feat: add inner_class_may_be_static rule (#239)

code-transformation/src/main/java/xyz/keksdose/spoon/code_solver/analyzer/qodana/QodanaRules.java

@@ -4,6 +4,7 @@
 import java.util.function.Function;
 import xyz.keksdose.spoon.code_solver.analyzer.AnalyzerRule;
 import xyz.keksdose.spoon.code_solver.analyzer.qodana.rules.AbstractRefactoring;
+import xyz.keksdose.spoon.code_solver.analyzer.qodana.rules.InnerClassMayBeStatic;
 import xyz.keksdose.spoon.code_solver.analyzer.qodana.rules.MethodMayBeStatic;
 import xyz.keksdose.spoon.code_solver.analyzer.qodana.rules.NonProtectedConstructorInAbstractClass;
 import xyz.keksdose.spoon.code_solver.analyzer.qodana.rules.NonStrictComparisonCanBeEquality;
@@ -35,7 +36,8 @@ public enum QodanaRules implements AnalyzerRule {
     UNUSED_IMPORT("UnusedImport", UnusedImport::new),
     PROTECTED_MEMBER_IN_FINAL_CLASS("ProtectedMemberInFinalClass", ProtectedMemberInFinalClass::new),
     UNNECESSARY_MODIFIER("UnnecessaryModifier", UnnecessaryModifier::new),
-    POINTLESS_BOOLEAN_EXPRESSION("PointlessBooleanExpression", PointlessBooleanExpression::new);
+    POINTLESS_BOOLEAN_EXPRESSION("PointlessBooleanExpression", PointlessBooleanExpression::new),
+    INNER_CLASS_MAY_BE_STATIC("InnerClassMayBeStatic", InnerClassMayBeStatic::new);
 
     private final String ruleId;
     private final Function<AnalyzerResult, AbstractRefactoring> refactoring;

code-transformation/src/main/java/xyz/keksdose/spoon/code_solver/analyzer/qodana/rules/InnerClassMayBeStatic.java

@@ -0,0 +1,77 @@
+package xyz.keksdose.spoon.code_solver.analyzer.qodana.rules;
+
+import java.nio.file.Path;
+import java.util.HashSet;
+import java.util.List;
+import spoon.reflect.declaration.CtElement;
+import spoon.reflect.declaration.CtType;
+import spoon.reflect.declaration.ModifierKind;
+import xyz.keksdose.spoon.code_solver.analyzer.PositionScanner;
+import xyz.keksdose.spoon.code_solver.api.analyzer.AnalyzerResult;
+import xyz.keksdose.spoon.code_solver.history.Change;
+import xyz.keksdose.spoon.code_solver.history.ChangeListener;
+import xyz.keksdose.spoon.code_solver.history.MarkdownString;
+import xyz.keksdose.spoon.code_solver.transformations.BadSmell;
+
+public class InnerClassMayBeStatic extends AbstractRefactoring {
+
+    private static final BadSmell badSmell = new BadSmell() {
+        @Override
+        public MarkdownString getName() {
+            return MarkdownString.fromMarkdown("InnerClassMayBeStatic");
+        }
+
+        @Override
+        public MarkdownString getDescription() {
+            return MarkdownString.fromMarkdown(
+                    """
+        Inner classes that do not reference their enclosing instances can be made static.
+        This prevents a common cause of memory leaks and uses less memory per instance of the class.
+        """);
+        }
+    };
+
+    public InnerClassMayBeStatic(AnalyzerResult result) {
+        super(result);
+    }
+
+    @Override
+    public void refactor(ChangeListener listener, CtType<?> type) {
+        if (!isSameType(type, Path.of(result.filePath()))) {
+            return;
+        }
+        for (CtType<?> ctType : filterMatches(PositionScanner.findLineOnly(type, result.position()))) {
+            var modifiers = new HashSet<>(ctType.getModifiers());
+            modifiers.add(ModifierKind.STATIC);
+            ctType.setModifiers(modifiers);
+            String format = "Add to inner class %s modifier static";
+            String markdown = String.format(format, "`" + ctType.getSimpleName() + "`");
+            String text = String.format(format, ctType.getQualifiedName());
+            MarkdownString markdownString = MarkdownString.fromMarkdown(text, markdown);
+            Change change = new Change(badSmell, markdownString, getMostOuterType(type), result);
+            listener.setChanged(getMostOuterType(type), change);
+        }
+    }
+
+    private Iterable<? extends CtType<?>> filterMatches(List<CtElement> findLineOnly) {
+        return findLineOnly.stream()
+                .filter(v -> v instanceof CtType<?>)
+                .map(v -> (CtType<?>) v)
+                .filter(v -> !v.isTopLevel())
+                .filter(v -> !v.getModifiers().contains(ModifierKind.STATIC))
+                .toList();
+    }
+
+    @Override
+    public List<BadSmell> getHandledBadSmells() {
+        return List.of(badSmell);
+    }
+
+    private CtType<?> getMostOuterType(CtType<?> inner) {
+        if (inner.getDeclaringType() == null) {
+            return inner;
+        } else {
+            return getMostOuterType(inner.getDeclaringType());
+        }
+    }
+}

