ENH: Return error compile-time if required longflag property is not set

TCLAP always requires specification of a "longflag" (even if a shortflag is specified) - see spf13/pflag#139.
If longflag is not set in the module description file for more than one parameter then invalid code is generated (that has longflag set to empty) that fails at runtime.

This commit detects the missing "longflag" element and reports the error at compile-time.

fixes #140

Author: lassoan

GenerateCLP/GenerateCLP.cxx

@@ -1339,6 +1339,7 @@ void GenerateTCLAPParse(std::ostream &sout, ModuleDescription &module)
   sout << "      std::ostringstream msg;" << EOL << std::endl;
 
   // Second pass generates TCLAP declarations
+  int longflagMissingCount = 0;
   std::vector<ModuleParameterGroup>::const_iterator git;
   std::vector<ModuleParameter>::const_iterator pit;
   for (git = module.GetParameterGroups().begin();
@@ -1356,6 +1357,8 @@ void GenerateTCLAPParse(std::ostream &sout, ModuleDescription &module)
         continue;
         }
 
+      bool longflagMissing = false;
+
       sout << "    msg.str(\"\");";
       sout << "msg << "
            << "\""
@@ -1389,6 +1392,10 @@ void GenerateTCLAPParse(std::ostream &sout, ModuleDescription &module)
 
       if (pit->GetCPPType() == "bool")
         {
+        if (pit->GetLongFlag().empty())
+          {
+          longflagMissing = true;
+          }
         sout << "    TCLAP::SwitchArg "
              << pit->GetName()
              << "Arg" << "(\""
@@ -1440,6 +1447,10 @@ void GenerateTCLAPParse(std::ostream &sout, ModuleDescription &module)
           }
         else if (IsEnumeration(*pit))
           {
+          if (pit->GetLongFlag().empty())
+            {
+            longflagMissing = true;
+            }
           sout << "    TCLAP::ValueArg<";
           sout << pit->GetCPPType();
           sout << "> "
@@ -1460,6 +1471,10 @@ void GenerateTCLAPParse(std::ostream &sout, ModuleDescription &module)
           }
         else
           {
+          if (pit->GetLongFlag().empty())
+            {
+            longflagMissing = true;
+            }
           if (pit->GetMultiple() == "true")
             {
             sout << "    TCLAP::MultiArg<";
@@ -1510,6 +1525,19 @@ void GenerateTCLAPParse(std::ostream &sout, ModuleDescription &module)
                << EOL << std::endl << EOL << std::endl;
           }
         }
+      if (longflagMissing)
+        {
+        std::cerr << "GenerateCLP: Warning: Required 'longflag' is not specified for parameter '" << pit->GetName() << "'." << std::endl;
+        longflagMissingCount++;
+        }
+      if (longflagMissingCount > 1)
+        {
+        // If only one parameter is missing a longflag, then TCLAP can still be used.
+        // However, multiple parameters missing longflags will cause TCLAP to throw an exception at runtime.
+        // It is better to report the error here, at compile time.
+        std::cerr << "GenerateCLP: Error: multiple parameters found with missing 'longflag'. Code generation aborted." << std::endl;
+        exit(EXIT_FAILURE);
+        }
       }
     }