[kotlin-client][kotlin-server] Feature/kotlin data class serial version uid (#4021)

* feat: add companion object to data classes if the implement the interface java.io.Serializable

* style: format template file

* style: adapt to project's original code style

* fix: add missing imports

* style: reverted mustache template to original styling

* test: generate additional samples for kotlin-springboot-reactive and kotlin-springboot

* docs: name full qualified classname of interface java.io.Serializable to prevent confusion with kotlinx.serialization

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

@@ -248,6 +248,9 @@ public class CodegenConstants {
     public static final String CASE_INSENSITIVE_RESPONSE_HEADERS = "caseInsensitiveResponseHeaders";
     public static final String CASE_INSENSITIVE_RESPONSE_HEADERS_DESC = "Make API response's headers case-insensitive";
 
+    public static final String NEEDS_DATACLASS_BODY = "needsDataClassBody";
+    public static final String NEEDS_DATACLASS_BODY_DESC = "Specifies if the kotlin data class needs a body with curly braces or not.";
+
     // Not user-configurable. System provided for use in templates.
 
     public static final String GENERATE_APIS = "generateApis";

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

@@ -24,6 +24,7 @@ import org.apache.commons.lang3.StringUtils;
 import org.openapitools.codegen.CliOption;
 import org.openapitools.codegen.CodegenConfig;
 import org.openapitools.codegen.CodegenConstants;
+import org.openapitools.codegen.CodegenModel;
 import org.openapitools.codegen.DefaultCodegen;
 import org.openapitools.codegen.utils.ModelUtils;
 import org.slf4j.Logger;
@@ -31,12 +32,14 @@ import org.slf4j.LoggerFactory;
 
 import java.io.File;
 import java.util.*;
+import java.util.stream.Collectors;
 
 import static org.openapitools.codegen.utils.StringUtils.*;
 
 public abstract class AbstractKotlinCodegen extends DefaultCodegen implements CodegenConfig {
 
     public static final String SERIALIZATION_LIBRARY_DESC = "What serialization library to use: 'moshi' (default), or 'gson'";
+
     public enum SERIALIZATION_LIBRARY_TYPE {moshi, gson}
 
     private static final Logger LOGGER = LoggerFactory.getLogger(AbstractKotlinCodegen.class);
@@ -53,8 +56,9 @@ public abstract class AbstractKotlinCodegen extends DefaultCodegen implements Co
     protected String apiDocPath = "docs/";
     protected String modelDocPath = "docs/";
     protected boolean parcelizeModels = false;
-
     protected boolean serializableModel = false;
+    protected boolean needsDataClassBody = false;
+    protected boolean hasEnums = false;
 
     protected CodegenConstants.ENUM_PROPERTY_NAMING_TYPE enumPropertyNaming = CodegenConstants.ENUM_PROPERTY_NAMING_TYPE.camelCase;
     protected SERIALIZATION_LIBRARY_TYPE serializationLibrary = SERIALIZATION_LIBRARY_TYPE.moshi;
@@ -426,6 +430,7 @@ public abstract class AbstractKotlinCodegen extends DefaultCodegen implements Co
             additionalProperties.put(CodegenConstants.PARCELIZE_MODELS, parcelizeModels);
         }
 
+        additionalProperties.put(CodegenConstants.NEEDS_DATACLASS_BODY, this.hasEnums || serializableModel);
         additionalProperties.put(CodegenConstants.API_PACKAGE, apiPackage());
         additionalProperties.put(CodegenConstants.MODEL_PACKAGE, modelPackage());
 
@@ -476,6 +481,15 @@ public abstract class AbstractKotlinCodegen extends DefaultCodegen implements Co
     public void setSerializableModel(boolean serializableModel) {
         this.serializableModel = serializableModel;
     }
+
+    public boolean isNeedsDataClassBody() {
+        return needsDataClassBody;
+    }
+
+    public void setNeedsDataClassBody(boolean needsDataClassBody) {
+        this.needsDataClassBody = needsDataClassBody;
+    }
+
     /**
      * Return the sanitized variable name for enum
      *
@@ -746,6 +760,15 @@ public abstract class AbstractKotlinCodegen extends DefaultCodegen implements Co
         return imports;
     }
 
