Add static rule for Unused class fields

scan-command/src/main/java/io/ballerina/scan/internal/CoreRule.java

@@ -32,8 +32,7 @@
 enum CoreRule {
 
     AVOID_CHECKPANIC(RuleFactory.createRule(1, "Avoid checkpanic", RuleKind.CODE_SMELL)),
-    UNUSED_FUNCTION_PARAMETER(RuleFactory.createRule(2,
-            "Unused function parameter", RuleKind.CODE_SMELL)),
+    UNUSED_FUNCTION_PARAMETER(RuleFactory.createRule(2, "Unused function parameter", RuleKind.CODE_SMELL)),
     PUBLIC_NON_ISOLATED_FUNCTION_CONSTRUCT(RuleFactory.createRule(3,
             "Non isolated public function", RuleKind.CODE_SMELL)),
     PUBLIC_NON_ISOLATED_METHOD_CONSTRUCT(RuleFactory.createRule(4,
@@ -49,7 +48,9 @@ enum CoreRule {
     OPERATION_ALWAYS_EVALUATES_TO_SELF_VALUE(RuleFactory.createRule(9,
             "This operation always evaluates to the same value", RuleKind.CODE_SMELL)),
     SELF_ASSIGNMENT(RuleFactory.createRule(10,
-            "This variable is assigned to itself", RuleKind.CODE_SMELL));
+            "This variable is assigned to itself", RuleKind.CODE_SMELL)),
+    UNUSED_PRIVATE_CLASS_FIELD(RuleFactory.createRule(11,
+            "Unused class private fields", RuleKind.CODE_SMELL));
 
     private final Rule rule;
 

scan-command/src/main/java/io/ballerina/scan/internal/StaticCodeAnalyzer.java

@@ -19,6 +19,7 @@
 package io.ballerina.scan.internal;
 
 import io.ballerina.compiler.api.SemanticModel;
+import io.ballerina.compiler.api.symbols.ClassFieldSymbol;
 import io.ballerina.compiler.api.symbols.ObjectTypeSymbol;
 import io.ballerina.compiler.api.symbols.Qualifier;
 import io.ballerina.compiler.api.symbols.Symbol;
@@ -40,6 +41,7 @@
 import io.ballerina.compiler.syntax.tree.Node;
 import io.ballerina.compiler.syntax.tree.NodeList;
 import io.ballerina.compiler.syntax.tree.NodeVisitor;
+import io.ballerina.compiler.syntax.tree.ObjectFieldNode;
 import io.ballerina.compiler.syntax.tree.SimpleNameReferenceNode;
 import io.ballerina.compiler.syntax.tree.SyntaxKind;
 import io.ballerina.compiler.syntax.tree.SyntaxTree;
@@ -52,6 +54,7 @@
 import java.util.List;
 import java.util.Optional;
 
+import static io.ballerina.compiler.syntax.tree.SyntaxKind.PRIVATE_KEYWORD;
 import static io.ballerina.compiler.syntax.tree.SyntaxKind.ISOLATED_KEYWORD;
 import static io.ballerina.compiler.syntax.tree.SyntaxKind.PUBLIC_KEYWORD;
 import static io.ballerina.scan.utils.Constants.INIT_FUNCTION;
@@ -92,9 +95,23 @@ public void visit(CheckExpressionNode checkExpressionNode) {
         if (checkExpressionNode.checkKeyword().kind().equals(SyntaxKind.CHECKPANIC_KEYWORD)) {
             reportIssue(checkExpressionNode, CoreRule.AVOID_CHECKPANIC);
         }
+        this.visitSyntaxNode(checkExpressionNode);
     }
 
     @Override
+    public void visit(ObjectFieldNode objectFieldNode) {
+        semanticModel.symbol(objectFieldNode).ifPresent(symbol -> {
+            if (symbol instanceof ClassFieldSymbol classFieldSymbol) {
+                List<Qualifier> qualifiers = classFieldSymbol.qualifiers();
+                if (hasQualifier(qualifiers, PRIVATE_KEYWORD)) {
+                    if (semanticModel.references(symbol).size() == 1) {
+                        reportIssue(objectFieldNode, CoreRule.UNUSED_PRIVATE_CLASS_FIELD);
+                    }
+                }
+            }
+        });
+        this.visitSyntaxNode(objectFieldNode);
+    }
     public void visit(BinaryExpressionNode binaryExpressionNode) {
         reportIssuesWithTrivialOperations(binaryExpressionNode);
         filterSameReferenceIssueBasedOnOperandType(binaryExpressionNode.operator()).ifPresent(rule -> {
@@ -397,7 +414,7 @@ private boolean isUnusedNode(Node node) {
         Optional<Symbol> symbol = semanticModel.symbol(node);
         return symbol.filter(value -> semanticModel.references(value).size() == 1).isPresent();
     }
-
+    
     private boolean isPublicIsolatedConstruct(NodeList<Token> qualifiers) {
         return hasQualifier(qualifiers, PUBLIC_KEYWORD) && !hasQualifier(qualifiers, ISOLATED_KEYWORD);
     }

scan-command/src/test/java/io/ballerina/scan/internal/CoreRuleTest.java

@@ -47,7 +47,7 @@ public class CoreRuleTest {
 
     @Test(description = "test all rules")
     void testAllRules() {
-        Assert.assertEquals(CoreRule.rules().size(), 10);
+        Assert.assertEquals(CoreRule.rules().size(), 11);
     }
 
