cmArgumentParser: Offer cm::optional bindings to capture keyword presence

Several clients have been using `keywordsMissingValue` or
`parsedKeywords` to check for the presence of keywords.  Offer them a
type-encoded way to explicitly check whether a keyword is present.

1 files changed, 11 insertions, 0 deletions

diff --git a/Source/cmArgumentParser.h b/Source/cmArgumentParser.h
index 2120a27..8be5a9c 100644
--- a/Source/cmArgumentParser.h
+++ b/Source/cmArgumentParser.h
@@ -10,6 +10,7 @@
 #include <utility>
 #include <vector>
 
+#include <cm/optional>
 #include <cm/string_view>
 #include <cmext/string_view>
 
@@ -39,6 +40,16 @@ public:
   void Bind(std::vector<std::string>& val);
   void Bind(std::vector<std::vector<std::string>>& val);
 
+  // cm::optional<> records the presence the keyword to which it binds.
+  template <typename T>
+  void Bind(cm::optional<T>& optVal)
+  {
+    if (!optVal) {
+      optVal.emplace();
+    }
+    this->Bind(*optVal);
+  }
+
   void Consume(cm::string_view arg, void* result,
                std::vector<std::string>* unparsedArguments,
                std::vector<cm::string_view>* keywordsMissingValue,