From 4a805f4284d47b6a660e8cfca719f67056fb2d29 Mon Sep 17 00:00:00 2001
From: Andreas Dangel <andreas.dangel@pmd-code.org>
Date: Thu, 17 Mar 2022 11:14:54 +0100
Subject: [PATCH] [java] Fix ClassWithOnlyPrivateConstructorsShouldBeFinal with
 multiple classes

Fixes #3851
---
 docs/pages/release_notes.md                      |  2 ++
 .../src/main/resources/category/java/design.xml  | 16 +++++++++++-----
 ...sWithOnlyPrivateConstructorsShouldBeFinal.xml | 15 +++++++++++++++
 3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/docs/pages/release_notes.md b/docs/pages/release_notes.md
index ae817d64cb..2e198cd082 100644
--- a/docs/pages/release_notes.md
+++ b/docs/pages/release_notes.md
@@ -57,6 +57,8 @@ The CLI itself remains compatible, if you run PMD via command-line, no action is
     *   [#3299](https://github.com/pmd/pmd/issues/3299): \[core] Deprecate system properties of PMDCommandLineInterface
 *   doc
     *   [#3812](https://github.com/pmd/pmd/issues/3812): \[doc] Documentation website table of contents broken on pages with many subheadings
+*   java-design
+    *   [#3851](https://github.com/pmd/pmd/issues/3851): \[java] ClassWithOnlyPrivateConstructorsShouldBeFinal - false negative when a compilation unit contains two class declarations
 
 ### API Changes
 
diff --git a/pmd-java/src/main/resources/category/java/design.xml b/pmd-java/src/main/resources/category/java/design.xml
index 1b30305f92..f071a261f9 100644
--- a/pmd-java/src/main/resources/category/java/design.xml
+++ b/pmd-java/src/main/resources/category/java/design.xml
@@ -338,11 +338,17 @@ is invoked by a inner class.
             <property name="xpath">
                 <value>
 <![CDATA[
-//TypeDeclaration[count(../TypeDeclaration) = 1]/ClassOrInterfaceDeclaration
-[@Final = false()]
-[ClassOrInterfaceBody/ClassOrInterfaceBodyDeclaration/ConstructorDeclaration[@Private = true()]]
-[not(./ClassOrInterfaceBody/ClassOrInterfaceBodyDeclaration/ConstructorDeclaration[(@Public = true()) or (@Protected = true()) or (@PackagePrivate = true())])]
-[not(.//ClassOrInterfaceDeclaration)]
+//TypeDeclaration
+  /ClassOrInterfaceDeclaration
+  [@Final = false()]
+  (: at least one private constructor :)
+  [ClassOrInterfaceBody/ClassOrInterfaceBodyDeclaration/ConstructorDeclaration[@Private = true()]]
+  (: no public constructor :)
+  [not(./ClassOrInterfaceBody/ClassOrInterfaceBodyDeclaration/ConstructorDeclaration[(@Public = true()) or (@Protected = true()) or (@PackagePrivate = true())])]
+  (: not a base class in the same compilation unit :)
+  [not(@SimpleName = ../../TypeDeclaration/ClassOrInterfaceDeclaration/ExtendsList/ClassOrInterfaceType/@Image)]
+  (: not a base class for a inner class in the same compilation unit :)
+  [not(@SimpleName = .//ClassOrInterfaceDeclaration/ExtendsList/ClassOrInterfaceType/@Image)]
 ]]>
                 </value>
             </property>
diff --git a/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/design/xml/ClassWithOnlyPrivateConstructorsShouldBeFinal.xml b/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/design/xml/ClassWithOnlyPrivateConstructorsShouldBeFinal.xml
index f7c9e75d8b..8d6ffe733b 100644
--- a/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/design/xml/ClassWithOnlyPrivateConstructorsShouldBeFinal.xml
+++ b/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/design/xml/ClassWithOnlyPrivateConstructorsShouldBeFinal.xml
@@ -170,6 +170,21 @@ public class Outer {
     private abstract class Base {
         private void run() {}
     }
+}
+        ]]></code>
+    </test-code>
+
+    <test-code>
+        <description>[java] ClassWithOnlyPrivateConstructorsShouldBeFinal - false negative when a compilation unit contains two class declarations #3851</description>
+        <expected-problems>1</expected-problems>
+        <expected-linenumbers>1</expected-linenumbers>
+        <code><![CDATA[
+public class Example { // false-negative here
+    private Example() {
+    }
+}
+
+class Another {
 }
         ]]></code>
     </test-code>