Enabled configuration via Gradle build file, and improved documentation.

Author: erikvanderwerf

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

@@ -98,6 +98,7 @@ class OpenApiGeneratorPlugin : Plugin<Project> {
                     outputDir.set(generate.outputDir)
                     inputSpec.set(generate.inputSpec)
                     inputSpecRootDirectory.set(generate.inputSpecRootDirectory)
+                    inputSpecRootDirectorySkipMerge.set(generate.inputSpecRootDirectorySkipMerge)
                     remoteInputSpec.set(generate.remoteInputSpec)
                     templateDir.set(generate.templateDir)
                     templateResourcePath.set(generate.templateResourcePath)

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

@@ -51,14 +51,28 @@ open class OpenApiGeneratorGenerateExtension(project: Project) {
 
     /**
      * The Open API 2.0/3.x specification location.
+     *
+     * Be default, Gradle will treat the openApiGenerate task as up-to-date based only on this file, regardless of
+     * changes to any $ref referenced files. Use the `inputSpecRootDirectory` property to have Gradle track changes to
+     * an entire directory of spec files.
      */
     val inputSpec = project.objects.property<String>()
 
     /**
-     * Local root folder with spec files
+     * Local root folder with spec files.
+     *
+     * By default, a merged spec file will be generated based on the contents of the directory. To disable this, set the
+     * `inputSpecRootDirectorySkipMerge` property.
      */
     val inputSpecRootDirectory = project.objects.property<String>()
 
+    /**
+     * Skip bundling all spec files into a merged spec file, if true.
+     *
+     * Default false.
+     */
+    val inputSpecRootDirectorySkipMerge = project.objects.property<Boolean>()
+
     /**
      * The remote Open API 2.0/3.x specification URL location.
      */
@@ -400,6 +414,7 @@ open class OpenApiGeneratorGenerateExtension(project: Project) {
     @Suppress("MemberVisibilityCanBePrivate")
     fun applyDefaults() {
         releaseNote.set("Minor update")
+        inputSpecRootDirectorySkipMerge.set(false)
         modelNamePrefix.set("")
         modelNameSuffix.set("")
         apiNameSuffix.set("")

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

@@ -97,22 +97,29 @@ open class GenerateTask @Inject constructor(private val objectFactory: ObjectFac
 
     /**
      * The Open API 2.0/3.x specification location.
+     *
+     * Be default, Gradle will treat the openApiGenerate task as up-to-date based only on this file, regardless of
+     * changes to any $ref referenced files. Use the `inputSpecRootDirectory` property to have Gradle track changes to
+     * an entire directory of spec files.
      */
     @Optional
     @get:InputFile
     @PathSensitive(PathSensitivity.RELATIVE)
     val inputSpec = project.objects.property<String>()
 
     /**
-     * Local root folder with spec files
+     * Local root folder with spec files.
+     *
+     * By default, a merged spec file will be generated based on the contents of the directory. To disable this, set the
+     * `inputSpecRootDirectorySkipMerge` property.
      */
     @Optional
     @get:InputDirectory
     @PathSensitive(PathSensitivity.RELATIVE)
     val inputSpecRootDirectory = project.objects.property<String>();
 
     /**
-     * Skip merge spec files step
+     * Skip bundling all spec files into a merged spec file, if true.
      */
     @Input
     @Optional
@@ -623,8 +630,9 @@ open class GenerateTask @Inject constructor(private val objectFactory: ObjectFac
         }
 
         inputSpecRootDirectory.ifNotEmpty { inputSpecRootDirectoryValue ->
-            var runMergeSpec = true
-            inputSpecRootDirectorySkipMerge.ifNotEmpty { skipMergeValue -> { runMergeSpec = !skipMergeValue } }
+            val skipMerge = inputSpecRootDirectorySkipMerge.get()
+            val runMergeSpec = !skipMerge
+            System.err.println("Checking: $runMergeSpec / $inputSpecRootDirectorySkipMerge / ${inputSpecRootDirectorySkipMerge.get()} / ${inputSpecRootDirectorySkipMerge.get()::class.java}.")
             if (runMergeSpec) {
                 run {
                     resolvedInputSpec = MergedSpecBuilder(