Iterator conversions

include/json/value.h

@@ -738,6 +738,7 @@ class JSON_API ValueConstIterator : public ValueIteratorBase {
   typedef ValueConstIterator SelfType;
 
   ValueConstIterator();
+  ValueConstIterator(ValueIterator const& other);
 
 private:
 /*! \internal Use by Value to create an iterator.
@@ -787,7 +788,7 @@ class JSON_API ValueIterator : public ValueIteratorBase {
   typedef ValueIterator SelfType;
 
   ValueIterator();
-  ValueIterator(const ValueConstIterator& other);
+  explicit ValueIterator(const ValueConstIterator& other);
   ValueIterator(const ValueIterator& other);
 
 private:

src/lib_json/json_valueiterator.inl

@@ -129,6 +129,9 @@ ValueConstIterator::ValueConstIterator(
     const Value::ObjectValues::iterator& current)
     : ValueIteratorBase(current) {}
 
+ValueConstIterator::ValueConstIterator(ValueIterator const& other)
+    : ValueIteratorBase(other) {}
+
 ValueConstIterator& ValueConstIterator::
 operator=(const ValueIteratorBase& other) {
   copy(other);
@@ -149,7 +152,9 @@ ValueIterator::ValueIterator(const Value::ObjectValues::iterator& current)
     : ValueIteratorBase(current) {}
 
 ValueIterator::ValueIterator(const ValueConstIterator& other)
-    : ValueIteratorBase(other) {}
+    : ValueIteratorBase(other) {
+  throwRuntimeError("ConstIterator to Iterator should never be allowed.");
+}
 
 ValueIterator::ValueIterator(const ValueIterator& other)
     : ValueIteratorBase(other) {}

src/test_lib_json/main.cpp

@@ -8,6 +8,9 @@
 #include <json/json.h>
 #include <cstring>
 #include <limits>
+#include <sstream>
+#include <string>
+#include <iomanip>
 
 // Make numeric limits more convenient to talk about.
 // Assumes int type in 32 bits.
@@ -2430,6 +2433,33 @@ JSONTEST_FIXTURE(IteratorTest, indexes) {
   JSONTEST_ASSERT(it == json.end());
 }
 
+JSONTEST_FIXTURE(IteratorTest, const) {
+  Json::Value const v;
+  JSONTEST_ASSERT_THROWS(
+    Json::Value::iterator it(v.begin()) // Compile, but throw.
+  );
+
+  Json::Value value;
+
+  for(int i = 9; i < 12; ++i)
+  {
+    std::ostringstream out;
+    out << std::setw(2) << i;
+    std::string str = out.str();
+    value[str] = str;
+  }
+
+  std::ostringstream out;
+  //in old code, this will get a compile error
+  Json::Value::const_iterator iter = value.begin();
+  for(; iter != value.end(); ++iter)
+  {
+    out << *iter << ',';
+  }
+  std::string expected = "\" 9\",\"10\",\"11\",";
+  JSONTEST_ASSERT_STRING_EQUAL(expected, out.str());
+}
+
 int main(int argc, const char* argv[]) {
   JsonTest::Runner runner;
   JSONTEST_REGISTER_FIXTURE(runner, ValueTest, checkNormalizeFloatingPointStr);
@@ -2500,6 +2530,7 @@ int main(int argc, const char* argv[]) {
   JSONTEST_REGISTER_FIXTURE(runner, IteratorTest, distance);
   JSONTEST_REGISTER_FIXTURE(runner, IteratorTest, names);
   JSONTEST_REGISTER_FIXTURE(runner, IteratorTest, indexes);
+  JSONTEST_REGISTER_FIXTURE(runner, IteratorTest, const);
 
   return runner.runCommandLine(argc, argv);
 }