+    @Override
+    public CodegenModel fromModel(String name, Schema schema) {
+        CodegenModel m = super.fromModel(name, schema);
+        m.optionalVars = m.optionalVars.stream().distinct().collect(Collectors.toList());
+        m.allVars.stream().filter(p -> !m.vars.contains(p)).forEach(p -> p.isInherited = true);
+        this.hasEnums = m.hasEnums;
+        return m;
+    }
+
     @Override
     public String toEnumValue(String value, String datatype) {
         if ("kotlin.Int".equals(datatype) || "kotlin.Long".equals(datatype)) {

modules/openapi-generator/src/main/resources/kotlin-client/data_class.mustache

@@ -37,8 +37,12 @@ data class {{classname}} (
 ) {{^serializableModel}}{{#parcelizeModels}} : Parcelable{{/parcelizeModels}}{{/serializableModel}}
 {{^parcelizeModels}}{{#serializableModel}}: Serializable {{/serializableModel}}{{/parcelizeModels}}
 {{#parcelizeModels}}{{#serializableModel}} : Parcelable, Serializable {{/serializableModel}}{{/parcelizeModels}}
-{{#hasEnums}}
-{
+{{#needsDataClassBody}}{{=<% %>=}}{<%={{ }}=%>{{/needsDataClassBody}}
+{{#serializableModel}}
+	companion object {
+		private const val serialVersionUID: Long = 123
+	}
+{{/serializableModel}}{{#hasEnums}}
 {{#vars}}{{#isEnum}}
     /**
     * {{{description}}}
@@ -65,5 +69,4 @@ data class {{classname}} (
     {{/multiplatform}}
     }
 {{/isEnum}}{{/vars}}
-}
-{{/hasEnums}}
+{{/hasEnums}}{{#needsDataClassBody}}{{=<% %>=}}}<%={{ }}=%>{{/needsDataClassBody}}

modules/openapi-generator/src/main/resources/kotlin-server/data_class.mustache

@@ -21,11 +21,15 @@ data class {{classname}} (
 {{/-last}}{{/requiredVars}}{{#hasRequired}}{{#hasOptional}},
 {{/hasOptional}}{{/hasRequired}}{{#optionalVars}}{{>data_class_opt_var}}{{^-last}},
 {{/-last}}{{/optionalVars}}
-) {{^serializableModel}}{{#parcelizeModels}} : Parcelable{{/parcelizeModels}}{{/serializableModel}}
-{{^parcelizeModels}}{{#serializableModel}}: Serializable {{/serializableModel}}{{/parcelizeModels}}
-{{#parcelizeModels}}{{#serializableModel}} : Parcelable, Serializable {{/serializableModel}}{{/parcelizeModels}}
-{
-{{#hasEnums}}{{#vars}}{{#isEnum}}
+) {{^serializableModel}}{{#parcelizeModels}} : Parcelable{{/parcelizeModels}}{{/serializableModel}}{{^parcelizeModels}}{{#serializableModel}}: Serializable {{/serializableModel}}{{/parcelizeModels}}{{#parcelizeModels}}{{#serializableModel}} : Parcelable, Serializable {{/serializableModel}}{{/parcelizeModels}}
+{{#needsDataClassBody}}{{=<% %>=}}{<%={{ }}=%>{{/needsDataClassBody}}
+{{#serializableModel}}
+	companion object {
+		private const val serialVersionUID: Long = 123
+	}
+{{/serializableModel}}
+{{#hasEnums}}
+	{{#vars}}{{#isEnum}}
     /**
     * {{{description}}}
     * Values: {{#allowableValues}}{{#enumVars}}{{&name}}{{^-last}},{{/-last}}{{/enumVars}}{{/allowableValues}}
@@ -35,5 +39,4 @@ data class {{classname}} (
         {{&name}}({{{value}}}){{^-last}},{{/-last}}{{#-last}};{{/-last}}
     {{/enumVars}}{{/allowableValues}}
     }
-{{/isEnum}}{{/vars}}{{/hasEnums}}
-}
+{{/isEnum}}{{/vars}}{{/hasEnums}}{{#needsDataClassBody}}{{=<% %>=}}}<%={{ }}=%>{{/needsDataClassBody}}