fallback for string file path in kotlin syntax

Author: Picazsoo

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

@@ -472,4 +472,42 @@ open class OpenApiGeneratorGenerateExtension(private val project: Project) {
         ignoreFileOverride.set(project.layout.projectDirectory.file(path))
     }
 
+    // ========================================================================
+    // Kotlin DSL extension functions for property setters
+    // These allow Kotlin DSL users to call .set(String) on file/directory properties
+    // ========================================================================
+
+    /**
+     * Extension function to allow setting inputSpec with a String path in Kotlin DSL.
+     * Example: inputSpec.set("$rootDir/api.yaml")
+     */
+    fun RegularFileProperty.set(path: String) {
+        if (this === inputSpec) {
+            setInputSpec(path)
+        } else if (this === configFile) {
+            setConfigFile(path)
+        } else if (this === ignoreFileOverride) {
+            setIgnoreFileOverride(path)
+        } else {
+            // Fallback for any other RegularFileProperty
+            this.set(project.layout.projectDirectory.file(path))
+        }
+    }
+
+    /**
+     * Extension function to allow setting directory properties with a String path in Kotlin DSL.
+     * Example: outputDir.set("$buildDir/generated")
+     */
+    fun DirectoryProperty.set(path: String) {
+        if (this === outputDir) {
+            setOutputDir(path)
+        } else if (this === inputSpecRootDirectory) {
+            setInputSpecRootDirectory(path)
+        } else if (this === templateDir) {
+            setTemplateDir(path)
+        } else {
+            // Fallback for any other DirectoryProperty
+            this.set(project.layout.projectDirectory.dir(path))
+        }
+    }
 }

modules/openapi-generator-gradle-plugin/src/test/kotlin/GenerateTaskDslTest.kt

@@ -718,4 +718,53 @@ paths:
         val versionFile = File(temp, "build/generated/.openapi-generator/VERSION")
         assertTrue(versionFile.exists(), "Generator should have run and produced output")
     }
+
+    @Test
+    fun `openApiGenerate should support Kotlin DSL set String syntax`() {
+        // Create a spec file
+        val specContent = """
+openapi: 3.0.0
+info:
+  title: Test API
+  version: 1.0.0
+paths:
+  /test:
+    get:
+      responses:
+        '200':
+          description: Success
+        """.trimIndent()
+        File(temp, "spec.yaml").writeText(specContent)
+
+        // Build script using Kotlin DSL with .set(String) syntax
+        val buildContents = """
+            plugins {
+                id("org.openapi.generator")
+            }
+            
+            openApiGenerate {
+                generatorName.set("kotlin")
+                inputSpec.set("${'$'}projectDir/spec.yaml")
+                outputDir.set("${'$'}buildDir/generated-kotlin")
+                apiPackage.set("org.openapitools.example.api")
+                modelPackage.set("org.openapitools.example.model")
+            }
+        """.trimIndent()
+
+        File(temp, "build.gradle.kts").writeText(buildContents)
+
+        // Run the generator
+        val result = GradleRunner.create()
+            .withProjectDir(temp)
+            .withArguments("openApiGenerate", "--stacktrace")
+            .withPluginClasspath()
+            .build()
+
+        // Verify the task succeeded
+        assertEquals(TaskOutcome.SUCCESS, result.task(":openApiGenerate")?.outcome)
+
+        // Verify output was generated
+        val versionFile = File(temp, "build/generated-kotlin/.openapi-generator/VERSION")
+        assertTrue(versionFile.exists(), "Generator should have produced output")
+    }
 }