Issue #461: Field single declaration check implemented

eclipsecs-sevntu-plugin/src/com/github/sevntu/checkstyle/checks/coding/checkstyle-metadata.properties

@@ -43,6 +43,10 @@ EmptyPublicCtorInClassCheck.desc = <p>This Check looks for useless empty public
 EmptyPublicCtorInClassCheck.classAnnotationNames = Regex which matches names of class annotations which require class to have public no-argument ctor. Default value is "javax\\.persistence\\.Entity".
 EmptyPublicCtorInClassCheck.ctorAnnotationNames = Regex which matches names of ctor annotations which make empty public ctor essential. Default value is "com\\.google\\.inject\\.Inject".
 
+FieldSingleDeclarationCheck.name = Field Single Declaration Check
+FieldSingleDeclarationCheck.desc = <p>This checks ensures that classes have at most 1 field of the given className. This can be useful for example to ensure that only one Logger is used.</p>
+FieldSingleDeclarationCheck.fullyQualifiedClassName = Fully qualified name of class of which there should only be max. 1 field per class. Example: "org.slf4j.Logger".
+
 FinalizeImplementationCheck.name = Finalize Implementation
 FinalizeImplementationCheck.desc = <p>This Check detects 3 most common cases of incorrect finalize() method implementation:</p><ul><li>negates effect of superclass finalize<br/><code>protected void finalize() { } <br/> protected void finalize() { doSomething(); }</code></li><li>useless (or worse) finalize<br/><code>protected void finalize() { super.finalize(); }</code></li><li>public finalize<br/><code>public void finalize() { try { doSomething(); } finally { super.finalize() } }</code></li></ul>
 

eclipsecs-sevntu-plugin/src/com/github/sevntu/checkstyle/checks/coding/checkstyle-metadata.xml

@@ -162,6 +162,17 @@
  <message-key key="empty.public.ctor"/>
  </rule-metadata>
 
+ <rule-metadata name="%FieldSingleDeclarationCheck.name" internal-name="FieldSingleDeclarationCheck" parent="TreeWalker">
+ <alternative-name internal-name="com.github.sevntu.checkstyle.checks.coding.FieldSingleDeclarationCheck"/>
+ <description>%FieldSingleDeclarationCheck.desc</description>
+
+ <property-metadata name="fullyQualifiedClassName" datatype="String" default-value="java.util.logging.Logger">
+ <description>%FieldSingleDeclarationCheck.fullyQualifiedClassName</description>
+ </property-metadata>
+
+ <message-key key="field.count"/>
+ </rule-metadata>
+
  <rule-metadata name="%ForbidCertainImportsCheck.name" internal-name="ForbidCertainImportsCheck" parent="TreeWalker">
  <alternative-name internal-name="com.github.sevntu.checkstyle.checks.coding.ForbidCertainImportsCheck"/>
  <description>%ForbidCertainImportsCheck.desc</description>

sevntu-checks/sevntu-checks.xml

@@ -152,6 +152,9 @@
  <property name="ignoreFieldNamePattern" value="serialVersionUID"/>
  </module>
  <module name="com.github.sevntu.checkstyle.checks.coding.EmptyPublicCtorInClassCheck"/>
+ <module name="com.github.sevntu.checkstyle.checks.coding.FieldSingleDeclarationCheck">
+ <property name="fullyQualifiedClassName" value="java.util.logging.Logger"/>
+ </module>
  <module name="com.github.sevntu.checkstyle.checks.coding.DiamondOperatorForVariableDefinitionCheck"/>
  <module name="com.github.sevntu.checkstyle.checks.coding.NameConventionForJunit4TestClassesCheck"/>
  <module name="com.github.sevntu.checkstyle.checks.coding.UselessSuperCtorCallCheck"/>

sevntu-checks/src/main/java/com/github/sevntu/checkstyle/SevntuUtil.java

@@ -21,6 +21,9 @@
 
 import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
 import com.puppycrawl.tools.checkstyle.api.DetailAST;
+import com.puppycrawl.tools.checkstyle.api.FullIdent;
+import com.puppycrawl.tools.checkstyle.api.TokenTypes;
+import com.puppycrawl.tools.checkstyle.utils.CheckUtil;
 import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
 
 /**
@@ -76,4 +79,40 @@ public static DetailAST getNextSubTreeNode(DetailAST node, DetailAST subTreeRoot
  return toVisitAst;
  }
 
