fix single allof resulting in inheritance

modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java

@@ -1222,8 +1222,6 @@ public class ModelUtils {
     public static String getParentName(ComposedSchema composedSchema, Map<String, Schema> allSchemas) {
         List<Schema> interfaces = getInterfaces(composedSchema);
         int nullSchemaChildrenCount = 0;
-        boolean hasAmbiguousParents = false;
-        List<String> refedWithoutDiscriminator = new ArrayList<>();
 
         if (interfaces != null && !interfaces.isEmpty()) {
             for (Schema schema : interfaces) {
@@ -1238,9 +1236,10 @@ public class ModelUtils {
                         // discriminator.propertyName is used
                         return parentName;
                     } else {
-                        // not a parent since discriminator.propertyName is not set
-                        hasAmbiguousParents = true;
-                        refedWithoutDiscriminator.add(parentName);
+                        // TOOD to be removed in 6.x release
+                        LOGGER.warn("[deprecated] inheritance without use of 'discriminator.propertyName' has been deprecated" +
+                                        " in the 5.x release. Composed schema name: {}. Title: {}",
+                                composedSchema.getName(), composedSchema.getTitle());
                     }
                 } else {
                     // not a ref, doing nothing, except counting the number of times the 'null' type
@@ -1253,21 +1252,6 @@ public class ModelUtils {
                     }
                 }
             }
-            if (refedWithoutDiscriminator.size() == 1 && nullSchemaChildrenCount == 1) {
-                // One schema is a $ref and the other is the 'null' type, so the parent is obvious.
-                // In this particular case there is no need to specify a discriminator.
-                hasAmbiguousParents = false;
-            }
-        }
-
-        // parent name only makes sense when there is a single obvious parent
-        if (refedWithoutDiscriminator.size() == 1) {
-            if (hasAmbiguousParents) {
-                LOGGER.warn("[deprecated] inheritance without use of 'discriminator.propertyName' is deprecated " +
-                                "and will be removed in a future release. Generating model for composed schema name: {}. Title: {}",
-                        composedSchema.getName(), composedSchema.getTitle());
-            }
-            return refedWithoutDiscriminator.get(0);
         }
 
         return null;

modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java

@@ -1372,9 +1372,9 @@ public class DefaultCodegenTest {
         Schema schema = openAPI.getComponents().getSchemas().get("NewMessageEventCoreNoOwnProps");
         codegen.setOpenAPI(openAPI);
         CodegenModel model = codegen.fromModel("NewMessageEventCoreNoOwnProps", schema);
-        Assert.assertEquals(getNames(model.getVars()), Collections.emptyList());
-        Assert.assertEquals(model.parent, "MessageEventCore");
-        Assert.assertEquals(model.allParents, Collections.singletonList("MessageEventCore"));
+        Assert.assertEquals(getNames(model.getVars()), Arrays.asList("id","message"));
+        Assert.assertNull(model.parent);
+        Assert.assertNull(model.allParents);
     }
 
     class CodegenWithMultipleInheritance extends DefaultCodegen {

modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaInheritanceTest.java

@@ -25,6 +25,7 @@ import io.swagger.v3.oas.models.media.Discriminator;
 import io.swagger.v3.oas.models.media.ObjectSchema;
 import io.swagger.v3.oas.models.media.Schema;
 import io.swagger.v3.oas.models.media.StringSchema;
+import java.util.Collections;
 import org.apache.commons.lang3.StringUtils;
 import org.openapitools.codegen.CodegenModel;
 import org.openapitools.codegen.CodegenProperty;
@@ -57,8 +58,8 @@ public class JavaInheritanceTest {
 
         Assert.assertEquals(cm.name, "sample");
         Assert.assertEquals(cm.classname, "Sample");
-        Assert.assertEquals(cm.parent, "Base");
-        Assert.assertEquals(cm.imports, Sets.newHashSet("Base"));
+        Assert.assertNull(cm.parent);
+        Assert.assertEquals(cm.imports, Collections.emptySet());
     }
 
     @Test(description = "convert a composed model with discriminator")