Kotlin rules in java avoid multiple concat statements

.github/copilot-instructions.md

@@ -0,0 +1,48 @@
+# Copilot Instructions for PMD-jPinpoint-rules
+
+## Build, Test, and Lint Commands
+
+- **Build and test all rules:**
+  - `./mvnw clean test`
+  - `./test` (shortcut for `./mvnw test`)
+- **Run a single test class:**
+  - `./mvnw test -Dtest=YourRuleTest`
+- **Merge rule categories into combined rulesets:**
+  - `./merge` (Java)
+  - `./merge kotlin` (Kotlin)
+
+## High-Level Architecture
+
+- **Rule definitions:**
+  - Rules are defined as XPath expressions in XML files under `src/main/resources/category/{java,kotlin}/`.
+  - Each category is registered in `categories.properties`.
+  - Combined rulesets (`rulesets/java/jpinpoint-rules.xml`, `rulesets/kotlin/jpinpoint-kotlin-rules.xml`) are generated by the merger tool.
+- **Tests:**
+  - Each rule has an empty test class (extends `PmdRuleTst`) and a test data XML file with `<test-code>` blocks.
+  - Test classes: `src/test/java/com/jpinpoint/perf/lang/{java,kotlin}/ruleset/{category}/{RuleName}Test.java`
+  - Test data: `src/test/resources/com/jpinpoint/perf/lang/{java,kotlin}/ruleset/{category}/xml/{RuleName}.xml`
+- **Merger tool:**
+  - Located in `rulesets-merger/src/main/java/com/jpinpoint/perf/tools/RulesetMerger.java`.
+  - Merges category XMLs into combined rulesets. Build with `cd rulesets-merger && mvn clean install`.
+
+## Key Conventions
+
+- **Rule XML files:**
+  - Edit category XMLs, not the combined ruleset files.
+  - Register new categories in `categories.properties`.
+- **Test data XML:**
+  - Use `<description>` starting with `violation:` or `no violation:`.
+  - Use class names like `Foo`, method names like `bad`/`good`, and `//bad` comments on flagged lines.
+- **Kotlin rules:**
+  - Complex rules can be implemented as Java classes extending `AbstractKotlinRule`.
+  - Use text comparison for token checks (e.g., `t.getText().equals("+=")`) (this is due to a little bug in pmd-core lib, waiting to be fixed).
+- **Indentation:**
+  - Use spaces only (no tabs).
+
+## Documentation
+
+- Rule documentation is in `docs/` (e.g., `JavaCodePerformance.md`, `JavaCodeQuality.md`, `JavaDataAccessPerformance.md`).
+
+---
+
+Let me know if you want to adjust anything or add coverage for areas I may have missed.

