Fix "Illegal Android Identifier" inspection reports non-instrumentation unit tests (KT-22168)

idea/idea-android/src/org/jetbrains/kotlin/android/inspection/IllegalIdentifierInspection.kt

@@ -16,20 +16,36 @@
 
 package org.jetbrains.kotlin.android.inspection
 
+import com.android.builder.model.AndroidProject.ARTIFACT_UNIT_TEST
+import com.android.tools.idea.AndroidPsiUtils
+import com.android.tools.idea.gradle.project.model.AndroidModuleModel
 import com.intellij.codeInspection.LocalInspectionToolSession
 import com.intellij.codeInspection.ProblemHighlightType
 import com.intellij.codeInspection.ProblemsHolder
 import com.intellij.openapi.application.ApplicationManager
+import com.intellij.openapi.module.Module
+import com.intellij.openapi.roots.ProjectRootModificationTracker
+import com.intellij.openapi.util.Key
+import com.intellij.openapi.util.SystemInfo
+import com.intellij.openapi.util.text.StringUtil
+import com.intellij.openapi.vfs.VirtualFile
 import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiElementVisitor
+import com.intellij.psi.util.CachedValuesManager
+import org.jetbrains.android.facet.AndroidFacet
 import org.jetbrains.kotlin.android.getAndroidFacetForFile
 import org.jetbrains.kotlin.idea.inspections.AbstractKotlinInspection
 import org.jetbrains.kotlin.idea.quickfix.RenameIdentifierFix
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.KtPsiUtil
 import org.jetbrains.kotlin.psi.KtVisitorVoid
+import java.io.File
 
 class IllegalIdentifierInspection : AbstractKotlinInspection() {
+    private class JunitPaths(val paths: List<File>, val generationId: Long) {
+        companion object : Key<JunitPaths>("AndroidModuleJunitPaths")
+    }
+
     override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean, session: LocalInspectionToolSession): PsiElementVisitor {
         return object : KtVisitorVoid() {
             override fun visitElement(element: PsiElement) {
@@ -44,13 +60,37 @@ class IllegalIdentifierInspection : AbstractKotlinInspection() {
                 if (unquotedName.isEmpty()) return
 
                 if (!unquotedName.all { isValidDalvikCharacter(it) } && checkAndroidFacet(element)) {
-                    holder.registerProblem(element,
-                                           "Identifier not allowed in Android projects",
-                                           ProblemHighlightType.GENERIC_ERROR,
-                                           RenameIdentifierFix())
+                    if (element.isInUnitTests()) {
+                        return
+                    }
+
+                    holder.registerProblem(
+                        element,
+                        "Identifier not allowed in Android projects",
+                        ProblemHighlightType.GENERIC_ERROR,
+                        RenameIdentifierFix()
+                    )
                 }
             }
 
+            private fun PsiElement.isInUnitTests(): Boolean {
+                val containingFile = containingFile?.virtualFile?.let { getIoFile(it) }
+                val module = AndroidPsiUtils.getModuleSafely(this)
+
+                if (module != null && containingFile != null) {
+                    val currentGenerationId = ProjectRootModificationTracker.getInstance(module.project).modificationCount
+                    val junitTestPaths = module.getUserData(JunitPaths)
+                        ?.takeIf { it.generationId == currentGenerationId }
+                            ?: JunitPaths(getJunitTestPaths(module), currentGenerationId).also { module.putUserData(JunitPaths, it) }
+
+                    if (junitTestPaths.paths.any { containingFile.startsWith(it) }) {
+                        return true
+                    }
+                }
+
+                return false
+            }
+
             private fun checkAndroidFacet(element: PsiElement): Boolean {
                 return element.getAndroidFacetForFile() != null || ApplicationManager.getApplication().isUnitTestMode
             }
@@ -70,4 +110,21 @@ class IllegalIdentifierInspection : AbstractKotlinInspection() {
         }
     }
 
+    private fun getJunitTestPaths(module: Module): List<File> {
+        val androidFacet = AndroidFacet.getInstance(module) ?: return emptyList()
+        val androidModuleModel = AndroidModuleModel.get(androidFacet) ?: return emptyList()
+
+        return androidModuleModel.getTestSourceProviders(ARTIFACT_UNIT_TEST).flatMap { it.javaDirectories }
+    }
+
+    private fun getIoFile(virtualFile: VirtualFile): File? {
+        var path = virtualFile.path
+
+        // Taken from LocalFileSystemBase.convertToIOFile
+        if (StringUtil.endsWithChar(path, ':') && path.length == 2 && SystemInfo.isWindows) {
+            path += "/"
+        }
+
+        return File(path).takeIf { it.exists() }
+    }
 }