Add Early Return Violations

README.md

@@ -71,7 +71,8 @@ github.feedback=true
 # Style category configuration.
 # Valid <category>: Formatting, ClassNames, MethodNames, VariableNames,
 #                   PackageNames, Commenting, JavaDoc, PrivateMembers,
-#                   Ordering, Useless, StringConcatenation, Clones, JavaFX.
+#                   Ordering, Useless, StringConcatenation, Clones, JavaFX,
+#                   EarlyReturn.
 
 # If scoring for <category> is enabled.
 # Required: No, Default: false.

src/main/java/gradestyle/validator/Category.java

@@ -12,6 +12,7 @@
 import com.github.javaparser.ast.body.Parameter;
 import com.github.javaparser.ast.body.VariableDeclarator;
 import com.github.javaparser.ast.comments.Comment;
+import com.github.javaparser.ast.stmt.IfStmt;
 import gradestyle.Repo;
 import gradestyle.config.CategoryConfig;
 import gradestyle.util.FileUtils;
@@ -39,7 +40,8 @@ public enum Category {
   Useless,
   StringConcatenation,
   Clones,
-  JavaFX;
+  JavaFX,
+  EarlyReturn;
 
   public static Map<Category, Integer> getCategoryScores(
       ValidationResult result, List<CategoryConfig> configs) throws IOException {
@@ -150,6 +152,9 @@ private long getNormalisation(Repo repo) throws IOException {
                   .mapToInt(Range::getLineCount)
                   .sum();
           break;
+        case EarlyReturn:
+          normalisation += ifStatementCounter(cu);
+          break;
         default:
           throw new IllegalArgumentException("Unknown category: " + this);
       }
@@ -187,6 +192,10 @@ private int constructorCounter(CompilationUnit cu) {
     return cu.findAll(ConstructorDeclaration.class).size();
   }
 
+  private int ifStatementCounter(CompilationUnit cu) {
+    return cu.findAll(IfStmt.class).size();
+  }
+
   public List<Type> getTypes() {
     return Arrays.stream(Type.values()).filter(type -> type.getCategory() == this).toList();
   }

src/main/java/gradestyle/validator/Type.java

@@ -95,7 +95,9 @@ public enum Type {
   JavaFX_Initializer,
   JavaFX_EventHandlerName,
   JavaFX_EventHandlerAnnotation,
-  JavaFX_EventHandlerPrivate;
+  JavaFX_EventHandlerPrivate,
+
+  EarlyReturn;
 
   public Category getCategory() {
     return Category.valueOf(name().split("_")[0]);
@@ -280,6 +282,9 @@ public String getMessage() {
       case JavaFX_EventHandlerPrivate:
         return "This event handler should have a different access modifier.";
 
+      case EarlyReturn:
+        return "This conditional could have been an early return.";
+
       default:
         throw new IllegalArgumentException("Unknown type: " + this);
     }

src/main/java/gradestyle/validator/pmd/EarlyReturn.java

@@ -0,0 +1,38 @@
+package gradestyle.validator.pmd;
+
+import net.sourceforge.pmd.lang.java.ast.ASTBlock;
+import net.sourceforge.pmd.lang.java.ast.ASTBlockStatement;
+import net.sourceforge.pmd.lang.java.ast.ASTIfStatement;
+import net.sourceforge.pmd.lang.java.ast.ASTMethodDeclaration;
+import net.sourceforge.pmd.lang.java.ast.ASTStatement;
+import net.sourceforge.pmd.lang.java.ast.JavaNode;
+import net.sourceforge.pmd.lang.java.rule.AbstractJavaRule;
+
+public class EarlyReturn extends AbstractJavaRule {
+  public EarlyReturn() {
+    addRuleChainVisit(ASTMethodDeclaration.class);
+  }
+
+  @Override
+  public Object visit(ASTMethodDeclaration method, Object data) {
+    ASTBlock body = method.getBody();
+
+    if (body == null || body.getNumChildren() == 0) {
+      return data;
+    }
+
+    JavaNode blockNode = body.getChild(body.getNumChildren() - 1);
+
+    if (blockNode instanceof ASTBlockStatement blockStmt) {
+      JavaNode stmtNode = blockStmt.getChild(0);
+
+      if (stmtNode instanceof ASTStatement stmt) {
+        if (stmt.getChild(0) instanceof ASTIfStatement conditional) {
+          asCtx(data).addViolation(conditional);
+        }
+      }
+    }
+
+    return data;
+  }
+}

src/main/java/gradestyle/validator/pmd/Pmd.java

@@ -97,6 +97,8 @@ private Type getType(Rule rule) {
         return Type.VariableNames_FinalStaticUppercase;
       case "StringConcatenation":
         return Type.StringConcatenation;
+      case "EarlyReturn":
+        return Type.EarlyReturn;
       default:
         throw new IllegalArgumentException("Unknown rule: " + rule.getName());
     }

src/main/java/gradestyle/validator/pmd/pmd.xml

@@ -35,4 +35,5 @@
   </rule>
 
   <rule name="StringConcatenation" language="java" class="gradestyle.validator.pmd.StringConcatenation"/>
+  <rule name="EarlyReturn" language="java" class="gradestyle.validator.pmd.EarlyReturn"/>
 </ruleset>