diff --git a/compiler/frontend/src/org/jetbrains/kotlin/analyzer/AnalyzerFacade.kt b/compiler/frontend/src/org/jetbrains/kotlin/analyzer/AnalyzerFacade.kt
index a287b01a820..8f81bb1707c 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/analyzer/AnalyzerFacade.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/analyzer/AnalyzerFacade.kt
@@ -18,7 +18,9 @@ package org.jetbrains.kotlin.analyzer
 
 import com.intellij.openapi.components.ServiceManager
 import com.intellij.openapi.project.Project
+import com.intellij.openapi.util.ModificationTracker
 import com.intellij.psi.search.GlobalSearchScope
+import com.intellij.psi.util.PsiModificationTracker
 import org.jetbrains.kotlin.builtins.DefaultBuiltIns
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.config.LanguageVersionSettings
@@ -85,9 +87,17 @@ class ResolverForProjectImpl<M : ModuleInfo>(
         private val packagePartProviderFactory: (M, ModuleContent) -> PackagePartProvider = { _, _ -> PackagePartProvider.Empty },
         private val firstDependency: M? = null,
         private val modulePlatforms: (M) -> MultiTargetPlatform?,
-        private val packageOracleFactory: PackageOracleFactory = PackageOracleFactory.OptimisticFactory
+        private val packageOracleFactory: PackageOracleFactory = PackageOracleFactory.OptimisticFactory,
+        private val invalidateOnOOCB: Boolean = true
 ) : ResolverForProject<M>() {
-    private val descriptorByModule = mutableMapOf<M, ModuleDescriptorImpl>()
+
+    private class ModuleData(
+            val moduleDescriptor: ModuleDescriptorImpl,
+            val modificationTracker: ModificationTracker?,
+            val modificationCount: Long?
+    )
+
+    private val descriptorByModule = mutableMapOf<M, ModuleData>()
     private val moduleInfoByDescriptor = mutableMapOf<ModuleDescriptorImpl, M>()
     val modules = modules.toSet()
 
@@ -156,18 +166,42 @@ class ResolverForProjectImpl<M : ModuleInfo>(
     private fun doGetDescriptorForModule(module: M): ModuleDescriptorImpl {
         if (module in modules) {
             return projectContext.storageManager.compute {
-                descriptorByModule.getOrPut(module) {
-                    ModuleDescriptorImpl(module.name,
-                                         projectContext.storageManager, builtIns, modulePlatforms(module), module.capabilities).apply {
-                        moduleInfoByDescriptor[this] = module
-                        setupModuleDescriptor(module, this)
-                    }
+                var moduleData = descriptorByModule.getOrPut(module) {
+                    createModuleDescriptor(module)
                 }
+                val currentModCount = moduleData.modificationTracker?.modificationCount
+                if (currentModCount != null && currentModCount > moduleData.modificationCount!!) {
+                    moduleData = recreateModuleDescriptor(module)
+                }
+                moduleData.moduleDescriptor
             }
         }
 
         return delegateResolver.descriptorForModule(module) as ModuleDescriptorImpl
     }
+
+    private fun recreateModuleDescriptor(module: M): ModuleData {
+        val oldDescriptor = descriptorByModule[module]?.moduleDescriptor
+        if (oldDescriptor != null) {
+            oldDescriptor.isValid = false
+            moduleInfoByDescriptor.remove(oldDescriptor)
+            resolverByModuleDescriptor.remove(oldDescriptor)
+        }
+
+        val moduleData = createModuleDescriptor(module)
+        descriptorByModule[module] = moduleData
+        return moduleData
+    }
+
+    private fun createModuleDescriptor(module: M): ModuleData {
+        val moduleDescriptor = ModuleDescriptorImpl(module.name,
+                                                    projectContext.storageManager, builtIns, modulePlatforms(module), module.capabilities)
+        moduleInfoByDescriptor[moduleDescriptor] = module
+        setupModuleDescriptor(module, moduleDescriptor)
+        val modificationTracker = (module as? TrackableModuleInfo)?.createModificationTracker() ?:
+                                  (PsiModificationTracker.SERVICE.getInstance(projectContext.project).outOfCodeBlockModificationTracker.takeIf { invalidateOnOOCB })
+        return ModuleData(moduleDescriptor, modificationTracker, modificationTracker?.modificationCount)
+    }
 }
 