code-transformation/src/main/java/xyz/keksdose/spoon/code_solver/history/Change.java

@@ -17,14 +17,14 @@ public class Change {
     public Change(String text, String issue, CtType<?> affectedType) {
         this.text = MarkdownString.fromRaw(text);
         this.issue = issue;
-        this.affectedType = affectedType;
+        this.affectedType = getMostOuterType(affectedType);
     }
 
     public Change(BadSmell badSmell, MarkdownString text, CtType<?> affectedType) {
         this.text = text;
         this.issue = badSmell.getName().asText();
         this.badsmell = badSmell;
-        this.affectedType = affectedType;
+        this.affectedType = getMostOuterType(affectedType);
     }
 
     public Change(BadSmell badSmell, MarkdownString text, CtType<?> affectedType, AnalyzerResult analyzerResult) {
@@ -85,4 +85,12 @@ public boolean equals(Object obj) {
     public @Nullable AnalyzerResult getAnalyzerResult() {
         return analyzerResult;
     }
+
+    private CtType<?> getMostOuterType(CtType<?> inner) {
+        if (inner.getDeclaringType() == null) {
+            return inner;
+        } else {
+            return getMostOuterType(inner.getDeclaringType());
+        }
+    }
 }

code-transformation/src/test/java/xyz/keksdose/spoon/code_solver/transformations/qodana/InnerClassMayBeStaticTest.java

@@ -0,0 +1,23 @@
+package xyz.keksdose.spoon.code_solver.transformations.qodana;
+
+import java.io.File;
+import java.io.IOException;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import xyz.keksdose.spoon.code_solver.analyzer.qodana.rules.InnerClassMayBeStatic;
+import xyz.keksdose.spoon.code_solver.api.analyzer.AnalyzerResult;
+import xyz.keksdose.spoon.code_solver.api.analyzer.Position;
+import xyz.keksdose.spoon.code_solver.transformations.TestAnalyzerResult;
+import xyz.keksdose.spoon.code_solver.transformations.TransformationTestUtils;
+
+public class InnerClassMayBeStaticTest {
+
+    @Test
+    void landLordInnerClassMabyBeStatic(@TempDir File dir) throws IOException {
+        Position position = new Position(296, 0, 0, 0, 0, 80);
+        AnalyzerResult result = new TestAnalyzerResult("Landlordbase.java", position);
+        String resourcePath = "projects/refactorings/InnerClassMayBeStatic/Landlordbase.java";
+        var copy = TransformationTestUtils.transform(new InnerClassMayBeStatic(result), resourcePath, dir);
+        TransformationTestUtils.compareContent(copy, resourcePath);
+    }
+}