CLAUDE.md

@@ -0,0 +1,92 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+PMD-jPinpoint-rules is a collection of custom PMD static analysis rules for Java and Kotlin, focused on performance, sustainability, multi-threading, data mix-up, and code quality. Rules are implemented as XPath expressions inside XML rule definition files (no custom Java rule classes).
+
+## Commands
+
+### Build and test
+```sh
+mvn clean test       # run all unit tests
+./test               # shorthand script (runs ./mvnw test)
+```
+
+### Run a single test class
+```sh
+mvn test -Dtest=AvoidSpringMVCMemoryLeaksTest
+```
+
+### Merge category XML files into the combined ruleset
+```sh
+./merge              # merges Java categories → rulesets/java/jpinpoint-rules.xml
+./merge kotlin       # merges Kotlin categories → rulesets/kotlin/jpinpoint-kotlin-rules.xml
+```
+The merge step is required after editing any `src/main/resources/category/**/*.xml` file so that the combined `rulesets/` files stay up to date.
+
+## Architecture
+
+### Rule definitions (source of truth)
+Rules live in per-category XML files under `src/main/resources/category/`:
+
+| Language | Category files |
+|----------|---------------|
+| Java | `java/common.xml`, `java/common_std.xml`, `java/concurrent.xml`, `java/enterprise.xml`, `java/remoting.xml`, `java/spring.xml`, `java/sql.xml` |
+| Kotlin | `kotlin/common.xml`, `kotlin/remoting.xml` |
+
+Each category is registered in `src/main/resources/category/{java,kotlin}/categories.properties`.
+
+Most rules use `class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"` — rules are XPath 2.0 queries over the PMD AST. Complex rules that are hard to express in XPath can be implemented as Java classes (see below).
+
+### Combined rulesets (generated)
+`rulesets/java/jpinpoint-rules.xml` and `rulesets/kotlin/jpinpoint-kotlin-rules.xml` are **generated** by the merger tool from the category files. Edit the category files, not these.
+
+### Tests
+Each rule has exactly two files:
+
+1. **Test class** — `src/test/java/com/jpinpoint/perf/lang/{java,kotlin}/ruleset/{category}/{RuleName}Test.java`
+   Always empty except for extending `PmdRuleTst`. The package path encodes the language and category, which PMD uses to locate the rule XML and test data.
+
+2. **Test data** — `src/test/resources/com/jpinpoint/perf/lang/{java,kotlin}/ruleset/{category}/xml/{RuleName}.xml`
+   Contains `<test-code>` blocks with:
+   - `<description>` starting with `violation:` or `no violation:`
+   - `<expected-problems>` (count)
+   - `<expected-linenumbers>`
+   - `<code>` (CDATA) — use class names `Foo`, method names `bad`/`good`, and `//bad` comments on flagged lines
+
+### Merger tool
+`rulesets-merger/src/main/java/com/jpinpoint/perf/tools/RulesetMerger.java` — standalone Maven module that merges category XMLs into the combined ruleset files.
+
+## Adding a New Rule
+
+1. Add the rule definition to the appropriate `src/main/resources/category/{java,kotlin}/{category}.xml`
+2. Create the empty test class in `src/test/java/com/jpinpoint/perf/lang/{java,kotlin}/ruleset/{category}/{RuleName}Test.java`
+3. Create the test data XML in `src/test/resources/com/jpinpoint/perf/lang/{java,kotlin}/ruleset/{category}/xml/{RuleName}.xml`
+4. Document the rule in the appropriate `docs/` markdown file
+5. Run `./merge` to regenerate the combined ruleset
+6. Run `./test` to verify
+
+For a new category, also add an entry to `categories.properties`.
+
+### Java-based Kotlin rules
+
+For complex logic that is hard to express in XPath, rules can be implemented as Java classes:
+
+- **Location**: `src/main/java/com/jpinpoint/perf/lang/kotlin/rule/{category}/{RuleName}Rule.java`
+- **Pattern**: extend `AbstractKotlinRule`, override `buildTargetSelector()` and `buildVisitor()`
+- **Visitor**: inner class extending `KotlinVisitorBase<RuleContext, Void>`, override `visitXxx()` methods
+- **pmd-kotlin dependency**: must be `compile`-scoped (not `test`) so the rule class can import from `net.sourceforge.pmd.lang.kotlin.*`
+- **XML registration**: use `class="com.jpinpoint.perf.lang.kotlin.rule.common.MyRule"` instead of `class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"`; keep `language="kotlin"` attribute
+
+**Key API notes** (PMD 7.x ANTLR-based Kotlin AST):
+- `node.descendants(KtFoo.class)` / `node.ancestors(KtFoo.class)` / `node.children(KtFoo.class)` return `NodeStream<T>`
+- `NodeStream` methods: `.any(Predicate)`, `.filter(Predicate)`, `.first()`, `.toList()`, `.nonEmpty()`, `.isEmpty()`
+- `KotlinTerminalNode.getText()` returns the token image (e.g. `"String"`, `"+="`, `"+"`)
+- **Do NOT use** `node.getToken(type, idx)` or `terminalNode.ADD()` / `terminalNode.ADD_ASSIGNMENT()` style methods — `BaseAntlrTerminalNode.getTokenKind()` returns the token stream index, not the token type, causing these to always return null. Use **text comparison** instead: `t.getText().equals("+=")`
+- Reference implementation in pmd-kotlin jar: `net.sourceforge.pmd.lang.kotlin.rule.errorprone.OverrideBothEqualsAndHashcodeRule`
+
+## Code Style
+
+- Indentation: **spaces only** (no tabs)

pom.xml

@@ -15,9 +15,21 @@
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <spring.version>6.2.10</spring.version>
-        <pmd.version>7.16.0</pmd.version>
+        <pmd.version>7.21.0</pmd.version>
     </properties>
 
