add support for dry-run flag to Maven and Gradle plugins, fixes #15729 (#15734)

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

@@ -418,6 +418,12 @@ apply plugin: 'org.openapi.generator'
 |Boolean
 |false
 |Defines whether the output directory should be cleaned up before generating the output.
+
+|dryRun
+|Boolean
+|false
+|Defines whether the generator should run in dry-run mode. In dry-run mode no files are written and a summary about
+file states is output.
 |===
 
 [NOTE]

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

@@ -149,6 +149,7 @@ class OpenApiGeneratorPlugin : Plugin<Project> {
                     generateAliasAsModel.set(generate.generateAliasAsModel)
                     engine.set(generate.engine)
                     cleanupOutput.set(generate.cleanupOutput)
+                    dryRun.set(generate.dryRun)
                 }
             }
         }

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

@@ -359,6 +359,11 @@ open class OpenApiGeneratorGenerateExtension(project: Project) {
      */
     val cleanupOutput = project.objects.property<Boolean>()
 
+    /**
+     * Defines whether the generator should run in dry-run mode.
+     */
+    val dryRun = project.objects.property<Boolean>()
+
     init {
         applyDefaults()
     }
@@ -381,5 +386,6 @@ open class OpenApiGeneratorGenerateExtension(project: Project) {
         skipValidateSpec.set(false)
         generateAliasAsModel.set(false)
         cleanupOutput.set(false)
+        dryRun.set(false)
     }
 }

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

@@ -521,6 +521,13 @@ open class GenerateTask : DefaultTask() {
     @Input
     val cleanupOutput = project.objects.property<Boolean>()
 
+    /**
+     * Defines whether the generator should run in dry-run mode.
+     */
+    @Optional
+    @Input
+    val dryRun = project.objects.property<Boolean>()
+
     private fun <T : Any?> Property<T>.ifNotEmpty(block: Property<T>.(T) -> Unit) {
         if (isPresent) {
             val item: T? = get()
@@ -822,6 +829,11 @@ open class GenerateTask : DefaultTask() {
                 }
             }
 
+            var dryRunSetting = false
+            dryRun.ifNotEmpty { setting ->
+                dryRunSetting = setting
+            }
+
             val clientOptInput = configurator.toClientOptInput()
             val codegenConfig = clientOptInput.config
 
@@ -838,7 +850,7 @@ open class GenerateTask : DefaultTask() {
                 val out = services.get(StyledTextOutputFactory::class.java).create("openapi")
                 out.withStyle(StyledTextOutput.Style.Success)
 
-                DefaultGenerator().opts(clientOptInput).generate()
+                DefaultGenerator(dryRunSetting).opts(clientOptInput).generate()
 
                 out.println("Successfully generated code to ${outputDir.get()}")
             } catch (e: RuntimeException) {

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

@@ -458,4 +458,45 @@ class GenerateTaskDslTest : TestBase() {
         assertEquals(TaskOutcome.FAILED, result.task(":openApiGenerate")?.outcome,
             "Expected a failed run, but found ${result.task(":openApiGenerate")?.outcome}")
     }
+
+    @Test
+    fun `openapiGenerate should set dryRun flag`() {
+        // Arrange
+        val projectFiles = mapOf(
+            "spec.yaml" to javaClass.classLoader.getResourceAsStream("specs/petstore-v3.0.yaml")
+        )
+        withProject(
+            """
+        plugins {
+          id 'org.openapi.generator'
+        }
+        openApiGenerate {
+            generatorName = "kotlin"
+            inputSpec = file("spec.yaml").absolutePath
+            outputDir = file("build/kotlin").absolutePath
+            apiPackage = "org.openapitools.example.api"
+            invokerPackage = "org.openapitools.example.invoker"
+            modelPackage = "org.openapitools.example.model"
+            configOptions = [
+                    dateLibrary: "java8"
+            ]
+            dryRun = true
+        }
+    """.trimIndent(),
+            projectFiles
+        )
+
+        // Act
+        val result = GradleRunner.create()
+            .withProjectDir(temp)
+            .withArguments("openApiGenerate")
+            .withPluginClasspath()
+            .build()
+
+        // Assert
+        assertTrue(
+            result.output.contains("Dry Run Results:"),
+            "Dry run results message is missing."
+        )
+    }
 }

modules/openapi-generator-maven-plugin/README.md

@@ -107,6 +107,7 @@ mvn clean compile
 | `skipIfSpecIsUnchanged` |  `codegen.skipIfSpecIsUnchanged` | Skip the execution if the source file is older than the output folder (`false` by default. Can also be set globally through the `codegen.skipIfSpecIsUnchanged` property)
 | `addCompileSourceRoot` |  `openapi.generator.maven.plugin.addCompileSourceRoot` | Add the output directory to the project as a source root, so that the generated java types are compiled and included in the project artifact (`true` by default). Mutually exclusive with `addTestCompileSourceRoot`.
 | `addTestCompileSourceRoot` |  `openapi.generator.maven.plugin.addTestCompileSourceRoot` | Add the output directory to the project as a test source root, so that the generated java types are compiled only for the test classpath of the project (`false` by default). Mutually exclusive with `addCompileSourceRoot`.
+| `dryRun` | `openapi.generator.maven.plugin.dryRun` | Defines whether the generator should run in dry-run mode. In dry-run mode no files are written and a summary about file states is output ( `false` by default).
 | `environmentVariables` | N/A | deprecated. Use globalProperties instead.
 | `globalProperties` | N/A | A **map** of items conceptually similar to "environment variables" or "system properties". These are available to all aspects of the generation flow. See [Global Properties](https://openapi-generator.tech/docs/globals/) for list of available properties.
 | `configHelp` |  `codegen.configHelp` | dumps the configuration help for the specified library (generates no sources)

modules/openapi-generator-maven-plugin/src/main/java/org/openapitools/codegen/plugin/CodeGenMojo.java

@@ -460,6 +460,9 @@ public class CodeGenMojo extends AbstractMojo {
     @Parameter(defaultValue = "false", property = "openapi.generator.maven.plugin.addTestCompileSourceRoot")
     private boolean addTestCompileSourceRoot = false;
 
+    @Parameter(defaultValue = "false", property = "openapi.generator.maven.plugin.dryRun")
+    private Boolean dryRun = false;
+
     // TODO: Rename to global properties in version 5.1
     @Parameter
     protected Map<String, String> environmentVariables = new HashMap<>();
@@ -867,7 +870,7 @@ public class CodeGenMojo extends AbstractMojo {
                 return;
             }
             adjustAdditionalProperties(config);
-            new DefaultGenerator().opts(input).generate();
+            new DefaultGenerator(dryRun).opts(input).generate();
 
             if (buildContext != null) {
                 buildContext.refresh(new File(getCompileSourceRoot()));