Cleanup some Json::Value methods:

* Rename isArray to isArrayOrNull
* Rename isObject to isObjectOrNull
* Introduce isArray and isObject
* Change as many uses of isArrayorNull to isArray as possible
* Change as many uses of isObjectorNull to isObject as possible
* Reject null JSON arrays for subscribe and unsubscribe

src/ripple/app/main/Application.cpp

@@ -1584,7 +1584,7 @@ ApplicationImp::loadLedgerFromFile (
             ledger = ledger.get()["accountState"];
         }
 
-        if (!ledger.get().isArray ())
+        if (!ledger.get().isArrayOrNull ())
         {
             JLOG(m_journal.fatal())
                << "State nodes must be an array";
@@ -1599,7 +1599,7 @@ ApplicationImp::loadLedgerFromFile (
         {
             Json::Value& entry = ledger.get()[index];
 
-            if (!entry.isObject())
+            if (!entry.isObjectOrNull())
             {
                 JLOG(m_journal.fatal())
                     << "Invalid entry in ledger";

src/ripple/app/misc/impl/AccountTxPaging.cpp

@@ -79,7 +79,7 @@ accountTxPage (
     bool bAdmin,
     std::uint32_t page_length)
 {
-    bool lookingForMarker =  !token.isNull() && token.isObject();
+    bool lookingForMarker = token.isObject();
 
     std::uint32_t numberOfResults;
 

src/ripple/json/impl/Object.cpp

@@ -196,7 +196,7 @@ namespace {
 template <class Object>
 void doCopyFrom (Object& to, Json::Value const& from)
 {
-    assert (from.isObject());
+    assert (from.isObjectOrNull());
     auto members = from.getMemberNames();
     for (auto& m: members)
         to[m] = from[m];

src/ripple/json/impl/json_reader.cpp

@@ -124,7 +124,7 @@ Reader::parse ( const char* beginDoc, const char* endDoc,
     Token token;
     skipCommentTokens ( token );
 
-    if ( !root.isArray ()  &&  !root.isObject () )
+    if ( !root.isNull() && !root.isArray() && !root.isObject() )
     {
         // Set error location to start of doc, ideally should be first token found in doc
         token.type_ = tokenError;

src/ripple/json/impl/json_value.cpp

@@ -779,7 +779,7 @@ Value::operator bool () const
     if (isString ())
     {
         auto s = asCString();
-        return s && strlen(s);
+        return s && s[0];
     }
 
     return ! (isArray() || isObject()) || size ();
@@ -1093,6 +1093,12 @@ Value::isString () const
 
 bool
 Value::isArray() const
+{
+    return type_ == arrayValue;
+}
+
+bool
+Value::isArrayOrNull () const
 {
     return type_ == nullValue  ||  type_ == arrayValue;
 }
@@ -1100,6 +1106,12 @@ Value::isArray () const
 
 bool
 Value::isObject() const
+{
+    return type_ == objectValue;
+}
+
+bool
+Value::isObjectOrNull () const
 {
     return type_ == nullValue  ||  type_ == objectValue;
 }

src/ripple/json/json_value.h

@@ -263,7 +263,9 @@ public:
     bool isNumeric () const;
     bool isString () const;
     bool isArray() const;
+    bool isArrayOrNull () const;
     bool isObject() const;
+    bool isObjectOrNull () const;
 
     bool isConvertibleTo ( ValueType other ) const;
 

src/ripple/net/impl/RPCCall.cpp

@@ -513,7 +513,7 @@ private:
 
         if (reader.parse (jvParams[1u].asString (), jvRequest))
         {
-            if (!jvRequest.isObject ())
+            if (!jvRequest.isObjectOrNull ())
                 return rpcError (rpcINVALID_PARAMS);
 
             jvRequest[jss::method] = jvParams[0u];
@@ -544,7 +544,8 @@ private:
                 jv.isMember(jss::id) && jv.isMember(jss::method))
             {
                 if (jv.isMember(jss::params) &&
-                      !(jv[jss::params].isArray() || jv[jss::params].isObject()))
+                      !(jv[jss::params].isNull() || jv[jss::params].isArray() ||
+                                                    jv[jss::params].isObject()))
                     return false;
                 return true;
             }

src/ripple/protocol/impl/STAmount.cpp

@@ -806,7 +806,11 @@ amountFromJson (SField const& name, Json::Value const& v)
     Json::Value currency;
     Json::Value issuer;
 