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.junit</groupId>
+                <artifactId>junit-bom</artifactId>
+                <version>5.14.2</version>
+                <type>pom</type>
+                <scope>import</scope>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
     <build>
         <plugins>
             <plugin>
@@ -27,19 +39,14 @@
                 <configuration>
                     <source>11</source>
                     <target>11</target>
-                    <!-- no need to compile this project -->
-                    <skipMain>true</skipMain>
                 </configuration>
             </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-surefire-plugin</artifactId>
-                <version>3.5.2</version>
+                <version>3.5.4</version>
                 <configuration>
-                    <includes>
-                        <include>**/kotlin/**</include>
-                        <include>**/java/**</include>
-                    </includes>
+                    <!-- Use Surefire defaults; ensure provider picks up JUnit Platform -->
                 </configuration>
             </plugin>
 
@@ -74,6 +81,18 @@
             <version>${pmd.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>net.sourceforge.pmd</groupId>
+            <artifactId>pmd-lang-test</artifactId>
+            <version>${pmd.version}</version>
+            <scope>test</scope>
+            <exclusions>
+                <exclusion>
+                    <groupId>io.kotest</groupId>
+                    <artifactId>*</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
         <dependency>
             <groupId>net.sourceforge.pmd</groupId>
             <artifactId>pmd-java</artifactId>
@@ -84,12 +103,12 @@
             <groupId>net.sourceforge.pmd</groupId>
             <artifactId>pmd-kotlin</artifactId>
             <version>${pmd.version}</version>
-            <scope>test</scope>
         </dependency>
+        <!-- Hamcrest for assertThat, matchers used in some tests -->
         <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <version>4.13.2</version>
+            <groupId>org.hamcrest</groupId>
+            <artifactId>hamcrest</artifactId>
+            <version>2.2</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -223,12 +242,6 @@
                 <version>1.18.34</version>
                 <!--scope>provided</scope-->
             </dependency>
-        <!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-surefire-plugin -->
-        <dependency>
-            <groupId>org.apache.maven.plugins</groupId>
-            <artifactId>maven-surefire-plugin</artifactId>
-            <version>3.3.1</version>
-        </dependency>
         <!-- https://mvnrepository.com/artifact/io.github.resilience4j/resilience4j-core -->
         <dependency>
             <groupId>io.github.resilience4j</groupId>
@@ -258,14 +271,6 @@
             <version>2.20.0</version>
             <scope>compile</scope>
         </dependency>
-
     </dependencies>
-    <repositories>
-        <repository>
-            <id>maven_central</id>
-            <name>Maven Central</name>
-            <url>https://repo.maven.apache.org/maven2/</url>
-        </repository>
-    </repositories>
+</project>
 
