Merge branch 'pr-1520'

docs/pages/release_notes.md

@@ -14,6 +14,13 @@ This is a {{ site.pmd.release_type }} release.
 
 ### New and noteworthy
 
+#### New Rules
+
+*   The new Java rule {% rule "java/bestpractices/ForLoopVariableCount" %} (`java-bestpractices`) checks for
+    the number of control variables in a for-loop. Having a lot of control variables makes it harder to understand
+    what the loop does. The maximum allowed number of variables is by default 1 and can be configured by a
+    property.
+
 #### Modified Rules
 
 *   The Java rule {% rule "java/codestyle/LocalVariableCouldBeFinal" %} (`java-codestyle`) has a new
@@ -24,6 +31,7 @@ This is a {{ site.pmd.release_type }} release.
 
 *   java-bestpractices
     *   [#658](https://github.com/pmd/pmd/issues/658): \[java] OneDeclarationPerLine: False positive for loops
+    *   [#1519](https://github.com/pmd/pmd/issues/1519): \[java] New rule: ForLoopVariableCount
 *   java-codestyle
     *   [#1513](https://github.com/pmd/pmd/issues/1513): \[java] LocalVariableCouldBeFinal: allow excluding the variable in a for-each loop
 *   java-errorprone
@@ -40,6 +48,7 @@ This is a {{ site.pmd.release_type }} release.
 *   [#1503](https://github.com/pmd/pmd/pull/1503): \[java] Fix for ReturnFromFinallyBlock false-positives - [RishabhDeep Singh](https://github.com/rishabhdeepsingh)
 *   [#1514](https://github.com/pmd/pmd/pull/1514): \[java] LocalVariableCouldBeFinal: allow excluding the variable in a for-each loop - [Kris Scheibe](https://github.com/kris-scheibe)
 *   [#1516](https://github.com/pmd/pmd/pull/1516): \[java] OneDeclarationPerLine: Don't report multiple variables in a for statement. - [Kris Scheibe](https://github.com/kris-scheibe)
+*   [#1520](https://github.com/pmd/pmd/pull/1520): \[java] New rule: ForLoopVariableCount: check the number of control variables in a for loop - [Kris Scheibe](https://github.com/kris-scheibe)
 *   [#1521](https://github.com/pmd/pmd/pull/1521): \[java] Upgrade to ASM7 for JDK 11 support - [Mark Pritchard](https://github.com/markpritchard)
 
 {% endtocmaker %}

pmd-java/src/main/resources/category/java/bestpractices.xml

@@ -382,6 +382,33 @@ public class MyClass {
         </example>
     </rule>
 
+    <rule name="ForLoopVariableCount"
+          language="java"
+          since="6.11.0"
+          message="Too many control variables in the 'for' statement"
+          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          externalInfoUrl="${pmd.website.baseurl}/pmd_rules_java_codestyle.html#forloopvariablecount">
+        <description>
+Having a lot of control variables in a 'for' loop makes it harder to see what range of values
+the loop iterates over. By default this rule allows a regular 'for' loop with only one variable.
+        </description>
+        <priority>3</priority>
+        <properties>
+            <property name="maximumVariables" type="Integer"
+                      description="A regular for statement will have 1 control variable" min="0" max="100" value="1"/>
+            <property name="xpath">
+                <value>//ForInit/LocalVariableDeclaration[count(VariableDeclarator) > $maximumVariables]</value>
+            </property>
+        </properties>
+        <example>
+<![CDATA[
+// this will be reported with the default setting of at most one control variable in a for loop
+for (int i = 0, j = 0; i < 10; i++, j += 2) {
+   foo();
+]]>
+        </example>
+    </rule>
+
     <rule name="GuardLogStatement"
           language="java"
           since="5.1.0"

pmd-java/src/main/resources/category/java/codestyle.xml

@@ -787,7 +787,6 @@ for (int i = 0; i < 42; i++)
         </example>
     </rule>
 
-
     <rule name="FormalParameterNamingConventions"
           since="6.6.0"
           message="The {0} name ''{1}'' doesn''t match ''{2}''"

pmd-java/src/test/java/net/sourceforge/pmd/lang/java/rule/bestpractices/ForLoopVariableCountTest.java

@@ -0,0 +1,11 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.java.rule.bestpractices;
+
+import net.sourceforge.pmd.testframework.PmdRuleTst;
+
+public class ForLoopVariableCountTest extends PmdRuleTst {
+    // no additional unit tests
+}

pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/bestpractices/xml/ForLoopVariableCount.xml

@@ -0,0 +1,74 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<test-data
+        xmlns="http://pmd.sourceforge.net/rule-tests"
+        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:schemaLocation="http://pmd.sourceforge.net/rule-tests http://pmd.sourceforge.net/rule-tests_1_0_0.xsd">
+    <test-code>
+        <description>default: valid case</description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+            public class Foo {
+                void foo() {
+                    for (int i=0; i<42; i++) {
+                        foo();
+                    }
+                }
+            }
+        ]]></code>
+    </test-code>
+    <test-code>
+        <description>default: failing case</description>
+        <expected-problems>1</expected-problems>
+        <code><![CDATA[
+            public class Foo {
+                void foo() {
+                    for (int i=0, j=0; i<42; i++, j++) {
+                        foo();
+                    }
+                }
+            }
+        ]]></code>
+    </test-code>
+    <test-code>
+        <description>custom count: valid case</description>
+        <rule-property name="maximumVariables">2</rule-property>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+            public class Foo {
+                void foo() {
+                    for (int i=0, j=0; i<42; i++, j++) {
+                        foo();
+                    }
+                }
+            }
+        ]]></code>
+    </test-code>
+    <test-code>
+        <description>custom count: valid (but useless) case</description>
+        <rule-property name="maximumVariables">0</rule-property>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+            public class Foo {
+                void foo() {
+                    for (;;) {
+                        foo();
+                    }
+                }
+            }
+        ]]></code>
+    </test-code>
+    <test-code>
+        <description>custom count: failing case</description>
+        <rule-property name="maximumVariables">2</rule-property>
+        <expected-problems>1</expected-problems>
+        <code><![CDATA[
+            public class Foo {
+                void foo() {
+                    for (int i=0, j=0, k=0; i<42; i++, j++, k++) {
+                        foo();
+                    }
+                }
+            }
+        ]]></code>
+    </test-code>
+</test-data>