-    if (v.isObject ())
+    if (v.isNull())
+    {
+        Throw<std::runtime_error> ("XRP may not be specified with a null Json value");
+    }
+    else if (v.isObject())
     {
         value       = v[jss::value];
         currency    = v[jss::currency];
@@ -846,7 +850,7 @@ amountFromJson (SField const& name, Json::Value const& v)
 
     if (native)
     {
-        if (v.isObject ())
+        if (v.isObjectOrNull ())
             Throw<std::runtime_error> ("XRP may not be specified as an object");
         issue = xrpIssue ();
     }

src/ripple/protocol/impl/STParsedJSON.cpp

@@ -495,7 +495,7 @@ static boost::optional<detail::STVar> parseLeaf (
         break;
 
     case STI_VECTOR256:
-        if (! value.isArray ())
+        if (! value.isArrayOrNull ())
         {
             error = array_expected (json_name, fieldName);
             return ret;
@@ -521,7 +521,7 @@ static boost::optional<detail::STVar> parseLeaf (
         break;
 
     case STI_PATHSET:
-        if (!value.isArray ())
+        if (!value.isArrayOrNull ())
         {
             error = array_expected (json_name, fieldName);
             return ret;
@@ -535,7 +535,7 @@ static boost::optional<detail::STVar> parseLeaf (
             {
                 STPath p;
 
-                if (!value[i].isArray ())
+                if (!value[i].isArrayOrNull ())
                 {
                     std::stringstream ss;
                     ss << fieldName << "[" << i << "]";
@@ -709,7 +709,7 @@ static boost::optional <STObject> parseObject (
     int depth,
     Json::Value& error)
 {
-    if (! json.isObject ())
+    if (! json.isObjectOrNull ())
     {
         error = not_an_object (json_name);
         return boost::none;
@@ -743,7 +743,7 @@ static boost::optional <STObject> parseObject (
         case STI_TRANSACTION:
         case STI_LEDGERENTRY:
         case STI_VALIDATION:
-            if (! value.isObject ())
+            if (! value.isObjectOrNull ())
             {
                 error = not_an_object (json_name, fieldName);
                 return boost::none;
@@ -816,7 +816,7 @@ static boost::optional <detail::STVar> parseArray (
     int depth,
     Json::Value& error)
 {
-    if (! json.isArray ())
+    if (! json.isArrayOrNull ())
     {
         error = not_an_array (json_name);
         return boost::none;
@@ -834,11 +834,12 @@ static boost::optional <detail::STVar> parseArray (
 
         for (Json::UInt i = 0; json.isValidIndex (i); ++i)
         {
-            bool const isObject (json[i].isObject());
+            bool const isObjectOrNull (json[i].isObjectOrNull());
-            bool const singleKey (isObject ? json[i].size() == 1 : true);
+            bool const singleKey (isObjectOrNull ? json[i].size() == 1 : true);
 
-            if (!isObject || !singleKey)
+            if (!isObjectOrNull || !singleKey)
             {
+                // null values are !singleKey
                 error = singleton_expected (json_name, i);
                 return boost::none;
             }

src/ripple/rpc/handlers/BookOffers.cpp

@@ -52,22 +52,21 @@ Json::Value doBookOffers (RPC::Context& context)
     if (!context.params.isMember (jss::taker_gets))
         return RPC::missing_field_error (jss::taker_gets);
 
-    if (!context.params[jss::taker_pays].isObject ())
+    Json::Value const& taker_pays = context.params[jss::taker_pays];
+    Json::Value const& taker_gets = context.params[jss::taker_gets];
+
+    if (!taker_pays.isObjectOrNull ())
         return RPC::object_field_error (jss::taker_pays);
 
-    if (!context.params[jss::taker_gets].isObject ())
+    if (!taker_gets.isObjectOrNull ())
         return RPC::object_field_error (jss::taker_gets);
 
-    Json::Value const& taker_pays (context.params[jss::taker_pays]);
-
     if (!taker_pays.isMember (jss::currency))
         return RPC::missing_field_error ("taker_pays.currency");
 
     if (! taker_pays [jss::currency].isString ())
         return RPC::expected_field_error ("taker_pays.currency", "string");
 
-    Json::Value const& taker_gets = context.params[jss::taker_gets];
-
     if (! taker_gets.isMember (jss::currency))
         return RPC::missing_field_error ("taker_gets.currency");
 

src/ripple/rpc/handlers/GatewayBalances.cpp

@@ -116,7 +116,8 @@ Json::Value doGatewayBalances (RPC::Context& context)
         Json::Value const& hw = params[jss::hotwallet];
         bool valid = true;
 
-        if (hw.isArray())
+        // null is treated as a valid 0-sized array of hotwallet
+        if (hw.isArrayOrNull())
         {
             for (unsigned i = 0; i < hw.size(); ++i)
                 valid &= addHotWallet (hw[i]);

src/ripple/rpc/handlers/LedgerEntry.cpp

@@ -64,7 +64,11 @@ Json::Value doLedgerEntry (RPC::Context& context)
     }
     else if (context.params.isMember (jss::directory))
     {
-        if (!context.params[jss::directory].isObject ())
+        if (context.params[jss::directory].isNull())
+        {
+            jvResult[jss::error]   = "malformedRequest";
+        }
+        else if (!context.params[jss::directory].isObject())
         {
             uNodeIndex.SetHex (context.params[jss::directory].asString ());
         }

src/ripple/rpc/handlers/Subscribe.cpp

@@ -195,8 +195,8 @@ Json::Value doSubscribe (RPC::Context& context)
             if (!j.isObject()
                     || !j.isMember (jss::taker_pays)
                     || !j.isMember (jss::taker_gets)
-                    || !j[jss::taker_pays].isObject ()
+                    || !j[jss::taker_pays].isObjectOrNull ()
-                    || !j[jss::taker_gets].isObject ())
+                    || !j[jss::taker_gets].isObjectOrNull ())
                 return rpcError (rpcINVALID_PARAMS);
 
