Better support for $ref to schema's properties

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

@@ -2464,6 +2464,14 @@ public Schema unaliasSchema(Schema schema) {
     protected String getSingleSchemaType(Schema schema) {
         Schema unaliasSchema = unaliasSchema(schema);
 
+        if (ModelUtils.isRefToSchemaWithProperties(unaliasSchema.get$ref())) {
+            // ref to schema's properties, e.g. #/components/schemas/Pet/properties/category
+            Schema refSchema = ModelUtils.getReferencedSchema(openAPI, unaliasSchema);
+            if (refSchema != null) {
+                return getSingleSchemaType(refSchema);
+            }
+        }
+
         if (StringUtils.isNotBlank(unaliasSchema.get$ref())) { // reference to another definition/schema
             // get the schema/model name from $ref
             String schemaName = ModelUtils.getSimpleRef(unaliasSchema.get$ref());
@@ -3354,7 +3362,7 @@ private CodegenProperty discriminatorFound(String composedSchemaName, Schema sc,
                     String modelName = ModelUtils.getSimpleRef(((Schema) oneOf).get$ref());
                     CodegenProperty thisCp = discriminatorFound(composedSchemaName, (Schema) oneOf, discPropName, visitedSchemas);
                     if (thisCp == null) {
-                        LOGGER.warn(
+                        once(LOGGER).warn(
                                 "'{}' defines discriminator '{}', but the referenced OneOf schema '{}' is missing {}",
                                 composedSchemaName, discPropName, modelName, discPropName);
                     }
@@ -3363,7 +3371,7 @@ private CodegenProperty discriminatorFound(String composedSchemaName, Schema sc,
                         continue;
                     }
                     if (cp != thisCp) {
-                        LOGGER.warn(
+                        once(LOGGER).warn(
                                 "'{}' defines discriminator '{}', but the OneOf schema '{}' has a different {} definition than the prior OneOf schema's. Make sure the {} type and required values are the same",
                                 composedSchemaName, discPropName, modelName, discPropName, discPropName);
                     }
@@ -3377,7 +3385,7 @@ private CodegenProperty discriminatorFound(String composedSchemaName, Schema sc,
                     String modelName = ModelUtils.getSimpleRef(((Schema) anyOf).get$ref());
                     CodegenProperty thisCp = discriminatorFound(composedSchemaName, (Schema) anyOf, discPropName, visitedSchemas);
                     if (thisCp == null) {
-                        LOGGER.warn(
+                        once(LOGGER).warn(
                                 "'{}' defines discriminator '{}', but the referenced AnyOf schema '{}' is missing {}",
                                 composedSchemaName, discPropName, modelName, discPropName);
                     }
@@ -3386,7 +3394,7 @@ private CodegenProperty discriminatorFound(String composedSchemaName, Schema sc,
                         continue;
                     }
                     if (cp != thisCp) {
-                        LOGGER.warn(
+                        once(LOGGER).warn(
                                 "'{}' defines discriminator '{}', but the AnyOf schema '{}' has a different {} definition than the prior AnyOf schema's. Make sure the {} type and required values are the same",
                                 composedSchemaName, discPropName, modelName, discPropName, discPropName);
                     }
@@ -3454,7 +3462,7 @@ private Discriminator recursiveGetDiscriminator(Schema sc, ArrayList<Schema> vis
                     }
                 }
                 if (discriminatorsPropNames.size() > 1) {
-                    LOGGER.warn("The oneOf schemas have conflicting discriminator property names. " +
+                    once(LOGGER).warn("The oneOf schemas have conflicting discriminator property names. " +
                             "oneOf schemas must have the same property name, but found " + String.join(", ", discriminatorsPropNames));