+ /**
+ * Obtains full type name of first token in node.
+ * @param ast an AST node
+ * @return fully qualified name (FQN) of type, or null if none was found
+ */
+ public static String getTypeNameOfFirstToken(DetailAST ast) {
+ final DetailAST findFirstToken = ast.findFirstToken(TokenTypes.TYPE);
+ final FullIdent ident = CheckUtil.createFullType(findFirstToken);
+
+ return ident.getText();
+ }
+
+ /**
+ * Checks node for matching class, taken both FQN and short name into account.
+ *
+ * @param ast
+ * an AST node
+ * @param fqClassName
+ * fully qualified class name
+ * @return true if type name of first token in node is fqnClassName, or its short name; false
+ * otherwise
+ */
+ public static boolean matchesFullyQualifiedName(DetailAST ast, String fqClassName) {
+ final String typeName = getTypeNameOfFirstToken(ast);
+ final int lastDotPosition = fqClassName.lastIndexOf('.');
+ boolean isMatched = false;
+ if (lastDotPosition == -1) {
+ isMatched = typeName.equals(fqClassName);
+ }
+ else {
+ final String shortClassName = fqClassName.substring(lastDotPosition + 1);
+ isMatched = typeName.equals(fqClassName) || typeName.equals(shortClassName);
+ }
+ return isMatched;
+ }
+
 }

sevntu-checks/src/main/java/com/github/sevntu/checkstyle/checks/coding/FieldSingleDeclarationCheck.java

@@ -0,0 +1,108 @@
+////////////////////////////////////////////////////////////////////////////////
+// checkstyle: Checks Java source code for adherence to a set of rules.
+// Copyright (C) 2001-2020 the original author or authors.
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+////////////////////////////////////////////////////////////////////////////////
+
+package com.github.sevntu.checkstyle.checks.coding;
+
+import com.github.sevntu.checkstyle.SevntuUtil;
+import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
+import com.puppycrawl.tools.checkstyle.api.DetailAST;
+import com.puppycrawl.tools.checkstyle.api.TokenTypes;
+
+/**
+ * <p>This checks ensures that classes have at most 1 field of the given className.</p>
+ *
+ * <p>This can be useful for example to ensure that only one Logger is used:</p>
+ *
+ * <pre>
+ * &lt;module name="TreeWalker"&gt;
+ * &lt;module name="com.github.sevntu.checkstyle.checks.coding.FieldSingleDeclarationCheck"&gt;
+ * &lt;property name="fullyQualifiedClassName" value="org.slf4j.Logger" /&gt;
+ * &lt;/module&gt;
+ * &lt;/module&gt;
+ *
+ * class Example {
+ * private static final org.slf4j.Logger logger = LoggerFactory.getLogger(Example.class); // OK
+ * private static org.slf4j.Logger logger2; // NOK!
+ * }
+ * </pre>
+ *
+ * @author Milos Fabian, Pantheon Technologies - original author (in OpenDaylight.org)
+ * @author Michael Vorburger.ch - refactored and made more generalized for contribution to Sevntu
+ * @author <a href="mailto:[email protected]">Yasser Aziza</a> - completed sevntu integration
+ */
+public class FieldSingleDeclarationCheck extends AbstractCheck {
+
+ /**
+ * Violation message key.
+ */
+ public static final String MSG_KEY = "field.count";
+
+ /**
+ * Configuration property with class name check for.
+ */
+ private String fullyQualifiedClassName;
+
+ /**
+ * Field to remember if class was previously seen in current File.
+ */
+ private boolean hasPreviouslySeenClass;
+
+ /**
+ * Set Class of which there should only be max. 1 field per class.
+ * @param className the fully qualified name (FQN) of the class
+ */
+ public void setFullyQualifiedClassName(String className) {
+ this.fullyQualifiedClassName = className;
+ }
+
+ @Override
+ public int[] getDefaultTokens() {
+ return new int[] {TokenTypes.VARIABLE_DEF };
+ }
+
+ @Override
+ public int[] getRequiredTokens() {
+ return getDefaultTokens();
+ }
+
+ @Override
+ public int[] getAcceptableTokens() {
+ return getDefaultTokens();
+ }
+
+ @Override
+ public void beginTree(DetailAST rootAST) {
+ this.hasPreviouslySeenClass = false;
+ }
+
+ @Override
+ public void visitToken(DetailAST ast) {
+ if (fullyQualifiedClassName == null) {
+ throw new IllegalStateException("Must set mandatory fullyQualifiedClassName property in"
+ + getClass().getSimpleName());
+ }
+ if (SevntuUtil.matchesFullyQualifiedName(ast, fullyQualifiedClassName)) {
+ if (hasPreviouslySeenClass) {
+ log(ast.getLineNo(), MSG_KEY, fullyQualifiedClassName);
+ }
+ this.hasPreviouslySeenClass = true;
+ }
+ }
+
+}

sevntu-checks/src/main/resources/com/github/sevntu/checkstyle/checks/coding/messages.properties

