Kotlin Facet: Filter out API versions exceeding library version

Also drop version validator as it's not needed anymore
 #KT-17847 Fixed

idea/src/org/jetbrains/kotlin/idea/compiler/configuration/KotlinCompilerConfigurableTab.java

@@ -136,7 +136,7 @@ public class KotlinCompilerConfigurableTab implements SearchableConfigurable, Co
                     new ActionListener() {
                         @Override
                         public void actionPerformed(ActionEvent e) {
-                            restrictAPIVersions();
+                            restrictAPIVersions(getSelectedLanguageVersion());
                         }
                     }
             );
@@ -300,27 +300,22 @@ public class KotlinCompilerConfigurableTab implements SearchableConfigurable, Co
     }
 
     @SuppressWarnings("unchecked")
-    public void restrictAPIVersions() {
+    public void restrictAPIVersions(LanguageVersion upperBound) {
         ApiVersion selectedAPIVersion = getSelectedAPIVersion();
-        final LanguageVersion selectedLanguageVersion = getSelectedLanguageVersion();
         List<ApiVersion> permittedAPIVersions = ArraysKt.mapNotNull(
                 LanguageVersion.values(),
-                new Function1<LanguageVersion, ApiVersion>() {
-                    @Override
-                    public ApiVersion invoke(LanguageVersion version) {
-                        return VersionComparatorUtil.compare(version.getVersionString(), selectedLanguageVersion.getVersionString()) <= 0
-                               ? ApiVersion.createByLanguageVersion(version)
-                               : null;
-                    }
-                }
+                version -> VersionComparatorUtil.compare(version.getVersionString(), upperBound.getVersionString()) <= 0 &&
+                           VersionComparatorUtil.compare(version.getVersionString(), upperBound.getVersionString()) <= 0
+                       ? ApiVersion.createByLanguageVersion(version)
+                       : null
         );
         apiVersionComboBox.setModel(
                 new DefaultComboBoxModel(permittedAPIVersions.toArray())
         );
         apiVersionComboBox.setSelectedItem(
-                VersionComparatorUtil.compare(selectedAPIVersion.getVersionString(), selectedLanguageVersion.getVersionString()) <= 0
+                VersionComparatorUtil.compare(selectedAPIVersion.getVersionString(), upperBound.getVersionString()) <= 0
                 ? selectedAPIVersion
-                : selectedLanguageVersion
+                : upperBound
         );
     }
 
@@ -424,7 +419,7 @@ public class KotlinCompilerConfigurableTab implements SearchableConfigurable, Co
     }
 
     @NotNull
-    private LanguageVersion getSelectedLanguageVersion() {
+    public LanguageVersion getSelectedLanguageVersion() {
         Object item = languageVersionComboBox.getSelectedItem();
         return item != null ? (LanguageVersion) item : LanguageVersion.LATEST_STABLE;
     }
@@ -520,7 +515,7 @@ public class KotlinCompilerConfigurableTab implements SearchableConfigurable, Co
         reportWarningsCheckBox.setSelected(!commonCompilerArguments.suppressWarnings);
         languageVersionComboBox.setSelectedItem(getLanguageVersionOrDefault(commonCompilerArguments.languageVersion));
         apiVersionComboBox.setSelectedItem(getApiVersionOrDefault(commonCompilerArguments.apiVersion));
-        restrictAPIVersions();
+        restrictAPIVersions(getSelectedLanguageVersion());
         coroutineSupportComboBox.setSelectedItem(CoroutineSupport.byCompilerArguments(commonCompilerArguments));
         additionalArgsOptionsField.setText(compilerSettings.additionalArguments);
         scriptTemplatesField.setText(compilerSettings.scriptTemplates);

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

@@ -147,23 +147,6 @@ class KotlinFacetEditorGeneralTab(
             get() = targetPlatformComboBox.selectedItem as TargetPlatformKind<*>?
     }
 
-    inner class VersionValidator : FacetEditorValidator() {
-        override fun check(): ValidationResult {
-            val apiLevel = editor.compilerConfigurable.apiVersionComboBox.selectedItem as? ApiVersion?
-                           ?: return ValidationResult.OK
-            val languageLevel = editor.compilerConfigurable.languageVersionComboBox.selectedItem as? LanguageVersion?
-                                ?: return ValidationResult.OK
-            val targetPlatform = editor.targetPlatformComboBox.selectedItem as TargetPlatformKind<*>?
-            val libraryLevel = getLibraryLanguageLevel(editorContext.module, editorContext.rootModel, targetPlatform)
-
-            val apiLevelVersion = LanguageVersion.fromVersionString(apiLevel.versionString) ?: return ValidationResult.OK
-            if (languageLevel < apiLevelVersion || libraryLevel < apiLevelVersion) {
-                return ValidationResult("Language version/Runtime version may not be less than API version", null)
-            }
-            return ValidationResult.OK
-        }
-    }
-
     inner class ArgumentConsistencyValidator : FacetEditorValidator() {
         override fun check(): ValidationResult {
             val platform = editor.targetPlatformComboBox.selectedItem as TargetPlatformKind<*>? ?: return ValidationResult.OK
@@ -221,7 +204,6 @@ class KotlinFacetEditorGeneralTab(
     val editor = EditorComponent(editorContext.project, configuration)
 
     private val libraryValidator: FrameworkLibraryValidator
-    private val versionValidator = VersionValidator()
     private val coroutineValidator = ArgumentConsistencyValidator()
 
     private var enableValidation = false
@@ -234,7 +216,6 @@ class KotlinFacetEditorGeneralTab(
         ) { editor.targetPlatformComboBox.selectedItem as TargetPlatformKind<*> }
 
         validatorsManager.registerValidator(libraryValidator)
-        validatorsManager.registerValidator(versionValidator)
         validatorsManager.registerValidator(coroutineValidator)
 
         with(editor.compilerConfigurable) {
@@ -258,6 +239,15 @@ class KotlinFacetEditorGeneralTab(
         editor.updateCompilerConfigurable()
     }
 
+    private fun restrictAPIVersions() {
+        with(editor.compilerConfigurable) {
+            val targetPlatform = editor.targetPlatformComboBox.selectedItem as TargetPlatformKind<*>?
+            val libraryLevel = getLibraryLanguageLevel(editorContext.module, editorContext.rootModel, targetPlatform)
+            val versionUpperBound = minOf(selectedLanguageVersion, libraryLevel)
+            restrictAPIVersions(versionUpperBound)
+        }
+    }
+
     private fun JTextField.validateOnChange() {
         document.addDocumentListener(
                 object : DocumentAdapter() {