Implemented API and tests for programming implicit values in toggle arguments

src/argparse.hpp

@@ -42,6 +42,7 @@ struct Argument {
   std::vector<std::string> mNames;
   std::string mHelp;
   std::any mDefaultValue;
+  std::any mImplicitValue;
   std::function<std::any(const std::string&)> mAction;
   std::vector<std::any> mValues;
   std::vector<std::string> mRawValues;
@@ -67,6 +68,11 @@ struct Argument {
     return *this;
   }
 
+  Argument& implicit_value(std::any aImplicitValue) {
+    mImplicitValue = aImplicitValue;
+    return *this;
+  }
+
   Argument& action(std::function<std::any(const std::string&)> aAction) {
     mAction = aAction;
     return *this;
@@ -176,8 +182,20 @@ class ArgumentParser {
         auto tCurrentArgument = argv[i];
         std::map<std::string, std::shared_ptr<Argument>>::iterator tIterator = mArgumentMap.find(argv[i]);
         if (tIterator != mArgumentMap.end()) {
+          // Start parsing optional argument
           auto tArgument = tIterator->second;
           auto tCount = tArgument->mNumArgs;
+
+          // Check to see if implicit value should be used
+          // Two cases to handle here:
+          // (1) User has explicitly programmed nargs to be 0
+          // (2) User has left nargs to be default, i.e., 1 and provided an implicit value
+          if (tCount == 0 || (tArgument->mImplicitValue.has_value() && tCount == 1)) {
+            // Use implicit value for this optional argument
+            tArgument->mValues.push_back(tArgument->mImplicitValue);
+            tArgument->mRawValues.push_back("");
+            tCount = 0;
+          }
           while (tCount > 0) {
             i = i + 1;
             if (i < argc) {

tests/main.cpp

@@ -4,3 +4,4 @@
 #include <test_add_argument.hpp>
 #include <test_parse_args.hpp>
 #include <test_positional_arguments.hpp>
+#include <test_implicit_values.hpp>

tests/test_implicit_values.hpp

@@ -0,0 +1,27 @@
+#pragma once
+#include <catch.hpp>
+#include <argparse.hpp>
+
+TEST_CASE("Parse toggle arguments with default value", "[parse_args]") {
+  argparse::ArgumentParser program("test");
+  program.add_argument("--verbose", "-v")
+    .default_value(false)
+    .implicit_value(true);
+
+  program.parse_args({ "./test.exe" });
+  auto arguments = program.get_arguments();
+  REQUIRE(arguments.size() == 2);
+  REQUIRE(program.get<bool>("--verbose") == false);
+}
+
+TEST_CASE("Parse toggle arguments with implicit value", "[parse_args]") {
+  argparse::ArgumentParser program("test");
+  program.add_argument("--verbose")
+    .default_value(false)
+    .implicit_value(true);
+
+  program.parse_args({ "./test.exe", "--verbose" });
+  auto arguments = program.get_arguments();
+  REQUIRE(arguments.size() == 1);
+  REQUIRE(program.get<bool>("--verbose") == true);
+}