Caching KtLightClassForSourceDeclaration (KT-21701)

to make their UserData survive for longer, because otherwise a new LightClass with empty UserData comes to Spring every time, but Spring stores a lot of important things in UserData

compiler/light-classes/src/org/jetbrains/kotlin/asJava/classes/KtLightClassForSourceDeclaration.kt

@@ -31,7 +31,9 @@ import com.intellij.psi.search.SearchScope
 import com.intellij.psi.stubs.IStubElementType
 import com.intellij.psi.stubs.StubElement
 import com.intellij.psi.util.CachedValue
+import com.intellij.psi.util.CachedValueProvider
 import com.intellij.psi.util.CachedValuesManager
+import com.intellij.psi.util.PsiModificationTracker.OUT_OF_CODE_BLOCK_MODIFICATION_COUNT
 import com.intellij.util.IncorrectOperationException
 import com.intellij.util.containers.ContainerUtil
 import org.jetbrains.annotations.NonNls
@@ -331,7 +333,13 @@ abstract class KtLightClassForSourceDeclaration(protected val classOrObject: KtC
                 FINAL_KEYWORD to PsiModifier.FINAL)
 
 
-        fun create(classOrObject: KtClassOrObject): KtLightClassForSourceDeclaration? {
+        fun create(classOrObject: KtClassOrObject): KtLightClassForSourceDeclaration? =
+                CachedValuesManager.getCachedValue(classOrObject) {
+                    CachedValueProvider.Result
+                            .create(createNoCache(classOrObject), OUT_OF_CODE_BLOCK_MODIFICATION_COUNT)
+                }
+
+        private fun createNoCache(classOrObject: KtClassOrObject): KtLightClassForSourceDeclaration? {
             if (classOrObject.hasExpectModifier()) {
                 return null
             }

compiler/tests/org/jetbrains/kotlin/asJava/KotlinLightClassTest.kt

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.asJava
+
+import com.intellij.openapi.util.Key
+import com.intellij.psi.search.GlobalSearchScope
+import junit.framework.TestCase
+import org.jetbrains.kotlin.asJava.classes.KtLightClass
+import java.io.File
+
+class KotlinLightClassTest : KotlinAsJavaTestBase() {
+    override fun getKotlinSourceRoots(): List<File> = listOf(
+            File("compiler/testData/asJava/lightClassStructure/ClassObject.kt"),
+            File("compiler/testData/asJava/lightClasses/ideRegression/ImplementingMap.kt")
+    )
+
+    private val key = Key.create<String>("testKey")
+
+    fun testClassInterchangeability() {
+        val lightClass = finder.findClass("test.WithClassObject", GlobalSearchScope.allScope(project)) as KtLightClass
+        val kotlinOrigin = lightClass.kotlinOrigin ?: throw AssertionError("no kotlinOrigin")
+        val testValue = "some data"
+        lightClass.putUserData(key, testValue)
+        val anotherLightClass = kotlinOrigin.toLightClass() ?: throw AssertionError("cant get light class second time")
+        TestCase.assertEquals(testValue, anotherLightClass.getUserData(key))
+        TestCase.assertEquals(lightClass, anotherLightClass)
+    }
+
+    fun testMethodInterchangeability() {
+        val lightClass = finder.findClass("p1.TypeHierarchyMap", GlobalSearchScope.allScope(project)) as KtLightClass
+        val kotlinOrigin = lightClass.kotlinOrigin ?: throw AssertionError("no kotlinOrigin")
+
+        val anotherLightClass = kotlinOrigin.toLightClass() ?: throw AssertionError("cant get light class second time")
+
+        val lightMethod1 = lightClass.methods.first { it.name == "containsKey" }
+
+        val testValue = "some data"
+        lightMethod1.putUserData(key, testValue)
+        val lightMethod2 = anotherLightClass.methods.first { it.name == "containsKey" }
+        TestCase.assertEquals(testValue, lightMethod2.getUserData(key))
+        TestCase.assertEquals(lightMethod1, lightMethod2)
+    }
+
+}