Make validator library and put the first validation in it.

javaparser-core/src/main/java/com/github/javaparser/JavaParser.java

@@ -35,6 +35,10 @@
 import com.github.javaparser.ast.stmt.ExplicitConstructorInvocationStmt;
 import com.github.javaparser.ast.stmt.Statement;
 import com.github.javaparser.ast.type.ClassOrInterfaceType;
+import com.github.javaparser.ast.validator.DefaultValidator;
+import com.github.javaparser.ast.validator.NoProblemsValidator;
+import com.github.javaparser.ast.validator.ProblemReporter;
+import com.github.javaparser.ast.validator.Validator;
 import com.github.javaparser.javadoc.Javadoc;
 
 import java.io.*;
@@ -86,6 +90,13 @@ private GeneratedJavaParser getParserForProvider(Provider provider) {
         return astParser;
     }
 
+    /**
+     * @deprecated use the other parse method.
+     */
+    public <N extends Node> ParseResult<N> parse(ParseStart<N> start, Provider provider) {
+        return parse(start, provider, new DefaultValidator());
+    }
+
     /**
      * Parses source code.
      * It takes the source code from a Provider.
@@ -96,7 +107,7 @@ private GeneratedJavaParser getParserForProvider(Provider provider) {
      * @param <N> the subclass of Node that is the result of parsing in the start.
      * @return the parse result, a collection of encountered problems, and some extra data.
      */
-    public <N extends Node> ParseResult<N> parse(ParseStart<N> start, Provider provider) {
+    public <N extends Node> ParseResult<N> parse(ParseStart<N> start, Provider provider, Validator validator) {
         assertNotNull(start);
         assertNotNull(provider);
         final GeneratedJavaParser parser = getParserForProvider(provider);
@@ -106,6 +117,8 @@ public <N extends Node> ParseResult<N> parse(ParseStart<N> start, Provider provi
                 final CommentsCollection comments = parser.getCommentsCollection();
                 commentsInserter.insertComments(resultNode, comments.copy().getComments());
             }
+
+            validator.validate(resultNode, new ProblemReporter(parser.problems));
 
             return new ParseResult<>(resultNode, parser.problems, parser.getTokens(),
                     parser.getCommentsCollection());
@@ -361,8 +374,11 @@ public static Statement parseStatement(final String statement) {
     }
 
     private static <T extends Node> T simplifiedParse(ParseStart<T> context, Provider provider) {
-        ParseResult<T> result = new JavaParser(new ParserConfiguration()).parse(context, provider);
-        return result.getResult().orElseThrow(() -> new ParseProblemException(result.getProblems()));
+        ParseResult<T> result = new JavaParser(new ParserConfiguration()).parse(context, provider, new DefaultValidator());
+        if (result.isSuccessful()) {
+            return result.getResult().get();
+        }
+        throw new ParseProblemException(result.getProblems());
     }
 
     /**

javaparser-core/src/main/java/com/github/javaparser/ast/expr/MarkerAnnotationExpr.java

@@ -29,7 +29,6 @@
 import com.github.javaparser.metamodel.MarkerAnnotationExprMetaModel;
 import com.github.javaparser.metamodel.JavaParserMetaModel;
 import static com.github.javaparser.JavaParser.parseName;
-
 import static com.github.javaparser.JavaParser.parseName;
 
 /**

javaparser-core/src/main/java/com/github/javaparser/ast/validator/DefaultValidator.java

@@ -0,0 +1,21 @@
+package com.github.javaparser.ast.validator;
+
+import com.github.javaparser.ast.stmt.TryStmt;
+
+/**
+ * The validator that is used by default by the static JavaParser methods.
+ */
+public class DefaultValidator extends Validators {
+    public DefaultValidator() {
+        super(new VisitorValidator() {
+            @Override
+            public void visit(TryStmt n, ProblemReporter reporter) {
+                if (n.getCatchClauses().isEmpty()
+                        && n.getResources().isEmpty()
+                        && !n.getFinallyBlock().isPresent()) {
+                    reporter.report("Try has no finally, no catch, and no resources", n);
+                }
+            }
+        });
+    }
+}

javaparser-core/src/main/java/com/github/javaparser/ast/validator/NoProblemsValidator.java