 data class ModuleContent(
@@ -207,6 +241,10 @@ interface ModuleInfo {
     }
 }
 
+interface TrackableModuleInfo : ModuleInfo {
+    fun createModificationTracker(): ModificationTracker
+}
+
 abstract class AnalyzerFacade {
     abstract fun <M : ModuleInfo> createResolverForModule(
             moduleInfo: M,
diff --git a/core/descriptors/src/org/jetbrains/kotlin/descriptors/ModuleDescriptor.kt b/core/descriptors/src/org/jetbrains/kotlin/descriptors/ModuleDescriptor.kt
index 88e301b4863..b69ae2b1173 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/descriptors/ModuleDescriptor.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/descriptors/ModuleDescriptor.kt
@@ -48,4 +48,6 @@ interface ModuleDescriptor : DeclarationDescriptor {
     class Capability<T>(val name: String) {
         override fun toString() = name
     }
+
+    val isValid: Boolean
 }
diff --git a/core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/ModuleDescriptorImpl.kt b/core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/ModuleDescriptorImpl.kt
index f61eaaa28f6..96dbf20cb66 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/ModuleDescriptorImpl.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/ModuleDescriptorImpl.kt
@@ -47,6 +47,14 @@ class ModuleDescriptorImpl @JvmOverloads constructor(
     private var dependencies: ModuleDependencies? = null
     private var packageFragmentProviderForModuleContent: PackageFragmentProvider? = null
 
+    override var isValid: Boolean = true
+
+    private fun assertValid() {
+        if (!isValid) {
+            throw IllegalStateException("Accessing invalid module descriptor $this")
+        }
+    }
+
     private val packages = storageManager.createMemoizedFunction<FqName, PackageViewDescriptor> {
         fqName: FqName -> LazyPackageViewDescriptorImpl(this, fqName, storageManager)
     }
@@ -60,9 +68,13 @@ class ModuleDescriptorImpl @JvmOverloads constructor(
     override val allImplementingModules: Set<ModuleDescriptor>
         get() = this.dependencies.sure { "Dependencies of module $id were not set" }.allImplementingModules
 
-    override fun getPackage(fqName: FqName): PackageViewDescriptor = packages(fqName)
+    override fun getPackage(fqName: FqName): PackageViewDescriptor {
+        assertValid()
+        return packages(fqName)
+    }
 
     override fun getSubPackagesOf(fqName: FqName, nameFilter: (Name) -> Boolean): Collection<FqName> {
+        assertValid()
         return packageFragmentProvider.getSubPackagesOf(fqName, nameFilter)
     }
 
@@ -117,7 +129,10 @@ class ModuleDescriptorImpl @JvmOverloads constructor(
     }
 
     val packageFragmentProvider: PackageFragmentProvider
-        get() = packageFragmentProviderForWholeModuleWithDependencies
+        get() {
+            assertValid()
+            return packageFragmentProviderForWholeModuleWithDependencies
+        }
 
     @Suppress("UNCHECKED_CAST")
     override fun <T> getCapability(capability: ModuleDescriptor.Capability<T>) = capabilities[capability] as? T
diff --git a/core/descriptors/src/org/jetbrains/kotlin/types/ErrorUtils.java b/core/descriptors/src/org/jetbrains/kotlin/types/ErrorUtils.java
index 5a9a92b5ddc..381751cf9e9 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/types/ErrorUtils.java
+++ b/core/descriptors/src/org/jetbrains/kotlin/types/ErrorUtils.java
@@ -122,6 +122,11 @@ public class ErrorUtils {
             public KotlinBuiltIns getBuiltIns() {
                 return DefaultBuiltIns.getInstance();
             }
+
+            @Override
+            public boolean isValid() {
+                return false;
+            }
         };
     }
 
