Fixed issue 2945 (#2946)

* Fixed #2945

* Added unit tests for #2945

* Dissalow iterator on empty Var (#2945)

* Updated unit tests for #2945

* More concise unit tests for #2945

* Removed some more clutter (#2945)

Foundation/include/Poco/Dynamic/Var.h

@@ -737,7 +737,7 @@ inline const std::type_info& Var::type() const
 
 inline Var::ConstIterator Var::begin() const
 {
-	if (isEmpty()) return ConstIterator(const_cast<Var*>(this), true);
+	if (size() == 0) return ConstIterator(const_cast<Var*>(this), true);
 
 	return ConstIterator(const_cast<Var*>(this), false);
 }
@@ -749,7 +749,7 @@ inline Var::ConstIterator Var::end() const
 
 inline Var::Iterator Var::begin()
 {
-	if (isEmpty()) return Iterator(const_cast<Var*>(this), true);
+	if (size() == 0) return Iterator(const_cast<Var*>(this), true);
 
 	return Iterator(const_cast<Var*>(this), false);
 }

Foundation/src/VarIterator.cpp

@@ -31,6 +31,7 @@ VarIterator::VarIterator(Var* pVar, bool positionEnd):
 	_pVar(pVar),
 	_position(positionEnd ? POSITION_END : 0)
 {
+    if (!_pVar || _pVar->isEmpty()) throw InvalidAccessException("Cannot create iterator on empty Var");
 }
 
 

Foundation/testsuite/src/VarTest.cpp

@@ -2973,8 +2973,15 @@ void VarTest::testEmpty()
 void VarTest::testIterator()
 {
 	Var da;
-	assertTrue (da.isEmpty());
-	assertTrue (da.begin() == da.end());
+	try
+	{
+		auto it = da.begin();
+		fail("calling begin() on empty Var must throw");
+	}
+	catch (const InvalidAccessException&) { }
+
+	da = Poco::Dynamic::Array();
+	assertTrue(da.begin() == da.end());
 
 	da = 1;
 	assertTrue (!da.isEmpty());

Foundation/testsuite/src/VarTest.h

@@ -184,14 +184,29 @@ class VarTest: public CppUnit::TestCase
 	void testContainerIterator()
 	{
 		C cont;
+		Poco::Dynamic::Var arr(cont);
+		int counter = 0;
+
+		// test empty
+		assertTrue (arr.size() == 0);
+		Poco::Dynamic::Var::Iterator it = arr.begin();
+		Poco::Dynamic::Var::Iterator end = arr.end();
+
+		for (; it != end; ++it)
+		{
+			*it = ++counter;
+		}
+		assertTrue(counter == 0);
+
+		// test non-empty
 		cont.push_back(1);
 		cont.push_back("2");
 		cont.push_back(3.5);
-		Poco::Dynamic::Var arr(cont);
+		arr = cont;
 		assertTrue (arr.size() == 3);
-		Poco::Dynamic::Var::Iterator it = arr.begin();
-		Poco::Dynamic::Var::Iterator end = arr.end();
-		int counter = 0;
+		it = arr.begin();
+		end = arr.end();
+		counter = 0;
 		for (; it != end; ++it)
 		{
 			switch (++counter)