[Enhancement] [Gradle Plugin] Allow templates from classpath (#14909)

* [Enhancement] [Gradle Plugin] Allow templates from classpath

* Adding missing argument binding.

modules/openapi-generator-gradle-plugin/README.adoc

@@ -174,6 +174,10 @@ apply plugin: 'org.openapi.generator'
 |None
 |The template directory holding a custom template.
 
+|templateResourcePath
+|String
+|Directory with mustache templates via resource path. This option will overwrite any option defined in `templateDir`
+
 |auth
 |String
 |None

modules/openapi-generator-gradle-plugin/src/main/kotlin/org/openapitools/generator/gradle/plugin/OpenApiGeneratorPlugin.kt

@@ -100,6 +100,7 @@ class OpenApiGeneratorPlugin : Plugin<Project> {
                     inputSpecRootDirectory.set(generate.inputSpecRootDirectory)
                     remoteInputSpec.set(generate.remoteInputSpec)
                     templateDir.set(generate.templateDir)
+                    templateResourcePath.set(generate.templateResourcePath)
                     auth.set(generate.auth)
                     globalProperties.set(generate.globalProperties)
                     configFile.set(generate.configFile)

modules/openapi-generator-gradle-plugin/src/main/kotlin/org/openapitools/generator/gradle/plugin/extensions/OpenApiGeneratorGenerateExtension.kt

@@ -69,6 +69,11 @@ open class OpenApiGeneratorGenerateExtension(project: Project) {
      */
     val templateDir = project.objects.property<String?>()
 
+    /**
+     * The template location (which may be a directory or a classpath location) holding custom templates.
+     */
+    val templateResourcePath = project.objects.property<String?>()
+
     /**
      * Adds authorization headers when fetching the OpenAPI definitions remotely.
      * Pass in a URL-encoded string of name:header with a comma separating multiple values

modules/openapi-generator-gradle-plugin/src/main/kotlin/org/openapitools/generator/gradle/plugin/tasks/GenerateTask.kt

@@ -133,6 +133,13 @@ open class GenerateTask @Inject constructor(private val objectFactory: ObjectFac
     @PathSensitive(PathSensitivity.RELATIVE)
     val templateDir = project.objects.property<String?>()
 
+    /**
+     * Resource path containing template files.
+     */
+    @Optional
+    @Input
+    val templateResourcePath = project.objects.property<String?>()
+
     /**
      * Adds authorization headers when fetching the OpenAPI definitions remotely.
      * Pass in a URL-encoded string of name:header with a comma separating multiple values
@@ -707,6 +714,13 @@ open class GenerateTask @Inject constructor(private val objectFactory: ObjectFac
                 configurator.setTemplateDir(value)
             }
 
+            templateResourcePath.ifNotEmpty { value ->
+                templateDir.ifNotEmpty {
+                    logger.warn("Both templateDir and templateResourcePath were configured. templateResourcePath overwrites templateDir.")
+                }
+                configurator.setTemplateDir(value)
+            }
+
             packageName.ifNotEmpty { value ->
                 configurator.setPackageName(value)
             }