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/IdeaModuleInfos.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/IdeaModuleInfos.kt
index cf2834c89be..2b2f34e4313 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/IdeaModuleInfos.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/IdeaModuleInfos.kt
@@ -23,6 +23,7 @@ import com.intellij.openapi.projectRoots.Sdk
 import com.intellij.openapi.roots.*
 import com.intellij.openapi.roots.impl.libraries.LibraryEx
 import com.intellij.openapi.roots.libraries.Library
+import com.intellij.openapi.util.ModificationTracker
 import com.intellij.openapi.vfs.VirtualFile
 import com.intellij.psi.search.GlobalSearchScope
 import com.intellij.psi.util.CachedValueProvider
@@ -30,9 +31,11 @@ import com.intellij.psi.util.CachedValuesManager
 import com.intellij.util.PathUtil
 import com.intellij.util.SmartList
 import org.jetbrains.kotlin.analyzer.ModuleInfo
+import org.jetbrains.kotlin.analyzer.TrackableModuleInfo
 import org.jetbrains.kotlin.caches.resolve.LibraryModuleInfo
 import org.jetbrains.kotlin.descriptors.ModuleDescriptor
 import org.jetbrains.kotlin.idea.framework.getLibraryPlatform
+import org.jetbrains.kotlin.idea.project.KotlinModuleModificationTracker
 import org.jetbrains.kotlin.idea.project.TargetPlatformDetector
 import org.jetbrains.kotlin.idea.stubindex.KotlinSourceFilterScope
 import org.jetbrains.kotlin.idea.util.isInSourceContentWithoutInjected
@@ -97,7 +100,7 @@ private fun ideaModelDependencies(module: Module, productionOnly: Boolean): List
     return result.toList()
 }
 
-interface ModuleSourceInfo : IdeaModuleInfo {
+interface ModuleSourceInfo : IdeaModuleInfo, TrackableModuleInfo {
     val module: Module
 
     override val displayedName get() = module.name
@@ -107,6 +110,9 @@ interface ModuleSourceInfo : IdeaModuleInfo {
 
     override val platform: TargetPlatform
         get() = TargetPlatformDetector.getPlatform(module)
+
+    override fun createModificationTracker(): ModificationTracker =
+            KotlinModuleModificationTracker(module)
 }
 
 data class ModuleProductionSourceInfo(override val module: Module) : ModuleSourceInfo {
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/KotlinCacheServiceImpl.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/KotlinCacheServiceImpl.kt
index 4abf109c3f3..4f6bc881abb 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/KotlinCacheServiceImpl.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/KotlinCacheServiceImpl.kt
@@ -125,6 +125,7 @@ class KotlinCacheServiceImpl(val project: Project) : KotlinCacheService {
                        LibraryModificationTracker.getInstance(project),
                        ProjectRootModificationTracker.getInstance(project)
                 ),
+                invalidateOnOOCB = false,
                 reuseDataFrom = null
         )
 
@@ -134,6 +135,7 @@ class KotlinCacheServiceImpl(val project: Project) : KotlinCacheService {
                 project, librariesContext, settings,
                 reuseDataFrom = facadeForSdk,
                 moduleFilter = { it is LibraryInfo },
+                invalidateOnOOCB = false,
                 dependencies = listOf(
                         LibraryModificationTracker.getInstance(project),
                         ProjectRootModificationTracker.getInstance(project)
@@ -146,7 +148,10 @@ class KotlinCacheServiceImpl(val project: Project) : KotlinCacheService {
                 project, modulesContext, settings,
                 reuseDataFrom = facadeForLibraries,
                 moduleFilter = { !it.isLibraryClasses() },
-                dependencies = listOf(PsiModificationTracker.OUT_OF_CODE_BLOCK_MODIFICATION_COUNT)
+                dependencies = listOf(
+                        LibraryModificationTracker.getInstance(project),
+                        ProjectRootModificationTracker.getInstance(project)
+                )
         )
     }
 
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ModuleDependencyMapper.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ModuleDependencyMapper.kt
index 96142c2965c..8c4c62e946e 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ModuleDependencyMapper.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ModuleDependencyMapper.kt
@@ -52,7 +52,8 @@ fun createModuleResolverProvider(
         moduleFilter: (IdeaModuleInfo) -> Boolean,
         allModules: Collection<IdeaModuleInfo>?,
         providedBuiltIns: KotlinBuiltIns?, // null means create new builtins based on SDK
-        dependencies: Collection<Any>
+        dependencies: Collection<Any>,
+        invalidateOnOOCB: Boolean = true
 ): ModuleResolverProvider {
     val builtIns = providedBuiltIns ?: createBuiltIns(analysisSettings, globalContext)
 