@@ -0,0 +1,12 @@
+package com.github.javaparser.ast.validator;
+
+import com.github.javaparser.ast.Node;
+
+/**
+ * Stub validator for when no validation is wanted.
+ */
+public class NoProblemsValidator implements Validator {
+    @Override
+    public void validate(Node node, ProblemReporter problemReporter) {
+    }
+}

javaparser-core/src/main/java/com/github/javaparser/ast/validator/ProblemReporter.java

@@ -0,0 +1,32 @@
+package com.github.javaparser.ast.validator;
+
+import com.github.javaparser.Problem;
+import com.github.javaparser.Range;
+import com.github.javaparser.ast.Node;
+
+import java.util.List;
+
+/**
+ * A simple interface where validators can report found problems.
+ */
+public class ProblemReporter {
+    private final List<Problem> problems;
+
+    public ProblemReporter(List<Problem> problems) {
+        this.problems = problems;
+    }
+
+    /**
+     * Report a problem.
+     *
+     * @param message description of the problem
+     * @param node the node in which the problem occurred, used to find the Range of the problem.
+     */
+    public void report(String message, Node node) {
+        report(message, node.getRange().orElse(null));
+    }
+
+    public void report(String message, Range range) {
+        problems.add(new Problem(message, range, null));
+    }
+}

javaparser-core/src/main/java/com/github/javaparser/ast/validator/Validator.java

@@ -0,0 +1,15 @@
+package com.github.javaparser.ast.validator;
+
+import com.github.javaparser.ast.Node;
+
+/**
+ * A validator that can be run on a node to check for semantic errors.
+ * It is fully up to the implementor how to do this.
+ */
+public interface Validator {
+    /**
+     * @param node the node that wants to be validated
+     * @param problemReporter when found, validation errors can be reported here
+     */
+    void validate(Node node, ProblemReporter problemReporter);
+}

javaparser-core/src/main/java/com/github/javaparser/ast/validator/Validators.java

@@ -0,0 +1,27 @@
+package com.github.javaparser.ast.validator;
+
+import com.github.javaparser.ast.Node;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * A validator that will call a collection of validators.
+ */
+public class Validators implements Validator {
+    private final List<Validator> validators = new ArrayList<>();
+
+    public Validators(Validator... validators) {
+        this.validators.addAll(Arrays.asList(validators));
+    }
+
+    public List<Validator> getValidators() {
+        return validators;
+    }
+
+    @Override
+    public void validate(Node node, ProblemReporter problemReporter) {
+        validators.forEach(v -> v.validate(node, problemReporter));
+    }
+}

javaparser-core/src/main/java/com/github/javaparser/ast/validator/VisitorValidator.java

@@ -0,0 +1,16 @@
+package com.github.javaparser.ast.validator;
+
+import com.github.javaparser.ast.Node;
+import com.github.javaparser.ast.visitor.VoidVisitorAdapter;
+
+/**
+ * A validator that uses a visitor for validation.
+ * This class is the visitor too.
+ * Implement the "visit" methods you want to use for validation.
+ */
+public abstract class VisitorValidator extends VoidVisitorAdapter<ProblemReporter> implements Validator {
+    @Override
+    public void validate(Node node, ProblemReporter problemReporter) {
+        node.accept(this, problemReporter);
+    }
+}

javaparser-core/src/main/java/com/github/javaparser/metamodel/JavaParserMetaModel.java

