From c8f92630f154adf4c1fd9ae658fe499e1a1206c5 Mon Sep 17 00:00:00 2001
From: Michael Nahkies <michael@nahkies.co.nz>
Date: Tue, 27 Aug 2019 21:40:22 +0100
Subject: [PATCH] [core] [regression] set parentName when a single possible
 parent exists

Whilst the spec states that the 'allOf' relationship does not imply a hierarchy:

> While composition offers model extensibility, it does not imply a hierarchy between the models.
> To support polymorphism, the OpenAPI Specification adds the discriminator field.

Unfortunately this does not make sense for many existing use cases, that were supported by older
versions of the generator. Therefore, I've restored the older behavior, specifically
in the case that only a single possible parent schema is present.

I think a more complete solution would generate interfaces for the composed schemas,
and mark the generated class as implementing these.

fixes issue 2845, and fixes issue #3523
---
 .../org/openapitools/codegen/utils/ModelUtils.java     | 10 ++++++++++
 .../openapitools/codegen/java/JavaInheritanceTest.java |  9 +++++----
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java
index ad991f679545..50c9250224bd 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java
@@ -896,6 +896,8 @@ public static List<Schema> getInterfaces(ComposedSchema composed) {
     public static String getParentName(ComposedSchema composedSchema, Map<String, Schema> allSchemas) {
         List<Schema> interfaces = getInterfaces(composedSchema);
 
+        List<String> refedParentNames = new ArrayList<>();
+
         if (interfaces != null && !interfaces.isEmpty()) {
             for (Schema schema : interfaces) {
                 // get the actual schema
@@ -911,6 +913,7 @@ public static String getParentName(ComposedSchema composedSchema, Map<String, Sc
                     } else {
                         LOGGER.debug("Not a parent since discriminator.propertyName is not set {}", s.get$ref());
                         // not a parent since discriminator.propertyName is not set
+                        refedParentNames.add(parentName);
                     }
                 } else {
                     // not a ref, doing nothing
@@ -918,6 +921,13 @@ public static String getParentName(ComposedSchema composedSchema, Map<String, Sc
             }
         }
 
+        // parent name only makes sense when there is a single obvious parent
+        if (refedParentNames.size() == 1) {
+            LOGGER.warn("[deprecated] inheritance without use of 'discriminator.propertyName' is deprecated " +
+                    "and will be removed in a future release. Generating model for {}", composedSchema.getName());
+            return refedParentNames.get(0);
+        }
+
         return null;
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaInheritanceTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaInheritanceTest.java
index 80bf59d12c2f..3b8d691fac91 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaInheritanceTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaInheritanceTest.java
@@ -32,9 +32,10 @@
 
 public class JavaInheritanceTest {
 
-    @Test(description = "convert a composed model without discriminator")
+
+    @Test(description = "convert a composed model with parent")
     public void javaInheritanceTest() {
-        final Schema allOfModel = new Schema().name("Base");
+        final Schema parentModel = new Schema().name("Base");
 
         final Schema schema = new ComposedSchema()
                 .addAllOfItem(new Schema().$ref("Base"))
@@ -42,7 +43,7 @@ public void javaInheritanceTest() {
 
         OpenAPI openAPI = TestUtils.createOpenAPI();
         openAPI.setComponents(new Components()
-                .addSchemas(allOfModel.getName(), allOfModel)
+                .addSchemas(parentModel.getName(),parentModel)
                 .addSchemas(schema.getName(), schema)
         );
 
@@ -52,7 +53,7 @@ public void javaInheritanceTest() {
 
         Assert.assertEquals(cm.name, "sample");
         Assert.assertEquals(cm.classname, "Sample");
-        Assert.assertEquals(cm.parent, null);
+        Assert.assertEquals(cm.parent, "Base");
         Assert.assertEquals(cm.imports, Sets.newHashSet("Base"));
     }