@@ -82,7 +83,8 @@ fun createModuleResolverProvider(
             delegateResolver, { _, c -> IDEPackagePartProvider(c.moduleContentScope) },
             analysisSettings.sdk?.let { SdkInfo(project, it) },
             modulePlatforms = { module -> module.platform?.multiTargetPlatform },
-            packageOracleFactory = project.service<IdePackageOracleFactory>()
+            packageOracleFactory = project.service<IdePackageOracleFactory>(),
+            invalidateOnOOCB = invalidateOnOOCB
     )
 
     if (providedBuiltIns == null && builtIns is JvmBuiltIns) {
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ProjectResolutionFacade.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ProjectResolutionFacade.kt
index 90f9ab00a76..194ef99b6e3 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ProjectResolutionFacade.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ProjectResolutionFacade.kt
@@ -30,14 +30,15 @@ import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.resolve.CompositeBindingContext
 
 internal class ProjectResolutionFacade(
-        val debugString: String,
-        val resolverDebugName: String,
+        private val debugString: String,
+        private val resolverDebugName: String,
         val project: Project,
         val globalContext: GlobalContextImpl,
         val settings: PlatformAnalysisSettings,
         val reuseDataFrom: ProjectResolutionFacade?,
         val moduleFilter: (IdeaModuleInfo) -> Boolean,
         val dependencies: List<Any>,
+        private val invalidateOnOOCB: Boolean = true,
         val syntheticFiles: Collection<KtFile> = listOf(),
         val allModules: Collection<IdeaModuleInfo>? = null // null means create resolvers for modules from idea model
 ) {
@@ -61,11 +62,12 @@ internal class ProjectResolutionFacade(
                 delegateResolver = delegateResolverForProject, moduleFilter = moduleFilter,
                 allModules = allModules,
                 providedBuiltIns = delegateResolverProvider?.builtIns,
-                dependencies = dependencies
+                dependencies = dependencies,
+                invalidateOnOOCB = invalidateOnOOCB
         )
     }
 
-    val moduleResolverProvider: ModuleResolverProvider
+    private val moduleResolverProvider: ModuleResolverProvider
         get() = globalContext.storageManager.compute { cachedValue.value }
 
     fun resolverForModuleInfo(moduleInfo: IdeaModuleInfo) = moduleResolverProvider.resolverForProject.resolverForModule(moduleInfo)
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/project/KotlinCodeBlockModificationListener.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/project/KotlinCodeBlockModificationListener.kt
index 475b62539c8..153f4ebdbaf 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/project/KotlinCodeBlockModificationListener.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/project/KotlinCodeBlockModificationListener.kt
@@ -16,8 +16,12 @@
 
