Kotlin collection type (#1564)

* Allow specifying type

* Add test

* Update docs

* Don't modify types if the default option is chosen

docs/generators/kotlin.md

@@ -28,4 +28,9 @@ CONFIG OPTIONS for kotlin
 	        java8 - Java 8 native JSR310
 	        threetenbp - Threetenbp
 
+	collectionType
+	    Option. Collection type to use
+	        array - kotlin.Array
+	        list - kotlin.collections.List
+
 Back to the [generators list](README.md)

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

@@ -31,9 +31,11 @@ import java.util.Map;
 public class KotlinClientCodegen extends AbstractKotlinCodegen {
 
     public static final String DATE_LIBRARY = "dateLibrary";
+    public static final String COLLECTION_TYPE = "collectionType";
     private static final Logger LOGGER = LoggerFactory.getLogger(KotlinClientCodegen.class);
 
     protected String dateLibrary = DateLibrary.JAVA8.value;
+    protected String collectionType = CollectionType.ARRAY.value;
 
     public enum DateLibrary {
         STRING("string"),
@@ -47,6 +49,17 @@ public class KotlinClientCodegen extends AbstractKotlinCodegen {
         }
     }
 
+    public enum CollectionType {
+        ARRAY("array"),
+        LIST("list");
+
+        public final String value;
+
+        CollectionType(String value) {
+            this.value = value;
+        }
+    }
+
     /**
      * Constructs an instance of `KotlinClientCodegen`.
      */
@@ -74,6 +87,13 @@ public class KotlinClientCodegen extends AbstractKotlinCodegen {
         dateOptions.put(DateLibrary.JAVA8.value, "Java 8 native JSR310");
         dateLibrary.setEnum(dateOptions);
         cliOptions.add(dateLibrary);
+
+        CliOption collectionType = new CliOption(COLLECTION_TYPE, "Option. Collection type to use");
+        Map<String, String> collectionOptions = new HashMap<>();
+        collectionOptions.put(CollectionType.ARRAY.value, "kotlin.Array");
+        collectionOptions.put(CollectionType.LIST.value, "kotlin.collections.List");
+        collectionType.setEnum(collectionOptions);
+        cliOptions.add(collectionType);
     }
 
     public CodegenType getTag() {
@@ -92,6 +112,10 @@ public class KotlinClientCodegen extends AbstractKotlinCodegen {
         this.dateLibrary = library;
     }
 
+    public void setCollectionType(String collectionType) {
+        this.collectionType = collectionType;
+    }
+
     @Override
     public void processOpts() {
         super.processOpts();
@@ -116,6 +140,15 @@ public class KotlinClientCodegen extends AbstractKotlinCodegen {
             additionalProperties.put(DateLibrary.JAVA8.value, true);
         }
 
+        if (additionalProperties.containsKey(COLLECTION_TYPE)) {
+            setCollectionType(additionalProperties.get(COLLECTION_TYPE).toString());
+        }
+
+        if (CollectionType.LIST.value.equals(collectionType)) {
+            typeMapping.put("array", "kotlin.collections.List");
+            typeMapping.put("list", "kotlin.collections.List");
+        }
+
         supportingFiles.add(new SupportingFile("README.mustache", "", "README.md"));
         supportingFiles.add(new SupportingFile("build.gradle.mustache", "", "build.gradle"));
         supportingFiles.add(new SupportingFile("settings.gradle.mustache", "", "settings.gradle"));

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

@@ -199,6 +199,33 @@ public class KotlinClientCodegenModelTest {
         Assert.assertTrue(property.isContainer);
     }
 
+    @Test(description = "convert a model with array property to a kotlin.collections.List")
+    public void listPropertyTest() {
+        final Schema model = getArrayTestSchema();
+
+        final KotlinClientCodegen codegen = new KotlinClientCodegen();
+        codegen.setCollectionType(KotlinClientCodegen.CollectionType.LIST.value);
+        codegen.processOpts();
+        final CodegenModel generated = codegen.fromModel("sample", model, Collections.singletonMap("sample", model));
+
+        Assert.assertEquals(generated.name, "sample");
+        Assert.assertEquals(generated.classname, "Sample");
+        Assert.assertEquals(generated.description, "a sample model");
+        Assert.assertEquals(generated.vars.size(), 2);
+
+        final CodegenProperty property = generated.vars.get(1);
+        Assert.assertEquals(property.baseName, "examples");
+        Assert.assertEquals(property.getter, "getExamples");
+        Assert.assertEquals(property.setter, "setExamples");
+        Assert.assertEquals(property.dataType, "kotlin.collections.List<kotlin.String>");
+        Assert.assertEquals(property.name, "examples");
+        Assert.assertEquals(property.defaultValue, "null");
+        Assert.assertEquals(property.baseType, "kotlin.collections.List");
+        Assert.assertEquals(property.containerType, "array");
+        Assert.assertFalse(property.required);
+        Assert.assertTrue(property.isContainer);
+    }
+
     @Test(description = "convert a model with a map property")
     public void mapPropertyTest() {
         final Schema schema = getMapSchema();