Use description from child schema for ComposedSchema

Author: F43nd1r

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

@@ -2820,6 +2820,9 @@ protected void updateModelForComposedSchema(CodegenModel m, Schema schema, Map<S
 
                     // includes child's properties (all, required) in allProperties, allRequired
                     addProperties(allProperties, allRequired, component, new HashSet<>());
+
+                    // use description from child schema
+                    m.description = escapeText(component.getDescription());
                 }
                 // in 7.0.0 release, we comment out below to allow more than 1 child schemas in allOf
                 //break; // at most one child only

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

@@ -675,6 +675,36 @@ public void emptyModelKotlinxSerializationTest() throws IOException {
         TestUtils.assertFileNotContains(modelKt, "data class EmptyModel");
     }
 
+    @Test(description = "provide description in kdoc of polymorphic type")
+    public void testDescriptionOnPolymorphicType() throws IOException {
+        File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("kotlin")
+                .setLibrary("jvm-okhttp4")
+                .setAdditionalProperties(new HashMap<>() {{
+                    put(CodegenConstants.SERIALIZATION_LIBRARY, "jackson");
+                    put(CodegenConstants.MODEL_PACKAGE, "xyz.abcdef.model");
+                }})
+                .setInputSpec("src/test/resources/3_0/kotlin/polymorphism-description.yaml")
+                .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+        final ClientOptInput clientOptInput = configurator.toClientOptInput();
+        DefaultGenerator generator = new DefaultGenerator();
+        List<File> files = generator.opts(clientOptInput).generate();
+
+        Assert.assertEquals(files.size(), 28);
+
+        final Path animalKt = Paths.get(output + "/src/main/kotlin/xyz/abcdef/model/Animal.kt");
+        // base has description
+        TestUtils.assertFileContains(animalKt, "Description on supertype");
+
+        final Path birdKt = Paths.get(output + "/src/main/kotlin/xyz/abcdef/model/Bird.kt");
+        // derived has description
+        TestUtils.assertFileContains(birdKt, "Description on subtype");
+    }
+
     private static class ModelNameTest {
         private final String expectedName;
         private final String expectedClassName;

modules/openapi-generator/src/test/resources/3_0/kotlin/polymorphism-description.yaml

@@ -0,0 +1,39 @@
+openapi: 3.0.1
+info:
+  title: Example
+  version: '0.1'
+servers:
+  - url: http://example.org
+paths:
+  '/v1/bird':
+    get:
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/bird'
+      operationId: get-bird
+components:
+  schemas:
+    animal:
+      type: object
+      properties:
+        id:
+          type: string
+      required:
+        - id
+      discriminator:
+        propertyName: discriminator
+      description: 'Description on supertype'
+    bird:
+      type: object
+      allOf:
+        - $ref: '#/components/schemas/animal'
+        - properties:
+            featherType:
+              type: string
+          required:
+            - featherType
+          description: 'Description on subtype'