             Book book;

src/ripple/rpc/handlers/Unsubscribe.cpp

@@ -139,8 +139,8 @@ Json::Value doUnsubscribe (RPC::Context& context)
             if (! jv.isObject() ||
                 ! jv.isMember(jss::taker_pays) ||
                 ! jv.isMember(jss::taker_gets) ||
-                ! jv[jss::taker_pays].isObject() ||
+                ! jv[jss::taker_pays].isObjectOrNull() ||
-                ! jv[jss::taker_gets].isObject())
+                ! jv[jss::taker_gets].isObjectOrNull())
             {
                 return rpcError(rpcINVALID_PARAMS);
             }

src/ripple/rpc/impl/ServerHandlerImp.cpp

@@ -334,7 +334,6 @@ ServerHandlerImp::onWSMessage(
     auto const size = boost::asio::buffer_size(buffers);
     if (size > RPC::Tuning::maxRequestSize ||
         ! Json::Reader{}.parse(jv, buffers) ||
-        ! jv ||
         ! jv.isObject())
     {
         Json::Value jvResult(Json::objectValue);
@@ -603,7 +602,7 @@ ServerHandlerImp::processRequest (Port const& port,
         if (jsonRPC.isMember(jss::params) &&
             jsonRPC[jss::params].isArray() &&
             jsonRPC[jss::params].size() > 0 &&
-            jsonRPC[jss::params][Json::UInt(0)].isObject())
+            jsonRPC[jss::params][Json::UInt(0)].isObjectOrNull())
         {
             role = requestRole(
                 required,
@@ -721,7 +720,7 @@ ServerHandlerImp::processRequest (Port const& port,
             else
             {
                 params = std::move (params[0u]);
-                if (!params.isObject())
+                if (!params.isObjectOrNull())
                 {
                     usage.charge(Resource::feeInvalidRPC);
                     HTTPReply (400, "params unparseable", output, rpcJ);

src/test/app/Regression_test.cpp

@@ -213,8 +213,7 @@ struct Regression_test : public beast::unit_test::suite
         std::vector<boost::asio::const_buffer> buffers;
         buffers.emplace_back(buffer(request, 1024));
         buffers.emplace_back(buffer(request.data() + 1024, request.length() - 1024));
-        BEAST_EXPECT(jrReader.parse(jvRequest, buffers) &&
+        BEAST_EXPECT(jrReader.parse(jvRequest, buffers) && jvRequest.isObject());
-            jvRequest && jvRequest.isObject());
     }
 
     void run() override

src/test/protocol/STObject_test.cpp

@@ -38,9 +38,7 @@ public:
     bool parseJSONString (std::string const& json, Json::Value& to)
     {
         Json::Reader reader;
-        return reader.parse(json, to) &&
+        return reader.parse(json, to) && to.isObject();
-                bool (to) &&
-                to.isObject();
     }
 
     void testParseJSONArrayWithInvalidChildrenObjects ()

src/test/rpc/Subscribe_test.cpp

@@ -462,11 +462,16 @@ public:
             BEAST_EXPECT(jr[jss::error_message] == "You don't have permission for this command.");
         }
 
+        std::initializer_list<Json::Value> const nonArrays {Json::nullValue,
+            Json::intValue, Json::uintValue, Json::realValue, "",
+            Json::booleanValue, Json::objectValue};
+
         for (auto const& f : {jss::accounts_proposed, jss::accounts})
         {
+            for (auto const& nonArray : nonArrays)
             {
                 Json::Value jv;
-                jv[f] = "";
+                jv[f] = nonArray;
                 auto jr = wsc->invoke(method, jv) [jss::result];
                 BEAST_EXPECT(jr[jss::error] == "invalidParams");
                 BEAST_EXPECT(jr[jss::error_message] == "Invalid parameters.");
@@ -481,9 +486,10 @@ public:
             }
         }
 
+        for (auto const& nonArray : nonArrays)
         {
             Json::Value jv;
-            jv[jss::books] = "";
+            jv[jss::books] = nonArray;
             auto jr = wsc->invoke(method, jv) [jss::result];
             BEAST_EXPECT(jr[jss::error] == "invalidParams");
             BEAST_EXPECT(jr[jss::error_message] == "Invalid parameters.");
@@ -608,9 +614,10 @@ public:
             BEAST_EXPECT(jr[jss::error_message] == "No such market.");
         }
 
+        for (auto const& nonArray : nonArrays)
         {
             Json::Value jv;
-            jv[jss::streams] = "";
+            jv[jss::streams] = nonArray;
             auto jr = wsc->invoke(method, jv) [jss::result];
             BEAST_EXPECT(jr[jss::error] == "invalidParams");
             BEAST_EXPECT(jr[jss::error_message] == "Invalid parameters.");