@@ -14,6 +14,7 @@ custom.declaration.order.method=Method definition in wrong order. Expected ''{0}
 diamond.operator.for.variable.definition=Diamond operator expected.
 either.log.or.throw=Either log or throw exception.
 empty.public.ctor=This empty public constructor is useless.
+field.count={0} should be declared only once.
 finalize.implementation.missed.super.finalize=You have to call super.finalize() right after finally opening brace.
 finalize.implementation.missed.try.finally=finalize() method should contain try-finally block with super.finalize() call inside finally block.
 finalize.implementation.public=finalize() method should have a "protected" visibility.

sevntu-checks/src/test/java/com/github/sevntu/checkstyle/checks/coding/FieldSingleDeclarationCheckTest.java

@@ -0,0 +1,103 @@
+////////////////////////////////////////////////////////////////////////////////
+// checkstyle: Checks Java source code for adherence to a set of rules.
+// Copyright (C) 2001-2020 the original author or authors.
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+////////////////////////////////////////////////////////////////////////////////
+
+package com.github.sevntu.checkstyle.checks.coding;
+
+import org.junit.Test;
+
+import com.puppycrawl.tools.checkstyle.AbstractModuleTestSupport;
+import com.puppycrawl.tools.checkstyle.DefaultConfiguration;
+import com.puppycrawl.tools.checkstyle.api.CheckstyleException;
+
+/**
+ * LoggerDeclarationsCountCheck test.
+ *
+ * @author <a href="mailto:[email protected]">Michael Vorburger</a> - completed sevntu integration
+ */
+public class FieldSingleDeclarationCheckTest extends AbstractModuleTestSupport {
+
+ private static final String CLASS_NAME_KEY = "fullyQualifiedClassName";
+ private static final String CLASS_NAME_VALUE = "org.slf4j.Logger";
+
+ private final DefaultConfiguration checkConfig =
+ createModuleConfig(FieldSingleDeclarationCheck.class);
+
+ @Override
+ protected String getPackageLocation() {
+ return "com/github/sevntu/checkstyle/checks/coding";
+ }
+
+ @Test
+ public void testFieldSingleDeclarationOk() throws Exception {
+ checkConfig.addAttribute(CLASS_NAME_KEY, CLASS_NAME_VALUE);
+
+ verify(checkConfig, getPath("InputFieldSingleDeclarationCheckOk.java"), new String[] {});
+ }
+
+ @Test
+ public void testFieldSingleDeclarationNok() throws Exception {
+ checkConfig.addAttribute(CLASS_NAME_KEY, CLASS_NAME_VALUE);
+
+ final String[] expected = {
+ "10: " + getCheckMessage(FieldSingleDeclarationCheck.MSG_KEY, CLASS_NAME_VALUE),
+ };
+
+ verify(checkConfig, getPath("InputFieldSingleDeclarationCheckNok.java"), expected);
+ verify(checkConfig, getPath("InputFieldSingleDeclarationCheckOk.java"), new String[] {});
+ }
+
+ @Test
+ public void testFieldSingleDeclarationFqnNok() throws Exception {
+ checkConfig.addAttribute(CLASS_NAME_KEY, CLASS_NAME_VALUE);
+
+ final String[] expected = {
+ "7: " + getCheckMessage(FieldSingleDeclarationCheck.MSG_KEY, CLASS_NAME_VALUE),
+ };
+
+ verify(checkConfig, getPath("InputFieldSingleDeclarationCheckFqnNok.java"), expected);
+ verify(checkConfig, getPath("InputFieldSingleDeclarationCheckOk.java"), new String[] {});
+ }
+
+ @Test(expected = CheckstyleException.class)
+ public void testNoClassNameConfigured() throws Exception {
+ verify(checkConfig, getPath("InputFieldSingleDeclarationCheckOk.java"), new String[] {});
+ }
+
+ @Test
+ public void testCustomTokens() throws Exception {
+ checkConfig.addAttribute(CLASS_NAME_KEY, CLASS_NAME_VALUE);
+ // This is required just so that getAcceptableTokens() gets coverage
+ checkConfig.addAttribute("tokens", "VARIABLE_DEF");
+
+ verify(checkConfig, getPath("InputFieldSingleDeclarationCheckOk.java"), new String[] {});
+ }
+
+ @Test
+ public void testUnknownClassName() throws Exception {
+ checkConfig.addAttribute(CLASS_NAME_KEY, "logger");
+ // This is required just so that getAcceptableTokens() gets coverage
+ checkConfig.addAttribute("tokens", "VARIABLE_DEF");
+
+ verify(checkConfig, getPath("InputFieldSingleDeclarationCheckOk.java"), new String[] {});
+ verify(checkConfig, getPath("InputFieldSingleDeclarationCheckNok.java"), new String[] {});
+ verify(checkConfig, getPath("InputFieldSingleDeclarationCheckFqnNok.java"),
+ new String[] {});
+ }
+
+}