-</project>

rulesets/kotlin/jpinpoint-kotlin-rules.xml

@@ -61,7 +61,7 @@ class Foo {
     </rule>
 
     <rule name="AvoidImplicitlyRecompilingRegex"
-          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
+          class="com.jpinpoint.perf.lang.kotlin.rule.common.AvoidImplicitlyRecompilingRegexRule"
           language="kotlin"
           message="String regex method, Pattern.matches or FileSystem.getPathMatcher is used. Implicitly compiles a regex pattern, can be expensive."
           externalInfoUrl="https://github.com/jborgers/PMD-jPinpoint-rules/tree/pmd7/docs/JavaCodePerformance.md#ireu01">
@@ -71,80 +71,6 @@ class Foo {
         <priority>2</priority>
         <properties>
             <property name="tag" value="jpinpoint-rule" type="String" description="for-sonar"/>
-            <property name="xpath">
-                <value><![CDATA[
-//FunctionDeclaration//PostfixUnaryExpression//SimpleIdentifier/T-Identifier[
-    @Text='Regex'
-    (: not called on fun parameter :)
-    and not(ancestor::PostfixUnaryExpression//CallSuffix//PrimaryExpression//T-Identifier[
-        @Text = ancestor::FunctionDeclaration//FunctionValueParameter//Parameter/SimpleIdentifier/T-Identifier/@Text])
-    (: not called on 'dynamic' function call :)
-    and not(ancestor::PostfixUnaryExpression/PostfixUnarySuffix/CallSuffix//CallSuffix//CallSuffix)
-    (: not if based on local variable initialized by fun parameter :)
-    and not(ancestor::CallSuffix//PostfixUnaryExpression/PrimaryExpression/SimpleIdentifier/T-Identifier[
-        @Text = ancestor::FunctionBody//PropertyDeclaration/VariableDeclaration/SimpleIdentifier/T-Identifier/@Text])
-    (: not param in String template in fun parameter :)
-    and not(../../../../PostfixUnaryExpression//CallSuffix/ValueArguments/ValueArgument//LineStringContent/T-LineStrRef[
-       @Text = ancestor::FunctionDeclaration//Parameter/SimpleIdentifier/T-Identifier/concat('$', @Text)])
-    (: not param in String template of class var field :)
-    and not(../../../../PostfixUnaryExpression//CallSuffix/ValueArguments/ValueArgument//LineStringContent/T-LineStrRef[
-       @Text = ancestor::ClassDeclaration//PropertyDeclaration[T-VAR]//SimpleIdentifier/T-Identifier/concat('$', @Text)])
-    (: not param in String concatenation of class var field :)
-    and not(../../../../PostfixUnaryExpression//CallSuffix/ValueArguments/ValueArgument[//LineStringLiteral]//AdditiveExpression/MultiplicativeExpression//SimpleIdentifier/T-Identifier[
-       @Text = ancestor::ClassDeclaration//PropertyDeclaration[T-VAR]//SimpleIdentifier/T-Identifier/@Text])
-]
-
-|
-
-//FunctionDeclaration//PostfixUnaryExpression/PostfixUnarySuffix/NavigationSuffix/SimpleIdentifier/T-Identifier[
-    @Text='toRegex'
-    (: not called on function parameter :)
-    and not(../../../../PrimaryExpression//T-Identifier[
-        @Text = ancestor::FunctionDeclaration//FunctionValueParameter//Parameter/SimpleIdentifier/T-Identifier/@Text])
-    (: not called on 'dynamic' function call :)
-    and not(ancestor::PostfixUnaryExpression/PostfixUnarySuffix[1]/CallSuffix)
-    (: not if based on local variable initialized by fun parameter :)
-    and not(../../../../../PostfixUnaryExpression/PrimaryExpression/SimpleIdentifier/T-Identifier[
-        @Text = ancestor::FunctionBody//PropertyDeclaration/VariableDeclaration/SimpleIdentifier/T-Identifier/@Text])
-]
-
-|
-
-(: check if java.util.regex.Pattern import exists as filter for same named classes in other packages :)
-//ImportHeader[
-    (.//T-Identifier[@Text='java'] and .//T-Identifier[@Text='util'] and .//T-Identifier[@Text='regex'] and .//T-Identifier[@Text='Pattern'] or .//T-MULT)
-  ][1]/ancestor::KotlinFile
-//SimpleIdentifier/T-Identifier[@Text='Pattern'
-    and ../../../PostfixUnarySuffix//T-Identifier[@Text='matches']
-    (: not if first param is fun parameter :)
-    and not(../../../PostfixUnarySuffix/CallSuffix/ValueArguments/ValueArgument[1]//SimpleIdentifier/T-Identifier[
-        @Text = ancestor::FunctionDeclaration//Parameter/SimpleIdentifier/T-Identifier/@Text])
-]
-
-|
-
-(: check if java.nio.file.FileSystems or java.nio.file.Path imports exists as filter for same named classes in other packages :)
-(: TODO is this a bug: having to use T-FILE for 'file' :)
-//ImportHeader[
-    (.//T-Identifier[@Text='java']
-        and .//T-Identifier[@Text='nio'] and .//T-FILE[@Text='file'] and .//T-Identifier[@Text='FileSystems' or @Text='Path'] or .//T-MULT)
-  ][1]/ancestor::KotlinFile
-(: added [ancestor::NavigationSuffix] to avoid PAT_STRING param from being selected too :)
-//FunctionDeclaration//PostfixUnarySuffix//T-Identifier[ancestor::NavigationSuffix][@Text='getPathMatcher'
-    and (ancestor::PostfixUnaryExpression/PrimaryExpression//T-Identifier[@Text=
-              ancestor::Statement/preceding-sibling::Statement//VariableDeclaration[../Expression//T-Identifier[@Text='FileSystems']]//T-Identifier/@Text]
-         or ancestor::PostfixUnaryExpression/PrimaryExpression/SimpleIdentifier/T-Identifier[@Text='FileSystems']
-
-    )
-    (: not if first param is fun parameter :)
-    and not(ancestor::PrefixUnaryExpression//CallSuffix/ValueArguments/ValueArgument//SimpleIdentifier/T-Identifier[
-       @Text = ancestor::FunctionDeclaration//Parameter/SimpleIdentifier/T-Identifier/@Text])
-    (: not param in String template in fun parameter :)
-    and not(ancestor::PrefixUnaryExpression//CallSuffix/ValueArguments/ValueArgument//LineStringContent/T-LineStrRef[
-       @Text = ancestor::FunctionDeclaration//Parameter/SimpleIdentifier/T-Identifier/concat('$', @Text)])
-]
-                ]]></value>
-            </property>
         </properties>
         <example>
 class Foo {
@@ -218,34 +144,19 @@ class AvoidInMemoryStreamingDefaultConstructor {
         </example>
     </rule>
 
