfScanOrder() throws IOException {
+        // one way to trigger issue 1565 (self-referencing) was to have a
+        // non-SchemaType.OBJECT type as a field in another type
+        @org.eclipse.microprofile.openapi.annotations.media.Schema(description = "Nested class", type = SchemaType.STRING)
+        class N {
+        }
+
+        @org.eclipse.microprofile.openapi.annotations.media.Schema(description = "Containing class")
+        class C {
+            N n;
+        }
+
+        IndexView index = Index.of(C.class, N.class);
+        AnnotationScannerContext contextCFirst = new AnnotationScannerContext(index,
+                Thread.currentThread().getContextClassLoader(),
+                IndexScannerTestBase.emptyConfig());
+        AnnotationScannerContext contextNFirst = new AnnotationScannerContext(index,
+                Thread.currentThread().getContextClassLoader(),
+                IndexScannerTestBase.emptyConfig());
+        Type cType = Type.create(DotName.createSimple(C.class), Kind.CLASS);
+        Type nType = Type.create(DotName.createSimple(N.class), Kind.CLASS);
+
+        // io.smallrye.openapi.runtime.scanner.OpenApiAnnotationScanner.processClassSchemas()
+        // calls OpenApiDataObjectScanner.process() for all annotated classes in 'index',
+        // and the order of the calls might not be deterministic.
+        // Try both orders for the two example classes and expect the same result
+        OpenApiDataObjectScanner.process(contextCFirst, cType);
+        OpenApiDataObjectScanner.process(contextCFirst, nType);
+
+        OpenApiDataObjectScanner.process(contextNFirst, nType);
+        OpenApiDataObjectScanner.process(contextNFirst, cType);
+
+        // the contextCFirst case had "#/components/schemas/1N" from getRef() in smallrye-open-api 3.5.2
+        assertAll(
+                () -> assertNull(contextCFirst.getOpenApi().getComponents().getSchemas().get("1N").getRef(), "C first"),
+                () -> assertNull(contextNFirst.getOpenApi().getComponents().getSchemas().get("1N").getRef(), "N first"));
+    }
 }