                 }
                 if (foundDisc != null && (hasDiscriminatorCnt + hasNullTypeCnt) == composedSchema.getOneOf().size() && discriminatorsPropNames.size() == 1) {
@@ -3483,7 +3491,7 @@ private Discriminator recursiveGetDiscriminator(Schema sc, ArrayList<Schema> vis
                     }
                 }
                 if (discriminatorsPropNames.size() > 1) {
-                    LOGGER.warn("The anyOf schemas have conflicting discriminator property names. " +
+                    once(LOGGER).warn("The anyOf schemas have conflicting discriminator property names. " +
                             "anyOf schemas must have the same property name, but found " + String.join(", ", discriminatorsPropNames));
                 }
                 if (foundDisc != null && (hasDiscriminatorCnt + hasNullTypeCnt) == composedSchema.getAnyOf().size() && discriminatorsPropNames.size() == 1) {
@@ -3532,7 +3540,7 @@ protected List<MappedModel> getOneOfAnyOfDescendants(String composedSchemaName,
                     // schemas also has inline composed schemas
                     // Note: if it is only inline one level, then the inline model resolver will move it into its own
                     // schema and make it a $ref schema in the oneOf/anyOf location
-                    LOGGER.warn(
+                    once(LOGGER).warn(
                             "Invalid inline schema defined in oneOf/anyOf in '{}'. Per the OpenApi spec, for this case when a composed schema defines a discriminator, the oneOf/anyOf schemas must use $ref. Change this inline definition to a $ref definition",
                             composedSchemaName);
                 }
@@ -3554,14 +3562,14 @@ protected List<MappedModel> getOneOfAnyOfDescendants(String composedSchemaName,
                             msgSuffix += spacer + "invalid optional definition of " + discPropName + ", include it in required";
                         }
                     }
-                    LOGGER.warn("'{}' defines discriminator '{}', but the referenced schema '{}' is incorrect. {}",
+                    once(LOGGER).warn("'{}' defines discriminator '{}', but the referenced schema '{}' is incorrect. {}",
                             composedSchemaName, discPropName, modelName, msgSuffix);
                 }
                 MappedModel mm = new MappedModel(modelName, toModelName(modelName));
                 descendentSchemas.add(mm);
                 Schema cs = ModelUtils.getSchema(openAPI, modelName);
                 if (cs == null) { // cannot lookup the model based on the name
-                    LOGGER.error("Failed to lookup the schema '{}' when processing oneOf/anyOf. Please check to ensure it's defined properly.", modelName);
+                    once(LOGGER).error("Failed to lookup the schema '{}' when processing oneOf/anyOf. Please check to ensure it's defined properly.", modelName);
                 } else {
                     Map<String, Object> vendorExtensions = cs.getExtensions();
                     if (vendorExtensions != null && !vendorExtensions.isEmpty() && vendorExtensions.containsKey("x-discriminator-value")) {
@@ -3674,7 +3682,7 @@ protected CodegenDiscriminator createDiscriminator(String schemaName, Schema sch
                 if (e.getValue().indexOf('/') >= 0) {
                     name = ModelUtils.getSimpleRef(e.getValue());
                     if (ModelUtils.getSchema(openAPI, name) == null) {
-                        LOGGER.error("Failed to lookup the schema '{}' when processing the discriminator mapping of oneOf/anyOf. Please check to ensure it's defined properly.", name);
+                        once(LOGGER).error("Failed to lookup the schema '{}' when processing the discriminator mapping of oneOf/anyOf. Please check to ensure it's defined properly.", name);
                     }
                 } else {
                     name = e.getValue();
@@ -3983,6 +3991,13 @@ public CodegenProperty fromProperty(String name, Schema p, boolean required, boo
             return cpc;
         }
 