-    <rule name="AvoidMultipleConcatStatements" class="net.sourceforge.pmd.lang.rule.xpath.XPathRule" language="kotlin" message="Multiple statements concatenate to the same String. Use StringBuilder append." externalInfoUrl="https://github.com/jborgers/PMD-jPinpoint-rules/tree/pmd7/docs/JavaCodePerformance.md#isu02">
+    <rule name="AvoidMultipleConcatStatements"
+          language="kotlin"
+          message="Multiple statements concatenate to the same String. Use StringBuilder append."
+          externalInfoUrl="https://github.com/jborgers/PMD-jPinpoint-rules/tree/pmd7/docs/JavaCodePerformance.md#isu02"
+          class="com.jpinpoint.perf.lang.kotlin.rule.common.AvoidMultipleConcatStatementsRule">
         <description>Multiple statements concatenate to the same String. Problem: Each statement with one or more +-operators creates a hidden temporary StringBuilder, a char[] and a new String object, which all have to be garbage collected.&#13;
             Solution: Use StringBuilder.append.
             (jpinpoint-rules)</description>
         <priority>2</priority>
         <properties>
             <property name="tag" value="jpinpoint-rule" type="String" description="for-sonar"/>
-            <property name="xpath">
-                <value><![CDATA[
-//FunctionBody[count(.//Assignment[.//(AssignmentAndOperator/T-ADD_ASSIGNMENT|AdditiveOperator/T-ADD)]/(AssignableExpression|DirectlyAssignableExpression)//T-Identifier[@Text=
-(: property a string literal :)
-ancestor::FunctionBody//PropertyDeclaration[(
-    Expression[not(.//Expression)]//StringLiteral or
-    (: or explicit type String:)
-    VariableDeclaration/Type//T-Identifier[@Text='String'] or
-    (: or assigned parameter of type String :)
-    Expression[.//T-Identifier[@Text = ancestor::FunctionDeclaration/FunctionValueParameters/FunctionValueParameter[Parameter/Type//T-Identifier[@Text='String']]//T-Identifier/@Text]] or
-    (: or assigned non-nested function of explicit type String :) (: known issue: ignores parameters, may give false positives with overloaded methods :)
-    Expression[.//T-Identifier[not(ancestor::CallSuffix)][@Text = ancestor::ClassMemberDeclarations//FunctionDeclaration[Type//T-Identifier[@Text='String']]//T-Identifier/@Text]]
-)]
-/VariableDeclaration//T-Identifier/@Text]) > 1]
-//Statement[Assignment//(T-ADD_ASSIGNMENT|T-ADD)][position()=last()]
-
-	]]></value>
-            </property>
         </properties>
         <example>
-
         </example>
     </rule>