 package org.jetbrains.kotlin.idea.project
 
+import com.intellij.openapi.module.Module
+import com.intellij.openapi.module.ModuleUtil
 import com.intellij.openapi.project.Project
+import com.intellij.openapi.roots.ModuleRootManager
 import com.intellij.openapi.util.Key
+import com.intellij.openapi.util.ModificationTracker
 import com.intellij.pom.PomManager
 import com.intellij.pom.PomModelAspect
 import com.intellij.pom.event.PomModelEvent
@@ -28,6 +32,7 @@ import com.intellij.psi.PsiCodeFragment
 import com.intellij.psi.PsiElement
 import com.intellij.psi.impl.PsiModificationTrackerImpl
 import com.intellij.psi.util.PsiModificationTracker
+import com.intellij.util.CommonProcessors
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.getTopmostParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.isAncestor
@@ -41,10 +46,27 @@ class KotlinCodeBlockModificationListener(
         project: Project,
         private val treeAspect: TreeAspect
 ) {
+    private val perModuleModCount = mutableMapOf<Module, Long>()
+    private val modificationTrackerImpl = modificationTracker as PsiModificationTrackerImpl
+
+    private var lastAffectedModule: Module? = null
+    private var lastAffectedModuleModCount = -1L
+
+    // All modifications since that count are known to be single-module modifications reflected in
+    // perModuleModCount map
+    private var perModuleChangesHighwatermark: Long? = null
+
+    fun getModificationCount(module: Module): Long {
+        return perModuleModCount[module] ?:
+               perModuleChangesHighwatermark ?:
+               modificationTrackerImpl.outOfCodeBlockModificationCount
+    }
+
+    fun hasPerModuleModificationCounts() = perModuleChangesHighwatermark != null
+
     init {
         val model = PomManager.getModel(project)
-        @Suppress("NAME_SHADOWING")
-        val modificationTracker = modificationTracker as PsiModificationTrackerImpl
+        val messageBusConnection = project.messageBus.connect()
         model.addModelListener(object: PomModelListener {
             override fun isAspectChangeInteresting(aspect: PomModelAspect): Boolean {
                 return aspect == treeAspect
@@ -58,13 +80,31 @@ class KotlinCodeBlockModificationListener(
                 // contents to be replaced, which is represented in a POM event as an empty list of changed elements
                 if (changedElements.any { getInsideCodeBlockModificationScope(it.psi) == null } ||
                     (file is PsiCodeFragment && changedElements.isEmpty())) {
+                    messageBusConnection.deliverImmediately()
                     if (file.isPhysical) {
-                        modificationTracker.incCounter()
+                        lastAffectedModule = ModuleUtil.findModuleForPsiElement(file)
+                        lastAffectedModuleModCount = modificationTrackerImpl.outOfCodeBlockModificationCount
+                        modificationTrackerImpl.incCounter()
                     }
                     incOutOfBlockModificationCount(file)
                 }
             }
         })
+
+        messageBusConnection.subscribe(PsiModificationTracker.TOPIC, PsiModificationTracker.Listener {
+            val newModCount = modificationTrackerImpl.outOfCodeBlockModificationCount
+            val affectedModule = lastAffectedModule
+            if (affectedModule != null && newModCount == lastAffectedModuleModCount + 1) {
+                if (perModuleChangesHighwatermark== null) {
+                    perModuleChangesHighwatermark = lastAffectedModuleModCount
+                }
+                perModuleModCount[affectedModule] = newModCount
+            }
+            else {
+                perModuleChangesHighwatermark = null
+                perModuleModCount.clear()
+            }
+        })
     }
 
     companion object {
@@ -117,6 +157,8 @@ class KotlinCodeBlockModificationListener(
                 KtProperty::class.java,
                 KtNamedFunction::class.java
         )
+
+        fun getInstance(project: Project) = project.getComponent(KotlinCodeBlockModificationListener::class.java)
     }
 }
 
@@ -124,3 +166,31 @@ private val FILE_OUT_OF_BLOCK_MODIFICATION_COUNT = Key<Long>("FILE_OUT_OF_BLOCK_
 
 val KtFile.outOfBlockModificationCount: Long
     get() = getUserData(FILE_OUT_OF_BLOCK_MODIFICATION_COUNT) ?: 0
+
+class KotlinModuleModificationTracker(val module: Module): ModificationTracker {
+    private val kotlinModCountListener = KotlinCodeBlockModificationListener.getInstance(module.project)
+    private val psiModificationTracker = PsiModificationTracker.SERVICE.getInstance(module.project)
+    private val dependencies by lazy {
+        HashSet<Module>().apply {
+            ModuleRootManager.getInstance(module).orderEntries().recursively().forEachModule(
+                    CommonProcessors.CollectProcessor(this))
+        }
+    }
+
+    override fun getModificationCount(): Long {
+        val currentGlobalCount = psiModificationTracker.outOfCodeBlockModificationCount
+
+        if (kotlinModCountListener.hasPerModuleModificationCounts()) {
+            val selfCount = kotlinModCountListener.getModificationCount(module)
+            if (selfCount == currentGlobalCount) return selfCount
+            var maxCount = selfCount
+            for (dependency in dependencies) {
+                val depCount = kotlinModCountListener.getModificationCount(dependency)
+                if (depCount == currentGlobalCount) return currentGlobalCount
+                if (depCount > maxCount) maxCount = depCount
+            }
+            return maxCount
+        }
+        return currentGlobalCount
+    }
+}
diff --git a/idea/testData/multiModuleHighlighting/recomputeResolversOnChange/m1/m1.kt b/idea/testData/multiModuleHighlighting/recomputeResolversOnChange/m1/m1.kt
new file mode 100644
index 00000000000..22412f84c9e
--- /dev/null
+++ b/idea/testData/multiModuleHighlighting/recomputeResolversOnChange/m1/m1.kt
@@ -0,0 +1,4 @@
+package foo.bar.used
+
+public fun m1() {
+}
\ No newline at end of file
diff --git a/idea/testData/multiModuleHighlighting/recomputeResolversOnChange/m2/m2.kt b/idea/testData/multiModuleHighlighting/recomputeResolversOnChange/m2/m2.kt
new file mode 100644
index 00000000000..65a5fe6f69c
--- /dev/null
+++ b/idea/testData/multiModuleHighlighting/recomputeResolversOnChange/m2/m2.kt
@@ -0,0 +1,5 @@
+import foo.bar.used.*
+
+public fun m2() {
+    m1()
+}
\ No newline at end of file
diff --git a/idea/testData/multiModuleHighlighting/recomputeResolversOnChange/m3/m3.kt b/idea/testData/multiModuleHighlighting/recomputeResolversOnChange/m3/m3.kt
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/idea/tests/org/jetbrains/kotlin/idea/caches/resolve/MultiModuleHighlightingTest.kt b/idea/tests/org/jetbrains/kotlin/idea/caches/resolve/MultiModuleHighlightingTest.kt
index e86b61dc5ec..42e15ea8c57 100644
--- a/idea/tests/org/jetbrains/kotlin/idea/caches/resolve/MultiModuleHighlightingTest.kt
+++ b/idea/tests/org/jetbrains/kotlin/idea/caches/resolve/MultiModuleHighlightingTest.kt
@@ -17,8 +17,16 @@
 package org.jetbrains.kotlin.idea.caches.resolve
 