     @Test(description = "test checkpanic rule")
@@ -68,6 +68,14 @@ void testUnusedFunctionParameterRule() {
         Assert.assertEquals(rule.kind(), RuleKind.CODE_SMELL);
     }
 
+    @Test(description = "test unused class fields rule")
+    void testUnusedClassFieldsRule() {
+        Rule rule = CoreRule.UNUSED_PRIVATE_CLASS_FIELD.rule();
+        Assert.assertEquals(rule.id(), "ballerina:11");
+        Assert.assertEquals(rule.numericId(), 11);
+        Assert.assertEquals(rule.description(), "Unused class private fields");
+    }
+
     @Test(description = "test always true evaluates")
     void testTrueEvaluates() {
         Rule rule = CoreRule.OPERATION_ALWAYS_EVALUATES_TO_TRUE.rule();

scan-command/src/test/java/io/ballerina/scan/internal/Rule011Test.java

@@ -0,0 +1,57 @@
+/*
+ *  Copyright (c) 2024, WSO2 LLC. (https://www.wso2.com).
+ *
+ *  WSO2 LLC. licenses this file to you under the Apache License,
+ *  Version 2.0 (the "License"); you may not use this file except
+ *  in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied. See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package io.ballerina.scan.internal;
+
+import io.ballerina.projects.Document;
+import io.ballerina.scan.Issue;
+import io.ballerina.scan.RuleKind;
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+import java.util.List;
+
+/**
+ * Unused private class fields analyzer tests.
+ *
+ * @since 0.5.0
+ */
+public class Rule011Test extends StaticCodeAnalyzerTest {
+    private static final String UNUSED_CLASS_PRIVATE_FIELDS = "Unused class private fields";
+
+    @Test(description = "test unused private class fields")
+    void testUnusedPrivateFieldsAnalyzer() {
+        String documentName = "rule011_unused_class_fields.bal";
+        Document document = loadDocument(documentName);
+        ScannerContextImpl scannerContext = new ScannerContextImpl(List.of(CoreRule.UNUSED_PRIVATE_CLASS_FIELD.rule()));
+        StaticCodeAnalyzer staticCodeAnalyzer = new StaticCodeAnalyzer(document, scannerContext,
+                document.module().getCompilation().getSemanticModel());
+        staticCodeAnalyzer.analyze();
+        List<Issue> issues = scannerContext.getReporter().getIssues();
+        Assert.assertEquals(issues.size(), 5);
+        assertIssue(issues.get(0), documentName, 17, 4, 17, 26, "ballerina:11", 11,
+                UNUSED_CLASS_PRIVATE_FIELDS, RuleKind.CODE_SMELL);
+        assertIssue(issues.get(1), documentName, 23, 4, 23, 26, "ballerina:11", 11,
+                UNUSED_CLASS_PRIVATE_FIELDS, RuleKind.CODE_SMELL);
+        assertIssue(issues.get(2), documentName, 31, 4, 31, 30, "ballerina:11", 11,
+                UNUSED_CLASS_PRIVATE_FIELDS, RuleKind.CODE_SMELL);
+        assertIssue(issues.get(3), documentName, 33, 4, 33, 30, "ballerina:11", 11,
+                UNUSED_CLASS_PRIVATE_FIELDS, RuleKind.CODE_SMELL);
+        assertIssue(issues.get(4), documentName, 75, 4, 75, 26, "ballerina:11", 11,
+                UNUSED_CLASS_PRIVATE_FIELDS, RuleKind.CODE_SMELL);
+    }
+}

scan-command/src/test/resources/command-outputs/unix/list-rules-output.txt

@@ -11,6 +11,7 @@ Loading scan tool configurations from src/test/resources/test-resources/bal-proj
 	ballerina:8                                      | CODE_SMELL    | This operation always evaluates to false
 	ballerina:9                                      | CODE_SMELL    | This operation always evaluates to the same value
 	ballerina:10                                     | CODE_SMELL    | This variable is assigned to itself
+	ballerina:11                                     | CODE_SMELL    | Unused class private fields
 	ballerina/example_module_static_code_analyzer:1  | CODE_SMELL    | rule 1
 	ballerina/example_module_static_code_analyzer:2  | BUG           | rule 2
 	ballerina/example_module_static_code_analyzer:3  | VULNERABILITY | rule 3

