[java] IDEA-355048 Support binary files (.class) in split mode

GitOrigin-RevId: ea7a098ef33476d53dd8bf061810835510885466

java/java-frontback-psi-impl/src/com/intellij/java/frontback/psi/impl/JavaLangLevelProjectCustomDataSynchronizer.kt

@@ -37,4 +37,7 @@ class JavaLangLevelProjectCustomDataSynchronizer : ProjectCustomDataSynchronizer
 class LanguageLevelHolder(val languageLevel: LanguageLevel)
 
 @Serializable
-class NullableLanguageLevelHolder(val languageLevel: LanguageLevel?)
+class NullableLanguageLevelHolder(val languageLevel: LanguageLevel?)
+
+@Serializable
+class ClassFileInformation(val isClassFile: Boolean?)

java/java-impl/src/META-INF/JavaPlugin.xml

@@ -2811,6 +2811,7 @@
     <postStartupActivity implementation="com.intellij.ide.FileNotInSourceRootChecker"/>
 
     <virtualFileCustomDataProvider implementation="com.intellij.openapi.roots.impl.JavaLangLevelVirtualFileCustomDataProvider"/>
+    <virtualFileCustomDataProvider implementation="com.intellij.openapi.roots.impl.JavaClassVirtualFileCustomDataProvider"/>
 
     <spellchecker.dictionary.checker implementation="com.intellij.java.frameworks.MavenDictionaryChecker"/>
 

java/java-impl/src/com/intellij/openapi/roots/impl/JavaClassVirtualFileCustomDataProvider.kt

@@ -0,0 +1,49 @@
+// Copyright 2000-2023 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.openapi.roots.impl
+
+import com.intellij.ide.highlighter.JavaClassFileType
+import com.intellij.java.frontback.psi.impl.ClassFileInformation
+import com.intellij.openapi.application.readAction
+import com.intellij.openapi.diagnostic.logger
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.roots.FileIndexFacade
+import com.intellij.openapi.vfs.VirtualFile
+import com.intellij.openapi.vfs.VirtualFileCustomDataProvider
+import com.intellij.util.concurrency.annotations.RequiresReadLock
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.FlowCollector
+import kotlinx.coroutines.flow.emptyFlow
+import kotlin.reflect.KType
+import kotlin.reflect.typeOf
+
+class JavaClassVirtualFileCustomDataProvider : VirtualFileCustomDataProvider<ClassFileInformation> {
+  companion object {
+    val LOG = logger<JavaClassVirtualFileCustomDataProvider>()
+  }
+
+  override val id: String = "javaClassVirtualFile"
+
+  override val dataType: KType
+    get() = typeOf<ClassFileInformation>()
+
+  override fun getValues(project: Project, virtualFile: VirtualFile): Flow<ClassFileInformation> {
+    if (virtualFile.fileType != JavaClassFileType.INSTANCE) return emptyFlow()
+    return object : Flow<ClassFileInformation> {
+      override suspend fun collect(collector: FlowCollector<ClassFileInformation>) {
+        collector.emit(readAction {
+          createClassFileInformation(project, virtualFile)
+        })
+      }
+    }
+  }
+
+  @RequiresReadLock
+  private fun createClassFileInformation(
+    project: Project,
+    virtualFile: VirtualFile,
+  ): ClassFileInformation {
+    val fileIndex = FileIndexFacade.getInstance(project)
+    val isOutOfLibrary = !fileIndex.isInLibraryClasses(virtualFile) && fileIndex.isInSource(virtualFile)
+    return ClassFileInformation(!isOutOfLibrary)
+  }
+}