sevntu-checks/src/test/resources/com/github/sevntu/checkstyle/checks/coding/InputFieldSingleDeclarationCheckFqnNok.java

@@ -0,0 +1,9 @@
+package com.github.sevntu.checkstyle.checks.coding;
+
+public class InputFieldSingleDeclarationCheckFqnNok {
+
+ // even twice a FQN type names work:
+ org.slf4j.Logger logger1;
+ org.slf4j.Logger logger2; // <= Checkstyle violation raised here!
+
+}

sevntu-checks/src/test/resources/com/github/sevntu/checkstyle/checks/coding/InputFieldSingleDeclarationCheckNok.java

@@ -0,0 +1,18 @@
+package com.github.sevntu.checkstyle.checks.coding;
+
+import java.io.File;
+import java.util.logging.Logger;
+
+public class InputFieldSingleDeclarationCheckNok {
+
+ // both FQN and import'ed type names work:
+ Logger logger1;
+ org.slf4j.Logger logger2; // <= Checkstyle violation raised here!
+
+ // some field of another type (req. for test coverage)
+ File file;
+
+ // a method, so that there are not only fields here (req. for test coverage)
+ void foo() { }
+
+}

sevntu-checks/src/test/resources/com/github/sevntu/checkstyle/checks/coding/InputFieldSingleDeclarationCheckOk.java

@@ -0,0 +1,7 @@
+package com.github.sevntu.checkstyle.checks.coding;
+
+public class InputFieldSingleDeclarationCheckOk {
+
+ org.slf4j.Logger logger;
+
+}

sevntu-checkstyle-sonar-plugin/src/main/resources/com/github/sevntu/checkstyle/sonar/checkstyle-extensions.xml

@@ -346,6 +346,19 @@
  </param>
  </rule>
 
+ <rule>
+ <key>com.github.sevntu.checkstyle.checks.coding.FieldSingleDeclarationCheck</key>
+ <name>Field Single Declaration Check</name>
+ <tag>coding</tag>
+ <description>This checks ensures that classes have at most 1 field of the given className. This can be useful for example to ensure that only one Logger is used.</description>
+ <configKey>Checker/TreeWalker/com.github.sevntu.checkstyle.checks.coding.FieldSingleDeclarationCheck</configKey>
+
+ <param key="fullyQualifiedClassName" type="STRING">
+ <defaultValue>java.util.logging.Logger</defaultValue>
+ <description>Fully qualified name of class of which there should only be max. 1 field per class. Example: "java.util.logging.Logger".</description>
+ </param>
+ </rule>
+
  <rule>
  <key>com.github.sevntu.checkstyle.checks.coding.FinalizeImplementationCheck</key>
  <name>Finalize Implementation Check</name>

sevntu-checkstyle-sonar-plugin/src/test/java/com/github/sevntu/checkstyle/sonar/CheckstyleExtensionRulesDefinitionTest.java

@@ -40,7 +40,7 @@ public void testAllRulesValid() {
  Assert.assertEquals("Incorrect repository language", "java", repository.language());
 
  final List<RulesDefinition.Rule> rules = repository.rules();
- Assert.assertEquals("Incorrect number of loaded rules", 59, rules.size());
+ Assert.assertEquals("Incorrect number of loaded rules", 60, rules.size());
 
  for (RulesDefinition.Rule rule : rules) {
  Assert.assertNotNull("Rule key is not set", rule.key());