+        // if it's ref to schema's properties, get the actual schema defined in the properties
+        Schema refToPropertiesSchema = ModelUtils.getSchemaFromRefToSchemaWithProperties(openAPI, p.get$ref());
+        if (refToPropertiesSchema != null) {
+            p = refToPropertiesSchema;
+            return fromProperty(name, refToPropertiesSchema, required, schemaIsFromAdditionalProperties);
+        }
+
         Schema original = null;
         // check if it's allOf (only 1 sub schema) with or without default/nullable/etc set in the top level
         if (ModelUtils.isAllOf(p) && p.getAllOf().size() == 1) {

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

@@ -929,16 +929,76 @@ public static boolean shouldGenerateArrayModel(Schema schema) {
      * @return schema without '$ref'
      */
     public static Schema getReferencedSchema(OpenAPI openAPI, Schema schema) {
-        if (schema != null && StringUtils.isNotEmpty(schema.get$ref())) {
-            String name = getSimpleRef(schema.get$ref());
-            Schema referencedSchema = getSchema(openAPI, name);
-            if (referencedSchema != null) {
-                return referencedSchema;
+        if (schema == null) {
+            return null;
+        }
+
+        if (StringUtils.isEmpty(schema.get$ref())) {
+            return schema;
+        }
+
+        try {
+            Schema refSchema = getSchemaFromRefToSchemaWithProperties(openAPI, schema.get$ref());
+            if (refSchema != null) {
+                // it's ref to schema's properties, #/components/schemas/Pet/properties/category for example
+                return refSchema;
             }
+        } catch (Exception e) {
+            LOGGER.warn("Failed to parse $ref {}. Please report the issue to openapi-generator GitHub repo.", schema.get$ref());
         }
+
+        // a simple ref, e.g. #/components/schemas/Pet
+        String name = getSimpleRef(schema.get$ref());
+        Schema referencedSchema = getSchema(openAPI, name);
+        if (referencedSchema != null) {
+            return referencedSchema;
+        }
+
         return schema;
     }
 
+    /**
+     * Get the schema referenced by $ref to schema's properties, e.g. #/components/schemas/Pet/properties/category.
+     *
+     * @param openAPI    specification being checked
+     * @param refString  schema reference
+     * @return schema
+     */
+    public static Schema getSchemaFromRefToSchemaWithProperties(OpenAPI openAPI, String refString) {
+        if (refString == null) {
+            return null;
+        }
+
+        String[] parts = refString.split("/");
+        // #/components/schemas/Pet/properties/category
+        if (parts.length == 6 && "properties".equals(parts[4])) {
+            Schema referencedSchema = getSchema(openAPI, parts[3]); // parts[3] is Pet
+            return (Schema) referencedSchema.getProperties().get(parts[5]); // parts[5] is category
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Returns true if $ref to a reference to schema's properties, e.g. #/components/schemas/Pet/properties/category.
+     *
+     * @param refString  schema reference
+     * @return true if $ref to a reference to schema's properties
+     */
+    public static boolean isRefToSchemaWithProperties(String refString) {
+        if (refString == null) {
+            return false;
+        }
+
+        String[] parts = refString.split("/");
+        // #/components/schemas/Pet/properties/category
+        if (parts.length == 6 && "properties".equals(parts[4])) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+
     public static Schema getSchema(OpenAPI openAPI, String name) {
         if (name == null) {
             return null;
@@ -1272,7 +1332,9 @@ public static Schema unaliasSchema(OpenAPI openAPI,
             }
             Schema ref = allSchemas.get(simpleRef);
             if (ref == null) {
-                once(LOGGER).warn("{} is not defined", schema.get$ref());
+                if (!isRefToSchemaWithProperties(schema.get$ref())) {
+                    once(LOGGER).warn("{} is not defined", schema.get$ref());
+                }
                 return schema;
             } else if (ref.getEnum() != null && !ref.getEnum().isEmpty()) {
                 // top-level enum class

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

@@ -295,6 +295,25 @@ public void testSimpleRefDecoding() {
         Assert.assertEquals(decoded, "~1 Hallo/Welt");
     }
 
+    @Test
+    public void testRefToSchemaProperties() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/petstore.yaml");
+
+        Schema category = ModelUtils.getSchemaFromRefToSchemaWithProperties(openAPI, "#/components/schemas/Pet/properties/category");
+        Assert.assertEquals(category.get$ref(), "#/components/schemas/Category");
+
+        Schema name = ModelUtils.getSchemaFromRefToSchemaWithProperties(openAPI, "#/components/schemas/Pet/properties/name");
+        Assert.assertEquals(name.getType(), "string");
+
+        Schema id = ModelUtils.getSchemaFromRefToSchemaWithProperties(openAPI, "#/components/schemas/Pet/properties/id");
+        Assert.assertEquals(id.getType(), "integer");
+        Assert.assertEquals(id.getFormat(), "int64");
+
+        Assert.assertEquals(null, ModelUtils.getSchemaFromRefToSchemaWithProperties(openAPI, "#/components/schemas/Pet/prop/category"));
+        Assert.assertEquals(null, ModelUtils.getSchemaFromRefToSchemaWithProperties(openAPI, "#/components/schemas/Pet/properties/categoryyyy"));
+        Assert.assertEquals(null, ModelUtils.getSchemaFromRefToSchemaWithProperties(openAPI, "#/components/schemas/Pet"));
+    }
+
 
     // 3.0 spec tests
     @Test

modules/openapi-generator/src/test/resources/3_0/java/petstore-with-fake-endpoints-models-for-testing-okhttp-gson.yaml