scan-command/src/test/resources/command-outputs/unix/print-rules-to-console.txt

@@ -11,6 +11,7 @@ Loading scan tool configurations from src/test/resources/test-resources/bal-proj
 	ballerina:8                                      | CODE_SMELL    | This operation always evaluates to false
 	ballerina:9                                      | CODE_SMELL    | This operation always evaluates to the same value
 	ballerina:10                                     | CODE_SMELL    | This variable is assigned to itself
+	ballerina:11                                     | CODE_SMELL    | Unused class private fields
 	ballerina/example_module_static_code_analyzer:1  | CODE_SMELL    | rule 1
 	ballerina/example_module_static_code_analyzer:2  | BUG           | rule 2
 	ballerina/example_module_static_code_analyzer:3  | VULNERABILITY | rule 3

scan-command/src/test/resources/command-outputs/windows/list-rules-output.txt

@@ -11,6 +11,7 @@ Loading scan tool configurations from src\test\resources\test-resources\bal-proj
 	ballerina:8                                      | CODE_SMELL    | This operation always evaluates to false
 	ballerina:9                                      | CODE_SMELL    | This operation always evaluates to the same value
 	ballerina:10                                     | CODE_SMELL    | This variable is assigned to itself
+	ballerina:11                                     | CODE_SMELL    | Unused class private fields
 	ballerina/example_module_static_code_analyzer:1  | CODE_SMELL    | rule 1
 	ballerina/example_module_static_code_analyzer:2  | BUG           | rule 2
 	ballerina/example_module_static_code_analyzer:3  | VULNERABILITY | rule 3

scan-command/src/test/resources/command-outputs/windows/print-rules-to-console.txt

@@ -11,6 +11,7 @@ Loading scan tool configurations from src\test\resources\test-resources\bal-proj
 	ballerina:8                                      | CODE_SMELL    | This operation always evaluates to false
 	ballerina:9                                      | CODE_SMELL    | This operation always evaluates to the same value
 	ballerina:10                                     | CODE_SMELL    | This variable is assigned to itself
+	ballerina:11                                     | CODE_SMELL    | Unused class private fields
 	ballerina/example_module_static_code_analyzer:1  | CODE_SMELL    | rule 1
 	ballerina/example_module_static_code_analyzer:2  | BUG           | rule 2
 	ballerina/example_module_static_code_analyzer:3  | VULNERABILITY | rule 3

scan-command/src/test/resources/test-resources/core-rules/rule011_unused_class_fields.bal

@@ -0,0 +1,87 @@
+// Copyright (c) 2024, WSO2 LLC. (https://www.wso2.com).
+//
+// WSO2 Inc. licenses this file to you under the Apache License,
+// Version 2.0 (the "License"); you may not use this file except
+// in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+class A {
+    private string c = ""; // warning
+}
+
+public isolated class A2 {
+    int a = 1;
+    public string b = "";
+    private string c = ""; // warning
+}
+
+public isolated class A3 {
+    int a;
+    public string b;
+    private string c;
+    private boolean d = true;
+    private boolean? e = true; // warning
+    private int|boolean f = 0;
+    private boolean g = false; // warning
+    public string h = "";
+
+    function init() {
+        self.a = 0;
+        self.b = "";
+        self.c = "";
+    }
+
+    public isolated function test(boolean d) {
+        self.d = d;
+    }
+
+    public isolated function test2(boolean? e) {
+        if (e is ()) {
+            return;
+        }
+        self.d = e;
+    }
+
+    public isolated function test3(boolean e) {
+        if (self.f is int) {
+            return;
+        }
+        self.d = e;
+    }
+}
+
+class A4 {
+    private string c = "";
+    private string d = "";
+
+    function init() {
+        self.test(self.d);
+    }
+
+    function test(string s) {
+        self.c = s;
+    }
+}
+
+service class SA {
+    private string b = ""; // warning
+    private string c = "";
+    private string d = "";
+
+    function init() {
+        self.test(self.d);
+    }
+
+    isolated function test(string s) {
+        self.c = s;
+    }
+}

scan-command/src/test/resources/testng.xml

@@ -31,12 +31,13 @@ under the License.
             <class name="io.ballerina.scan.internal.CoreRuleTest"/>
             <class name="io.ballerina.scan.internal.Rule001Test"/>
             <class name="io.ballerina.scan.internal.Rule002Test"/>
+            <class name="io.ballerina.scan.internal.Rule003And004Test"/>
+            <class name="io.ballerina.scan.internal.Rule005And006Test"/>
             <class name="io.ballerina.scan.internal.Rule007Test"/>
             <class name="io.ballerina.scan.internal.Rule008Test"/>
             <class name="io.ballerina.scan.internal.Rule009Test"/>
             <class name="io.ballerina.scan.internal.Rule010Test"/>
-            <class name="io.ballerina.scan.internal.Rule003And004Test"/>
-            <class name="io.ballerina.scan.internal.Rule005And006Test"/>
+            <class name="io.ballerina.scan.internal.Rule011Test"/>
             <class name="io.ballerina.scan.internal.ProjectAnalyzerTest"/>
             <class name="io.ballerina.scan.utils.ScanUtilsTest"/>
             <class name="io.ballerina.scan.utils.DiagnosticLogTest"/>