Add value name to ProgramOptions::Option::requiresValue() member function

This value name is displayed in operator<<(ostream, ProgramOptions&)
when a option requires a value.

src/base/program_options.cpp

@@ -134,7 +134,7 @@ void ProgramOptions::parse(int argc, const char* argv[])
             if (i+1 >= argc) {
               stringstream msg;
               msg << "Missing value in '--" << optionName
-                  << "'=VALUE option specification";
+                  << "=" << option->getValueName() << "' option specification";
               throw ProgramOptionNeedsValue(msg.str());
             }
             optionValue = argv[++i];
@@ -173,7 +173,10 @@ std::ostream& operator<<(std::ostream& os, const base::ProgramOptions& po)
   for (base::ProgramOptions::OptionList::const_iterator
          it=po.options().begin(), end=po.options().end(); it != end; ++it) {
     const base::ProgramOptions::Option* option = *it;
-    size_t optionWidth = std::min<int>(26, 6+option->name().size()+1);
+    size_t optionWidth =
+      std::min<int>(26, 6+option->name().size()+1+
+                        (option->doesRequireValue() ? option->getValueName().size()+1: 0));
+
     if (maxOptionWidth < optionWidth)
       maxOptionWidth = optionWidth;
   }
@@ -181,13 +184,16 @@ std::ostream& operator<<(std::ostream& os, const base::ProgramOptions& po)
   for (base::ProgramOptions::OptionList::const_iterator
          it=po.options().begin(), end=po.options().end(); it != end; ++it) {
     const base::ProgramOptions::Option* option = *it;
-    size_t optionWidth = 6+option->name().size()+1;
+    size_t optionWidth = 6+option->name().size()+1+
+      (option->doesRequireValue() ? option->getValueName().size()+1: 0);
 
     if (option->mnemonic() != 0)
       os << setw(3) << '-' << option->mnemonic() << ", ";
     else
       os << setw(6) << ' ';
     os << "--" << option->name();
+    if (option->doesRequireValue())
+      os << " " << option->getValueName();
 
     if (!option->description().empty()) {
       bool multilines = (option->description().find('\n') != string::npos);

src/base/program_options.h

@@ -39,20 +39,23 @@ namespace base {
       Option(const std::string& name)
         : m_name(name)
         , m_mnemonic(0)
-        , m_enabled(false)
+        , m_enabled(false) {
-        , m_requiresValue(false) {
       }
       // Getters
       const std::string& name() const { return m_name; }
       const std::string& description() const { return m_description; }
       const std::string& value() const { return m_value; }
+      const std::string& getValueName() const { return m_valueName; }
       char mnemonic() const { return m_mnemonic; }
       bool enabled() const { return m_enabled; }
-      bool doesRequireValue() const { return m_requiresValue; }
+      bool doesRequireValue() const { return !m_valueName.empty(); }
       // Setters
       Option& description(const std::string& desc) { m_description = desc; return *this; }
       Option& mnemonic(char mnemonic) { m_mnemonic = mnemonic; return *this; }
-      Option& requiresValue() { m_requiresValue = true; return *this; }
+      Option& requiresValue(const std::string& valueName) {
+        m_valueName = valueName;
+        return *this;
+      }
     private:
       void setValue(const std::string& value) { m_value = value; }
       void setEnabled(bool enabled) { m_enabled = enabled; }
@@ -60,9 +63,9 @@ namespace base {
       std::string m_name;        // Name of the option (e.g. "help" for "--help")
       std::string m_description; // Description of the option (this can be used when the help is printed).
       std::string m_value;       // The value specified by the user in the command line.
+      std::string m_valueName;   // Empty if this option doesn't require a value, or the name of the expected value.
       char m_mnemonic;           // One character that can be used in the command line to use this option.
       bool m_enabled;            // True if the user specified this argument.
-      bool m_requiresValue;      // True if this option needs another argument.
 
       friend class ProgramOptions;
     };

src/base/program_options_unittest.cpp

@@ -16,7 +16,7 @@ TEST(ProgramOptions, OptionMembers)
   ProgramOptions::Option& help =
     po.add("help").mnemonic('h').description("Show the help");
   ProgramOptions::Option& output =
-    po.add("output").mnemonic('O').requiresValue();
+    po.add("output").mnemonic('O').requiresValue("OUTPUT");
 
   EXPECT_EQ("help", help.name());
   EXPECT_EQ("Show the help", help.description());
@@ -35,7 +35,7 @@ TEST(ProgramOptions, Reset)
 {
   ProgramOptions po;
   ProgramOptions::Option& help = po.add("help");
-  ProgramOptions::Option& file = po.add("file").requiresValue();
+  ProgramOptions::Option& file = po.add("file").requiresValue("FILE");
   EXPECT_FALSE(help.enabled());
   EXPECT_FALSE(file.enabled());
   EXPECT_EQ("", file.value());
@@ -56,8 +56,8 @@ TEST(ProgramOptions, Parse)
 {
   ProgramOptions po;
   ProgramOptions::Option& help = po.add("help").mnemonic('?');
-  ProgramOptions::Option& input = po.add("input").mnemonic('i').requiresValue();
+  ProgramOptions::Option& input = po.add("input").mnemonic('i').requiresValue("INPUT");
-  ProgramOptions::Option& output = po.add("output").mnemonic('o').requiresValue();
+  ProgramOptions::Option& output = po.add("output").mnemonic('o').requiresValue("OUTPUT");
 
   const char* argv1[] = { "program.exe", "-?" };
   po.parse(2, argv1);
@@ -111,8 +111,8 @@ TEST(ProgramOptions, ParseErrors)
 {
   ProgramOptions po;
   ProgramOptions::Option& help = po.add("help").mnemonic('?');
-  ProgramOptions::Option& input = po.add("input").mnemonic('i').requiresValue();
+  ProgramOptions::Option& input = po.add("input").mnemonic('i').requiresValue("INPUT");
-  ProgramOptions::Option& output = po.add("output").mnemonic('o').requiresValue();
+  ProgramOptions::Option& output = po.add("output").mnemonic('o').requiresValue("OUTPUT");
 
   const char* argv1[] = { "program.exe", "--input" };
   EXPECT_THROW(po.parse(2, argv1), ProgramOptionNeedsValue);