@@ -2655,3 +2655,23 @@ components:
     PetComposition:
       allOf:
         - $ref: '#/components/schemas/Pet'
+    PetRef:
+      type: object
+      required:
+        - name
+        - photoUrls
+      properties:
+        id:
+          $ref: '#/components/schemas/Pet/properties/id'
+        category:
+          $ref: '#/components/schemas/Pet/properties/category'
+        name:
+          $ref: '#/components/schemas/Pet/properties/name'
+        photoUrls:
+          $ref: '#/components/schemas/Pet/properties/photoUrls'
+        tags:
+          $ref: '#/components/schemas/Pet/properties/tags'
+        status:
+          $ref: '#/components/schemas/Pet/properties/status'
+      xml:
+        name: Pet

samples/client/petstore/java/okhttp-gson/.openapi-generator/FILES

@@ -79,6 +79,7 @@ docs/ParentPet.md
 docs/Pet.md
 docs/PetApi.md
 docs/PetComposition.md
+docs/PetRef.md
 docs/PetUsingAllOf.md
 docs/PetWithRequiredTags.md
 docs/Pig.md
@@ -213,6 +214,7 @@ src/main/java/org/openapitools/client/model/OuterEnumIntegerDefaultValue.java
 src/main/java/org/openapitools/client/model/ParentPet.java
 src/main/java/org/openapitools/client/model/Pet.java
 src/main/java/org/openapitools/client/model/PetComposition.java
+src/main/java/org/openapitools/client/model/PetRef.java
 src/main/java/org/openapitools/client/model/PetUsingAllOf.java
 src/main/java/org/openapitools/client/model/PetWithRequiredTags.java
 src/main/java/org/openapitools/client/model/Pig.java

samples/client/petstore/java/okhttp-gson/README.md

@@ -235,6 +235,7 @@ Class | Method | HTTP request | Description
  - [ParentPet](docs/ParentPet.md)
  - [Pet](docs/Pet.md)
  - [PetComposition](docs/PetComposition.md)
+ - [PetRef](docs/PetRef.md)
  - [PetUsingAllOf](docs/PetUsingAllOf.md)
  - [PetWithRequiredTags](docs/PetWithRequiredTags.md)
  - [Pig](docs/Pig.md)

samples/client/petstore/java/okhttp-gson/api/openapi.yaml

@@ -2691,6 +2691,26 @@ components:
     PetComposition:
       allOf:
       - $ref: '#/components/schemas/Pet'
+    PetRef:
+      properties:
+        id:
+          $ref: '#/components/schemas/Pet/properties/id'
+        category:
+          $ref: '#/components/schemas/Pet/properties/category'
+        name:
+          $ref: '#/components/schemas/Pet/properties/name'
+        photoUrls:
+          $ref: '#/components/schemas/Pet/properties/photoUrls'
+        tags:
+          $ref: '#/components/schemas/Pet/properties/tags'
+        status:
+          $ref: '#/components/schemas/Pet/properties/status'
+      required:
+      - name
+      - photoUrls
+      type: object
+      xml:
+        name: Pet
     _foo_get_default_response:
       example:
         string:

samples/client/petstore/java/okhttp-gson/docs/PetRef.md

@@ -0,0 +1,28 @@
+
+
+# PetRef
+
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**id** | **Long** |  |  [optional] |
+|**category** | [**Category**](Category.md) |  |  [optional] |
+|**name** | **String** |  |  |
+|**photoUrls** | **List<String>** |  |  |
+|**tags** | [**List<Tag>**](Tag.md) |  |  [optional] |
+|**status** | [**StatusEnum**](#StatusEnum) | pet status in the store |  [optional] |
+
+
+
+## Enum: StatusEnum
+
+| Name | Value |
+|---- | -----|
+| AVAILABLE | "available" |
+| PENDING | "pending" |
+| SOLD | "sold" |
+
+
+

samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/JSON.java

@@ -298,6 +298,7 @@ private static Class getClassByDiscriminator(Map classByDiscriminatorValue, Stri
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.ParentPet.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.Pet.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.PetComposition.CustomTypeAdapterFactory());
+        gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.PetRef.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.PetUsingAllOf.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.PetWithRequiredTags.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new org.openapitools.client.model.Pig.CustomTypeAdapterFactory());