Add quickfix to increase language level by editing build.gradle

idea/src/org/jetbrains/kotlin/idea/configuration/KotlinWithGradleConfigurator.kt

@@ -43,6 +43,7 @@ import org.jetbrains.plugins.groovy.lang.psi.GroovyPsiElementFactory
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.GrStatement
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.blocks.GrClosableBlock
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.GrApplicationStatement
+import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.GrAssignmentExpression
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.GrMethodCall
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.path.GrMethodCallExpression
 import org.jetbrains.plugins.groovy.lang.psi.api.util.GrStatementOwner
@@ -273,6 +274,22 @@ abstract class KotlinWithGradleConfigurator : KotlinProjectConfigurator {
             return kotlinBlock.parent
         }
 
+        fun changeLanguageVersion(module: Module, languageVersion: String, forTests: Boolean): PsiElement? {
+            return changeBuildGradle(module) { gradleFile ->
+                changeLanguageVersion(gradleFile, languageVersion, forTests)
+            }
+        }
+
+        fun changeLanguageVersion(gradleFile: GroovyFile, languageVersion: String, forTests: Boolean): PsiElement? {
+            val snippet = "languageVersion = \"$languageVersion\""
+            val kotlinBlock = getBlockOrCreate(gradleFile, if (forTests) "compileTestKotlin" else "compileKotlin")
+            val experimentalBlock = getBlockOrCreate(kotlinBlock, "kotlinOptions")
+            addOrReplaceExpression(experimentalBlock, snippet) { stmt ->
+                (stmt as? GrAssignmentExpression)?.lValue?.text == "languageVersion"
+            }
+            return kotlinBlock.parent
+        }
+
         private fun changeBuildGradle(module: Module, body: (GroovyFile) -> PsiElement?): PsiElement? {
             val gradleFilePath = getModuleFilePath(module)
             val gradleFile = getBuildGradleFile(module.project, gradleFilePath)

idea/src/org/jetbrains/kotlin/idea/quickfix/EnableUnsupportedFeatureFix.kt

@@ -17,8 +17,10 @@
 package org.jetbrains.kotlin.idea.quickfix
 
 import com.intellij.openapi.editor.Editor
+import com.intellij.openapi.fileEditor.OpenFileDescriptor
 import com.intellij.openapi.module.ModuleUtilCore
 import com.intellij.openapi.project.Project
+import com.intellij.openapi.roots.ModuleRootManager
 import com.intellij.openapi.roots.ModuleRootModificationUtil
 import com.intellij.openapi.roots.ex.ProjectRootManagerEx
 import com.intellij.psi.PsiElement
@@ -27,6 +29,7 @@ import org.jetbrains.kotlin.diagnostics.Diagnostic
 import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.idea.KotlinPluginUtil
 import org.jetbrains.kotlin.idea.compiler.configuration.KotlinCommonCompilerArgumentsHolder
+import org.jetbrains.kotlin.idea.configuration.KotlinWithGradleConfigurator
 import org.jetbrains.kotlin.idea.facet.KotlinFacet
 import org.jetbrains.kotlin.psi.KtFile
 
@@ -41,6 +44,15 @@ sealed class EnableUnsupportedFeatureFix(
 
         override fun invoke(project: Project, editor: Editor?, file: KtFile) {
             val module = ModuleUtilCore.findModuleForPsiElement(file) ?: return
+            if (KotlinPluginUtil.isGradleModule(module)) {
+                val forTests = ModuleRootManager.getInstance(module).fileIndex.isInTestSourceContent(file.virtualFile)
+                val element = KotlinWithGradleConfigurator.changeLanguageVersion(module, targetVersion.versionString, forTests)
+                element?.let {
+                    OpenFileDescriptor(project, it.containingFile.virtualFile, it.textRange.startOffset).navigate(true)
+                }
+                return
+            }
+
             val facetSettings = KotlinFacet.get(module)?.configuration?.settings ?: return
             ModuleRootModificationUtil.updateModel(module) {
                 with(facetSettings.versionInfo) {
@@ -69,9 +81,11 @@ sealed class EnableUnsupportedFeatureFix(
         override fun createAction(diagnostic: Diagnostic): EnableUnsupportedFeatureFix? {
             val targetVersion = Errors.UNSUPPORTED_FEATURE.cast(diagnostic).a.sinceVersion ?: return null
             val module = ModuleUtilCore.findModuleForPsiElement(diagnostic.psiElement) ?: return null
-            if (KotlinPluginUtil.isGradleModule(module) || KotlinPluginUtil.isMavenModule(module)) return null
-            val facetSettings = KotlinFacet.get(module)?.configuration?.settings
-            if (facetSettings == null || facetSettings.useProjectSettings) return InProject(diagnostic.psiElement, targetVersion)
+            if (KotlinPluginUtil.isMavenModule(module)) return null
+            if (!KotlinPluginUtil.isGradleModule(module)) {
+                val facetSettings = KotlinFacet.get(module)?.configuration?.settings
+                if (facetSettings == null || facetSettings.useProjectSettings) return InProject(diagnostic.psiElement, targetVersion)
+            }
             return InModule(diagnostic.psiElement, targetVersion)
         }
     }

idea/tests/org/jetbrains/kotlin/gradle/KotlinWithGradleConfiguratorTest.kt

@@ -58,4 +58,41 @@ class KotlinWithGradleConfiguratorTest : LightCodeInsightFixtureTestCase() {
                   |}
                   |""".trimMargin("|"))
     }
+
+    fun testAddLanguageVersion() {
+        val buildGradle = myFixture.configureByText("build.gradle", "apply plugin: 'kotlin'\n") as GroovyFile
+        myFixture.project.executeWriteCommand("") {
+            KotlinWithGradleConfigurator.changeLanguageVersion(buildGradle, "1.1", false)
+        }
+        myFixture.checkResult(
+                """apply plugin: 'kotlin'
+                  |compileKotlin {
+                  |    kotlinOptions {
+                  |        languageVersion = "1.1"
+                  |    }
+                  |}
+                  |""".trimMargin("|"))
+    }
+
+    fun testChangeLanguageVersion() {
+        val buildGradle = myFixture.configureByText("build.gradle",
+               """apply plugin: 'kotlin'
+                  |compileKotlin {
+                  |    kotlinOptions {
+                  |        languageVersion = "1.0"
+                  |    }
+                  |}
+                  |""".trimMargin("|")) as GroovyFile
+        myFixture.project.executeWriteCommand("") {
+            KotlinWithGradleConfigurator.changeLanguageVersion(buildGradle, "1.1", false)
+        }
+        myFixture.checkResult(
+                """apply plugin: 'kotlin'
+                  |compileKotlin {
+                  |    kotlinOptions {
+                  |        languageVersion = "1.1"
+                  |    }
+                  |}
+                  |""".trimMargin("|"))
+    }
 }