 import com.intellij.facet.FacetManager
+import com.intellij.openapi.fileEditor.FileDocumentManager
 import com.intellij.openapi.module.Module
+import com.intellij.openapi.projectRoots.Sdk
 import com.intellij.openapi.roots.DependencyScope
+import com.intellij.openapi.roots.ModuleRootManager
+import com.intellij.openapi.roots.ModuleRootModificationUtil
+import com.intellij.psi.PsiDocumentManager
+import com.intellij.psi.PsiManager
+import com.intellij.psi.impl.PsiModificationTrackerImpl
+import com.intellij.psi.util.PsiModificationTracker
 import org.jetbrains.kotlin.analyzer.ModuleInfo
 import org.jetbrains.kotlin.analyzer.ResolverForModuleComputationTracker
 import org.jetbrains.kotlin.cli.common.arguments.K2JVMCompilerArguments
@@ -30,8 +38,12 @@ import org.jetbrains.kotlin.idea.completion.test.withServiceRegistered
 import org.jetbrains.kotlin.idea.facet.KotlinFacetConfiguration
 import org.jetbrains.kotlin.idea.facet.KotlinFacetType
 import org.jetbrains.kotlin.idea.framework.JSLibraryKind
+import org.jetbrains.kotlin.idea.project.KotlinCodeBlockModificationListener
+import org.jetbrains.kotlin.idea.project.KotlinModuleModificationTracker
 import org.jetbrains.kotlin.idea.test.PluginTestCaseBase
+import org.jetbrains.kotlin.idea.util.application.executeWriteCommand
 import org.jetbrains.kotlin.idea.util.application.runWriteAction
+import org.jetbrains.kotlin.idea.util.projectStructure.sdk
 import org.jetbrains.kotlin.test.TestJdkKind.FULL_JDK
 
 open class MultiModuleHighlightingTest : AbstractMultiModuleHighlightingTest() {
@@ -66,20 +78,9 @@ open class MultiModuleHighlightingTest : AbstractMultiModuleHighlightingTest() {
     }
 
     fun testLazyResolvers() {
-        val resolversComputed = mutableSetOf<Module>()
+        val tracker = ResolverTracker()
 
-        val resolversTracker = object : ResolverForModuleComputationTracker {
-            override fun onResolverComputed(moduleInfo: ModuleInfo) {
-                (moduleInfo as IdeaModuleInfo).let {
-                    if (it is ModuleSourceInfo) {
-                        val module = it.module
-                        resolversComputed.add(module)
-                    }
-                }
-            }
-        }
-
-        project.withServiceRegistered<ResolverForModuleComputationTracker, Unit>(resolversTracker) {
+        project.withServiceRegistered<ResolverForModuleComputationTracker, Unit>(tracker) {
             val module1 = module("m1")
             val module2 = module("m2")
             val module3 = module("m3")
@@ -87,15 +88,82 @@ open class MultiModuleHighlightingTest : AbstractMultiModuleHighlightingTest() {
             module3.addDependency(module2)
             module3.addDependency(module1)
 
