From b5ea31d53f6c5995c87403c336eb8aa717c6048c Mon Sep 17 00:00:00 2001
From: Andreas Dangel <andreas.dangel@pmd-code.org>
Date: Thu, 16 Feb 2023 16:40:24 +0100
Subject: [PATCH] [core] Support environment variable CLASSPATH with pmd.bat
 under Windows

---
 docs/pages/pmd/userdocs/cli_reference.md    | 18 ++++++++++++++++--
 docs/pages/release_notes.md                 |  2 ++
 pmd-dist/src/main/resources/scripts/pmd.bat |  7 ++++++-
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/docs/pages/pmd/userdocs/cli_reference.md b/docs/pages/pmd/userdocs/cli_reference.md
index 2201d4ab53..cbb6fba4d5 100644
--- a/docs/pages/pmd/userdocs/cli_reference.md
+++ b/docs/pages/pmd/userdocs/cli_reference.md
@@ -189,8 +189,22 @@ if you want to analyze a project, that uses one of OpenJDK's [Preview Language F
 
 Just set the environment variable `PMD_JAVA_OPTS` before executing PMD, e.g.
 
-    export PMD_JAVA_OPTS="--enable-preview"
-    ./run.sh pmd -d ../../../src/main/java/ -f text -R rulesets/java/quickstart.xml
+```shell
+export PMD_JAVA_OPTS="--enable-preview"
+./run.sh pmd -d ../../../src/main/java/ -f text -R rulesets/java/quickstart.xml
+```
+
+## Additional runtime classpath
+
+If you develop custom rules and package them as a jar file, you need to add it to PMD's runtime classpath.
+You can either copy the jar file into the `lib/` subfolder alongside the other jar files, that are in PMD's
+standard distribution.
+
+Or you can set the environment variable `CLASSPATH` before starting PMD, e.g.
+
+```shell
+CLASSPATH=custom-rule-example.jar ./run.sh pmd -d ../../../src/main/java/ -f text -R myrule.xml
+```
 
 ## Exit Status
 
diff --git a/docs/pages/release_notes.md b/docs/pages/release_notes.md
index 75d5480d5d..c302ba42ea 100644
--- a/docs/pages/release_notes.md
+++ b/docs/pages/release_notes.md
@@ -15,6 +15,8 @@ This is a {{ site.pmd.release_type }} release.
 ### New and noteworthy
 
 ### Fixed Issues
+* core
+  * [#4395](https://github.com/pmd/pmd/issues/4395): \[core] Support environment variable CLASSPATH with pmd.bat under Windows
 * java-errorprone
   * [#4393](https://github.com/pmd/pmd/issues/4393): \[java] MissingStaticMethodInNonInstantiatableClass false-positive for Lombok's @UtilityClass for classes with non-private fields
 
diff --git a/pmd-dist/src/main/resources/scripts/pmd.bat b/pmd-dist/src/main/resources/scripts/pmd.bat
index b3b2c78699..4c2023b8c8 100755
--- a/pmd-dist/src/main/resources/scripts/pmd.bat
+++ b/pmd-dist/src/main/resources/scripts/pmd.bat
@@ -2,5 +2,10 @@
 set TOPDIR="%~dp0.."
 set OPTS=
 set MAIN_CLASS=net.sourceforge.pmd.PMD
+set PMD_CLASSPATH=%TOPDIR%\lib\*
 
-java %PMD_JAVA_OPTS% -classpath %TOPDIR%\lib\* %OPTS% %MAIN_CLASS% %*
+if [%CLASSPATH%] NEQ [] (
+    set PMD_CLASSPATH=%CLASSPATH%;%PMD_CLASSPATH%
+)
+
+java %PMD_JAVA_OPTS% -classpath %PMD_CLASSPATH% %OPTS% %MAIN_CLASS% %*