Models are now typed as Object when properties of another Model

Description

This was asked in chat, and I've done some evaluation to determine what's going on. Models which are properties of other models are now considered Object rather than the property type.

diff --git a/samples/client/petstore/kotlin/docs/Pet.md b/samples/client/petstore/kotlin/docs/Pet.md
index ec7756007..4b25ccb3e 100644
--- a/samples/client/petstore/kotlin/docs/Pet.md
+++ b/samples/client/petstore/kotlin/docs/Pet.md
@@ -5,7 +5,7 @@
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
 **id** | **kotlin.Long** |  |  [optional]
-**category** | [**Category**](Category.md) |  |  [optional]
+**category** | [**kotlin.Any**](kotlin.Any.md) | A category for a pet |  [optional]
 **name** | **kotlin.String** |  | 
 **photoUrls** | **kotlin.Array<kotlin.String>** |  | 
 **tags** | [**kotlin.Array<Tag>**](Tag.md) |  |  [optional]
diff --git a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/models/Pet.kt b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/models/Pet.kt
index 583dd3fb3..3ca832e7b 100644
--- a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/models/Pet.kt
+++ b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/models/Pet.kt
@@ -11,14 +11,13 @@
 */
 package org.openapitools.client.models
 
-import org.openapitools.client.models.Category
 import org.openapitools.client.models.Tag
 
 import com.squareup.moshi.Json
 /**
  * A pet for sale in the pet store
  * @param id 
- * @param category 
+ * @param category A category for a pet
  * @param name 
  * @param photoUrls 
  * @param tags 
@@ -28,7 +27,8 @@ data class Pet (
     val name: kotlin.String,
     val photoUrls: kotlin.Array<kotlin.String>,
     val id: kotlin.Long? = null,
-    val category: Category? = null,
+    /* A category for a pet */
+    val category: kotlin.Any? = null,
     val tags: kotlin.Array<Tag>? = null,
     /* pet status in the store */
     val status: Pet.Status? = null

Apparently, our petstore example for many generated samples only nest models once (Category under Pet#category). This bug appears to happen for any nested models. Nested enums and arrays of types are unaffected.

openapi-generator version

master (752b36e6)

OpenAPI declaration file content or url

n/a

Command line used for generation

Any generator under ./bin with nested models

Steps to reproduce

• pull current master branch (752b36e6)
• execute mvn clean package install
• execute ./bin/kotlin-client-petstore.sh
• execute cat samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/models/Pet.kt

Notice that category is now kotlin.Any? rather than Category as it was previously.

Related issues/PRs

• Introduced via #45

Suggest a fix/enhancement

Nothing substantial to suggest. Maybe copying non-empty properties to the new schema rather than replacing the reference?

---

@jmini you commented in the PR that the fix is temporary. However, I consider the issue a significant one.

It looks like this block is the bug:

+            Schema prop = entry.getValue();
+            if (allDefinitions != null && prop != null && StringUtils.isNotEmpty(prop.get$ref())) {
+                String refName = ModelUtils.getSimpleRef(prop.get$ref());
+                prop = allDefinitions.get(refName);
+            }

I haven't stepped through the code to verify, but it seems to me that this would be falling back to Object where it shouldn't be. I saw that you opened a bug with swagger-parser for the json-schema properties that don't get exposed as expected. I think that parser bug is unrelated to this bug.

For reference, I tracked this down via git bisect using:

• GOOD f22d0cf5
• BAD b5a0d173
• RUN https://gist.github.com/jimschubert/38fe5491aa0c25df9d2c8c13d327a1b6

Would you mind giving this a quick look? I had planned to get into a fix, but I wasted a big of time with my evaluation script (running kotlin-client generator, then checking kotlin-server output produced only HEAD as the bad commit).