Escape empty strings when printing symbols

Otherwise they are not re-readable!

Fixes #484.

Core/SoarKernel/src/soar_representation/symbol.cpp

@@ -90,7 +90,7 @@ bool make_string_rereadable(std::string &pStr)
 
     // bool has_angle_bracket = pCStr[0] == '<' || pCStr[pLength - 1] == '>';
 
-    if ((!possible_sc)   || possible_var || possible_ic || possible_fc || possible_id || (!is_rereadable))
+    if ((!possible_sc) || possible_var || possible_ic || possible_fc || possible_id || (!is_rereadable) || (!pLength) )
     {
         /* BUGBUG - if in context where id's could occur, should check possible_id flag here also */
         pStr = string_to_escaped_string(pCStr, '|');

UnitTests/SoarUnitTests/MiscTests.cpp

@@ -369,6 +369,24 @@ void MiscTests::testStopPhaseRetrieval()
 	assertTrue(response.GetArgInt(sml::sml_Names::kParamPhase, -1) == sml::smlPhase::sml_APPLY_PHASE);
 }
 
+
+
+void MiscTests::testProductionPrinting()
+{
+    // Tries to fully exercise Symbol::to_string
+    agent->ExecuteCommandLine("sp {foo (state <s> ^superstate nil) --> (<s> ^one 1 ^two 2.0 ^three 3.0e0 ^foo bar ^|| hi ^|<bar>| bar ^|^baz| baz ^1 one ^|2.0| two)}");
+    no_agent_assertTrue(agent->GetLastCommandLineResult());
+    std::string spMessage = agent->ExecuteCommandLine("print foo");
+//     sp {foo
+//     (state <s> ^superstate nil)
+//     -->
+//     (<s> ^one 1 ^two 2.000000 ^three 3.000000 ^foo bar ^|| hi ^|<bar>| bar
+//            ^|^baz| baz ^1 one ^|2.0| two)
+// }
+//
+    no_agent_assertTrue(spMessage == "sp {foo\n    (state <s> ^superstate nil)\n    -->\n    (<s> ^one 1 ^two 2.000000 ^three 3.000000 ^foo bar ^|| hi ^|<bar>| bar\n           ^|^baz| baz ^1 one ^|2.0| two)\n}\n\n");
+}
+
 //void MiscTests::testSoarDebugger()
 //{
 //	bool result = agent->SpawnDebugger();

UnitTests/SoarUnitTests/MiscTests.hpp

@@ -63,6 +63,9 @@ class MiscTests : public FunctionalTestHarness
 	void testNegated_Operator_Crash();
 	void testOp_Augmentation_Crash();
 
+	TEST(testProductionPrinting, -1)
+    void testProductionPrinting();
+
 	// If you would like to test the Soar Debugger Spawning, uncomment below.
 	// It may or may not work but should unless you're running without a GUI.
 //	TEST(testSoarDebugger, -1)