-            assertTrue(module1 !in resolversComputed)
-            assertTrue(module2 !in resolversComputed)
-            assertTrue(module3 !in resolversComputed)
+            assertTrue(module1 !in tracker.moduleResolversComputed)
+            assertTrue(module2 !in tracker.moduleResolversComputed)
+            assertTrue(module3 !in tracker.moduleResolversComputed)
 
             checkHighlightingInAllFiles { "m3" in file.name }
 
-            assertTrue(module1 in resolversComputed)
-            assertTrue(module2 !in resolversComputed)
-            assertTrue(module3 in resolversComputed)
+            assertTrue(module1 in tracker.moduleResolversComputed)
+            assertTrue(module2 !in tracker.moduleResolversComputed)
+            assertTrue(module3 in tracker.moduleResolversComputed)
+        }
+    }
+
+    class ResolverTracker : ResolverForModuleComputationTracker {
+        val moduleResolversComputed = mutableListOf<Module>()
+        val sdkResolversComputed = mutableListOf<Sdk>()
+
+        override fun onResolverComputed(moduleInfo: ModuleInfo) {
+            when (moduleInfo) {
+                is ModuleSourceInfo -> moduleResolversComputed.add(moduleInfo.module)
+                is SdkInfo -> sdkResolversComputed.add(moduleInfo.sdk)
+            }
+        }
+    }
+
+    fun testRecomputeResolversOnChange() {
+        val tracker = ResolverTracker()
+
+        project.withServiceRegistered<ResolverForModuleComputationTracker, Unit>(tracker) {
+            val module1 = module("m1")
+            val module2 = module("m2")
+            val module3 = module("m3")
+
+            module2.addDependency(module1)
+            module3.addDependency(module2)
+            // Ensure modules have the same SDK instance, and not two distinct SDKs with the same path
+            ModuleRootModificationUtil.setModuleSdk(module2, module1.sdk)
+
+            assertEquals(0, tracker.sdkResolversComputed.size)
+
+            checkHighlightingInAllFiles { "m2" in file.name }
+
+            assertEquals(2, tracker.moduleResolversComputed.size)
+
+            tracker.sdkResolversComputed.clear()
+            tracker.moduleResolversComputed.clear()
+
+            val module1ModCount = KotlinCodeBlockModificationListener.getInstance(myProject).getModificationCount(module1)
+
+            val module1ModTracker = KotlinModuleModificationTracker(module1)
+            val module2ModTracker = KotlinModuleModificationTracker(module2)
+            val module3ModTracker = KotlinModuleModificationTracker(module3)
+
+            val contentRoot = ModuleRootManager.getInstance(module2).contentRoots.single()
+            val m2 = contentRoot.findChild("m2.kt")!!
+            val m2doc = FileDocumentManager.getInstance().getDocument(m2)!!
+            project.executeWriteCommand("a") {
+                m2doc.insertString(m2doc.textLength , "fun foo() = 1")
+                PsiDocumentManager.getInstance(myProject).commitAllDocuments()
+            }
+            val currentModCount = PsiManager.getInstance(project).modificationTracker.outOfCodeBlockModificationCount
+
+            assertEquals(module1ModCount, KotlinCodeBlockModificationListener.getInstance(myProject).getModificationCount(module1))
+            assertEquals(module1ModCount, module1ModTracker.modificationCount)
+            assertEquals(currentModCount, module2ModTracker.modificationCount)
+            assertEquals(currentModCount, module3ModTracker.modificationCount)
+
+            checkHighlightingInAllFiles { "m2" in file.name }
+
+            assertEquals(0, tracker.sdkResolversComputed.size)
+            assertEquals(1, tracker.moduleResolversComputed.size)
+
+            tracker.moduleResolversComputed.clear()
+            (PsiModificationTracker.SERVICE.getInstance(myProject) as PsiModificationTrackerImpl).incOutOfCodeBlockModificationCounter()
+            checkHighlightingInAllFiles { "m2" in file.name }
+            assertEquals(0, tracker.sdkResolversComputed.size)
+            assertEquals(2, tracker.moduleResolversComputed.size)
         }
     }