From 82108b7d24794288571a2f5bd6100b6417a67b5c Mon Sep 17 00:00:00 2001
From: Toshiaki Kameyama <kmymtsak@gmail.com>
Date: Sun, 21 Jun 2020 16:24:42 +0900
Subject: [PATCH] UnusedPrivateClass: don't report imported classes (#2812)

---
 .../detekt/rules/style/UnusedPrivateClass.kt  | 15 +++++++++++-
 .../rules/style/UnusedPrivateClassSpec.kt     | 23 +++++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/detekt-rules/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/UnusedPrivateClass.kt b/detekt-rules/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/UnusedPrivateClass.kt
index 1b81d198f..863d4f44c 100644
--- a/detekt-rules/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/UnusedPrivateClass.kt
+++ b/detekt-rules/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/UnusedPrivateClass.kt
@@ -18,6 +18,7 @@ import org.jetbrains.kotlin.psi.KtDoubleColonExpression
 import org.jetbrains.kotlin.psi.KtExpression
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.psi.KtFunctionType
+import org.jetbrains.kotlin.psi.KtImportDirective
 import org.jetbrains.kotlin.psi.KtNameReferenceExpression
 import org.jetbrains.kotlin.psi.KtNamedDeclaration
 import org.jetbrains.kotlin.psi.KtNamedFunction
@@ -63,9 +64,16 @@ class UnusedPrivateClass(config: Config = Config.empty) : Rule(config) {
 
         private val privateClasses = mutableSetOf<KtNamedDeclaration>()
         private val namedClasses = mutableSetOf<String>()
+        private val importDirectives = mutableSetOf<String>()
 
         fun getUnusedClasses(): List<KtNamedDeclaration> {
-            return privateClasses.filter { it.nameAsSafeName.identifier !in namedClasses }
+            return privateClasses.filter { !it.isUsed() }
+        }
+
+        private fun KtNamedDeclaration.isUsed(): Boolean {
+            if (nameAsSafeName.identifier in namedClasses) return true
+            val fqName = fqName?.asString()
+            return fqName != null && importDirectives.any { it.startsWith(fqName) }
         }
 
         override fun visitClass(klass: KtClass) {
@@ -78,6 +86,11 @@ class UnusedPrivateClass(config: Config = Config.empty) : Rule(config) {
             super.visitClass(klass)
         }
 
+        override fun visitImportDirective(importDirective: KtImportDirective) {
+            importDirectives.addIfNotNull(importDirective.importedFqName?.asString())
+            super.visitImportDirective(importDirective)
+        }
+
         override fun visitAnnotationEntry(annotationEntry: KtAnnotationEntry) {
             namedClasses.addIfNotNull(annotationEntry.typeReference?.text)
             super.visitAnnotationEntry(annotationEntry)
diff --git a/detekt-rules/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/style/UnusedPrivateClassSpec.kt b/detekt-rules/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/style/UnusedPrivateClassSpec.kt
index ccd77fc90..37aaedb75 100644
--- a/detekt-rules/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/style/UnusedPrivateClassSpec.kt
+++ b/detekt-rules/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/style/UnusedPrivateClassSpec.kt
@@ -1,6 +1,7 @@
 package io.gitlab.arturbosch.detekt.rules.style
 
 import io.gitlab.arturbosch.detekt.test.compileAndLint
+import io.gitlab.arturbosch.detekt.test.lint
 import org.assertj.core.api.Assertions.assertThat
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
@@ -361,5 +362,27 @@ class UnusedPrivateClassSpec : Spek({
 
             assertThat(findings).isEmpty()
         }
+
+        it("does not report imported enum class - #2809") {
+            val code = """
+                package com.example
+
+                import com.example.C.E.E1
+
+                class C {
+                    fun test() {
+                        println(E1)
+                    }
+
+                    private enum class E {
+                        E1,
+                        E2,
+                        E3
+                    }
+                }
+            """
+            val findings = UnusedPrivateClass().lint(code)
+            assertThat(findings).isEmpty()
+        }
     }
 })