@@ -563,10 +563,10 @@ private static void initializePropertyMetaModels() {
         unaryExprMetaModel.getDeclaredPropertyMetaModels().add(unaryExprMetaModel.expressionPropertyMetaModel);
         unaryExprMetaModel.operatorPropertyMetaModel = new PropertyMetaModel(unaryExprMetaModel, "operator", com.github.javaparser.ast.expr.UnaryExpr.Operator.class, Optional.empty(), false, false, false, false, false);
         unaryExprMetaModel.getDeclaredPropertyMetaModels().add(unaryExprMetaModel.operatorPropertyMetaModel);
-        unaryExprMetaModel.postfixPropertyMetaModel = new PropertyMetaModel(unaryExprMetaModel, "postfix", boolean.class, Optional.empty(), false, true, false, false, false);
-        unaryExprMetaModel.getDerivedPropertyMetaModels().add(unaryExprMetaModel.postfixPropertyMetaModel);
         unaryExprMetaModel.prefixPropertyMetaModel = new PropertyMetaModel(unaryExprMetaModel, "prefix", boolean.class, Optional.empty(), false, true, false, false, false);
         unaryExprMetaModel.getDerivedPropertyMetaModels().add(unaryExprMetaModel.prefixPropertyMetaModel);
+        unaryExprMetaModel.postfixPropertyMetaModel = new PropertyMetaModel(unaryExprMetaModel, "postfix", boolean.class, Optional.empty(), false, true, false, false, false);
+        unaryExprMetaModel.getDerivedPropertyMetaModels().add(unaryExprMetaModel.postfixPropertyMetaModel);
         variableDeclarationExprMetaModel.annotationsPropertyMetaModel = new PropertyMetaModel(variableDeclarationExprMetaModel, "annotations", com.github.javaparser.ast.expr.AnnotationExpr.class, Optional.of(annotationExprMetaModel), false, false, true, false, false);
         variableDeclarationExprMetaModel.getDeclaredPropertyMetaModels().add(variableDeclarationExprMetaModel.annotationsPropertyMetaModel);
         variableDeclarationExprMetaModel.modifiersPropertyMetaModel = new PropertyMetaModel(variableDeclarationExprMetaModel, "modifiers", com.github.javaparser.ast.Modifier.class, Optional.empty(), false, false, false, true, false);

javaparser-core/src/main/java/com/github/javaparser/metamodel/UnaryExprMetaModel.java

@@ -12,8 +12,8 @@ public class UnaryExprMetaModel extends ExpressionMetaModel {
 
     public PropertyMetaModel operatorPropertyMetaModel;
 
-    public PropertyMetaModel postfixPropertyMetaModel;
-
     public PropertyMetaModel prefixPropertyMetaModel;
+
+    public PropertyMetaModel postfixPropertyMetaModel;
 }
 

javaparser-core/src/main/javacc/java.jj

@@ -3193,12 +3193,7 @@ TryStmt TryStatement():
   	|
   		"finally" finallyBlock = Block()
   )
-  {
-    if (finallyBlock == null && catchs.isEmpty() && resources.isEmpty()) {
-      addProblem("Try has no finally, no catch, and no resources");
-    }
-    return new TryStmt(range(begin, tokenEnd()), resources, tryBlock, catchs, finallyBlock);
-  }
+  { return new TryStmt(range(begin, tokenEnd()), resources, tryBlock, catchs, finallyBlock); }
 }
 
 

javaparser-testing/src/test/java/com/github/javaparser/ast/validator/DefaultValidatorTest.java

@@ -0,0 +1,24 @@
+package com.github.javaparser.ast.validator;
+
+import com.github.javaparser.JavaParser;
+import com.github.javaparser.ParseResult;
+import com.github.javaparser.ParseStart;
+import com.github.javaparser.ast.stmt.Statement;
+import org.junit.Test;
+
+import static com.github.javaparser.Providers.provider;
+import static org.junit.Assert.assertEquals;
+
+public class DefaultValidatorTest {
+    @Test
+    public void tryWithoutAnything() {
+        ParseResult<Statement> result = new JavaParser().parse(ParseStart.STATEMENT, provider("try{}"), new DefaultValidator());
+        assertEquals("[(line 1,col 1) Try has no finally, no catch, and no resources]", result.getProblems().toString());
+    }
+    @Test
+    public void classExtendingMoreThanOne() {
+        ParseResult<Statement> result = new JavaParser().parse(ParseStart.STATEMENT, provider("try{}"), new DefaultValidator());
+        assertEquals("[(line 1,col 1) Try has no finally, no catch, and no resources]", result.getProblems().toString());
+    }
+
+}

javaparser-testing/src/test/java/com/github/javaparser/ast/validator/ValidatorTest.java

@@ -0,0 +1,19 @@
+package com.github.javaparser.ast.validator;
+
+import com.github.javaparser.JavaParser;
+import com.github.javaparser.ParseResult;
+import com.github.javaparser.ast.CompilationUnit;
+import org.junit.Test;
+
+import static com.github.javaparser.ParseStart.COMPILATION_UNIT;
+import static com.github.javaparser.Providers.provider;
+import static org.junit.Assert.assertEquals;
+
+public class ValidatorTest {
+    @Test
+    public void noProblemsHere() {
+        ParseResult<CompilationUnit> result = new JavaParser().parse(COMPILATION_UNIT, provider("class X{}"), new NoProblemsValidator());
+        assertEquals(true, result.isSuccessful());
+    }
+
+}