Kotlin ktor delegate pattern support

.gitignore

@@ -312,3 +312,6 @@ samples/client/jetbrains/adyen/checkout71/http/client/Apis/http-client.private.e
 
 # Generated by the run-in-docker.sh
 \?/
+
+# AI agent caches
+.junie

bin/configs/kotlin-server-ktor-delegate-pattern.yaml

@@ -0,0 +1,9 @@
+generatorName: kotlin-server
+outputDir: samples/server/petstore/kotlin-server/ktor-delegate-pattern/generated
+library: ktor
+inputSpec: modules/openapi-generator/src/test/resources/3_1/petstore.yaml
+templateDir: modules/openapi-generator/src/main/resources/kotlin-server
+additionalProperties:
+  hideGenerationTimestamp: "true"
+  serializableModel: "true"
+  delegatePattern: "true"

docs/generators/kotlin-server.md

@@ -22,6 +22,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |apiSuffix|suffix for api classes| |Api|
 |artifactId|Generated artifact id (name of jar).| |kotlin-server|
 |artifactVersion|Generated artifact's package version.| |1.0.0|
+|delegatePattern|Whether to generate the server files using the delegate pattern. This option is currently supported only when using ktor library.| |false|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', 'original', and 'bestEffortBacktick' (like 'original' but tries to wrap values in backticks before falling back to sanitizing, e.g. `name,asc` stays `name,asc` rather than becoming nameCommaAsc; useful for sort/order enums)| |original|
 |featureAutoHead|Automatically provide responses to HEAD requests for existing routes that have the GET verb defined.| |true|
 |featureCORS|Ktor by default provides an interceptor for implementing proper support for Cross-Origin Resource Sharing (CORS). See enable-cors.org.| |false|

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

@@ -100,6 +100,9 @@ public class KotlinServerCodegen extends AbstractKotlinCodegen implements BeanVa
     @Getter
     @Setter
     private boolean fixJacksonJsonTypeInfoInheritance = true;
+    @Getter
+    @Setter
+    private Boolean delegatePatternEnabled = false;
 
     /**
      * Constructs an instance of `KotlinServerCodegen`.
@@ -174,6 +177,7 @@ public KotlinServerCodegen() {
         addSwitch(Constants.OMIT_GRADLE_WRAPPER, Constants.OMIT_GRADLE_WRAPPER_DESC, omitGradleWrapper);
         addSwitch(USE_JAKARTA_EE, Constants.USE_JAKARTA_EE_DESC, useJakartaEe);
         addSwitch(Constants.FIX_JACKSON_JSON_TYPE_INFO_INHERITANCE, Constants.FIX_JACKSON_JSON_TYPE_INFO_INHERITANCE_DESC, fixJacksonJsonTypeInfoInheritance);
+        addSwitch(Constants.DELEGATE_PATTERN, Constants.DELEGATE_PATTERN_DESC, getDelegatePatternEnabled());
     }
 
     @Override
@@ -307,6 +311,17 @@ public void processOpts() {
         } else {
             additionalProperties.put(Constants.METRICS, getMetricsFeatureEnabled());
         }
+        if(isKtor()){
+            if (additionalProperties.containsKey(Constants.DELEGATE_PATTERN)) {
+                setDelegatePatternEnabled(convertPropertyToBooleanAndWriteBack(Constants.DELEGATE_PATTERN));
+            } else {
+                additionalProperties.put(Constants.DELEGATE_PATTERN, getDelegatePatternEnabled());
+            }
+            if (delegatePatternEnabled) {
+                typeMapping.put("file", "io.ktor.http.content.PartData.FileItem");
+                importMapping.put("io.ktor.http.content.PartData.FileItem", "io.ktor.http.content.PartData.FileItem");
+            }
+        }
 
         boolean generateApis = additionalProperties.containsKey(CodegenConstants.GENERATE_APIS) && (Boolean) additionalProperties.get(CodegenConstants.GENERATE_APIS);
         String packageFolder = (sourceFolder + File.separator + packageName).replace(".", File.separator);
@@ -330,9 +345,10 @@ public void processOpts() {
         if (isKtor2Or3()) {
             additionalProperties.put(Constants.IS_KTOR, true);
 
-            supportingFiles.add(new SupportingFile("AppMain.kt.mustache", packageFolder, "AppMain.kt"));
-            supportingFiles.add(new SupportingFile("Configuration.kt.mustache", packageFolder, "Configuration.kt"));
-
+            if(!delegatePatternEnabled) {
+                supportingFiles.add(new SupportingFile("AppMain.kt.mustache", packageFolder, "AppMain.kt"));
+                supportingFiles.add(new SupportingFile("Configuration.kt.mustache", packageFolder, "Configuration.kt"));
+            }
             if (generateApis && resourcesFeatureEnabled) {
                 supportingFiles.add(new SupportingFile("Paths.kt.mustache", packageFolder, "Paths.kt"));
             }
@@ -347,6 +363,16 @@ public void processOpts() {
             if (!getOmitGradleWrapper()) {
                 supportingFiles.add(new SupportingFile("gradle-wrapper.properties", "gradle" + File.separator + "wrapper", "gradle-wrapper.properties"));
             }
+            if(isKtor()){
+                supportingFiles.add(new SupportingFile("AllApis.kt.mustache", packageFolder, "AllApis.kt"));
+                if(delegatePatternEnabled){
+                    apiTemplateFiles.put("apiDelegate.mustache", "Delegate.kt");
+                    supportingFiles.add(new SupportingFile("Delegates.kt.mustache", infrastructureFolder, "Delegates.kt"));
+                    supportingFiles.add(new SupportingFile("AppDelegates.kt.mustache", infrastructureFolder, "AppDelegates.kt"));
+                    supportingFiles.add(new SupportingFile("BadParameterException.kt.mustache", infrastructureFolder, "BadParameterException.kt"));
+                    supportingFiles.add(new SupportingFile("APINotImplementedException.kt.mustache", infrastructureFolder, "APINotImplementedException.kt"));
+                }
+            }
 
         } else if (isJavalin()) {
             supportingFiles.add(new SupportingFile("Main.kt.mustache", packageFolder, "Main.kt"));
@@ -402,6 +428,8 @@ public static class Constants {
         public static final String FIX_JACKSON_JSON_TYPE_INFO_INHERITANCE_DESC = "When true (default), ensures Jackson polymorphism works correctly by: (1) always setting visible=true on @JsonTypeInfo, and (2) adding the discriminator property to child models with appropriate default values. When false, visible is only set to true if all children already define the discriminator property.";
         public static final String USE_TAGS = "useTags";
         public static final String USE_TAGS_DESC = "use tags for creating interface and controller classnames.";
+        public static final String DELEGATE_PATTERN = "delegatePattern";
+        public static final String DELEGATE_PATTERN_DESC = "Whether to generate the server files using the delegate pattern. This option is currently supported only when using ktor library.";
     }
 
     @Override