Kotlin Facet: Track configuration version

idea/idea-jps-common/src/org/jetbrains/kotlin/config/KotlinFacetSettings.kt

@@ -76,6 +76,12 @@ class KotlinCompilerInfo {
 }
 
 class KotlinFacetSettings {
+    companion object {
+        // Increment this when making serialization-incompatible changes to configuration data
+        val CURRENT_VERSION = 1
+        val DEFAULT_VERSION = 0
+    }
+
     var versionInfo = KotlinVersionInfo()
     var compilerInfo = KotlinCompilerInfo()
 }

idea/src/org/jetbrains/kotlin/idea/facet/KotlinFacetConfiguration.kt

@@ -20,36 +20,46 @@ import com.intellij.facet.FacetConfiguration
 import com.intellij.facet.ui.FacetEditorContext
 import com.intellij.facet.ui.FacetEditorTab
 import com.intellij.facet.ui.FacetValidatorsManager
-import com.intellij.openapi.components.PersistentStateComponent
+import com.intellij.util.xmlb.XmlSerializer
+import org.jdom.DataConversionException
 import org.jdom.Element
 import org.jetbrains.kotlin.config.KotlinFacetSettings
 
-class KotlinFacetConfiguration : FacetConfiguration, PersistentStateComponent<KotlinFacetSettings> {
-    private var settings = KotlinFacetSettings()
+class KotlinFacetConfiguration : FacetConfiguration {
+    var settings = KotlinFacetSettings()
+        private set
 
     @Suppress("OverridingDeprecatedMember")
-    override fun readExternal(element: Element?) {
-
+    override fun readExternal(element: Element) {
+        val version =
+                try {
+                    element.getAttribute("version")?.intValue
+                }
+                catch(e: DataConversionException) {
+                    null
+                } ?: KotlinFacetSettings.DEFAULT_VERSION
+        // Reset facet configuration if versions don't match
+        if (version == KotlinFacetSettings.CURRENT_VERSION) {
+            XmlSerializer.deserializeInto(settings, element)
+        }
+        else {
+            settings = KotlinFacetSettings()
+        }
     }
 
     @Suppress("OverridingDeprecatedMember")
-    override fun writeExternal(element: Element?) {
-
+    override fun writeExternal(element: Element) {
+        element.setAttribute("version", KotlinFacetSettings.CURRENT_VERSION.toString())
+        XmlSerializer.serializeInto(settings, element)
     }
 
-    override fun loadState(state: KotlinFacetSettings) {
-        this.settings = state
-    }
-
-    override fun getState() = settings
-
     override fun createEditorTabs(
             editorContext: FacetEditorContext,
             validatorsManager: FacetValidatorsManager
     ): Array<FacetEditorTab> {
-        state.initializeIfNeeded(editorContext.module, editorContext.rootModel)
+        settings.initializeIfNeeded(editorContext.module, editorContext.rootModel)
 
-        val compilerTab = KotlinFacetEditorCompilerTab(state.compilerInfo, editorContext)
+        val compilerTab = KotlinFacetEditorCompilerTab(settings.compilerInfo, editorContext)
         val generalTab = KotlinFacetEditorGeneralTab(this, editorContext, validatorsManager, compilerTab)
         val tabs = arrayListOf(generalTab, compilerTab)
         KotlinFacetConfigurationExtension.EP_NAME.extensions.flatMapTo(tabs) { it.createEditorTabs(editorContext, validatorsManager) }

idea/src/org/jetbrains/kotlin/idea/facet/KotlinFacetEditorGeneralTab.kt

@@ -105,7 +105,7 @@ class KotlinFacetEditorGeneralTab(
     }
 
     override fun isModified(): Boolean {
-        return with(configuration.state.versionInfo) {
+        return with(configuration.settings.versionInfo) {
             languageVersionComboBox.selectedItem != languageLevel
             || targetPlatformComboBox.selectedItem != targetPlatformKind
             || apiVersionComboBox.selectedItem != apiLevel
@@ -113,7 +113,7 @@ class KotlinFacetEditorGeneralTab(
     }
 
     override fun reset() {
-        with(configuration.state.versionInfo) {
+        with(configuration.settings.versionInfo) {
             languageVersionComboBox.selectedItem = languageLevel
             targetPlatformComboBox.selectedItem = targetPlatformKind
             apiVersionComboBox.selectedItem = apiLevel
@@ -121,7 +121,7 @@ class KotlinFacetEditorGeneralTab(
     }
 
     override fun apply() {
-        with(configuration.state.versionInfo) {
+        with(configuration.settings.versionInfo) {
             languageLevel = languageVersionComboBox.selectedItem as LanguageVersion?
             targetPlatformKind = targetPlatformComboBox.selectedItem as TargetPlatformKind<*>?
             apiLevel = apiVersionComboBox.selectedItem as LanguageVersion?

idea/src/org/jetbrains/kotlin/idea/facet/KotlinFacetSettingsProviderImpl.kt

@@ -22,7 +22,7 @@ import org.jetbrains.kotlin.config.KotlinFacetSettingsProvider
 
 class KotlinFacetSettingsProviderImpl : KotlinFacetSettingsProvider {
     override fun getSettings(module: Module): KotlinFacetSettings {
-        val settings = KotlinFacet.get(module)?.configuration?.state ?: KotlinFacetSettings()
+        val settings = KotlinFacet.get(module)?.configuration?.settings ?: KotlinFacetSettings()
         settings.initializeIfNeeded(module, null)
         return settings
     }