Default --help to print help and exit

include/argparse.hpp

@@ -30,6 +30,7 @@ SOFTWARE.
 #pragma once
 #include <algorithm>
 #include <any>
+#include <cstdlib>
 #include <functional>
 #include <iostream>
 #include <iterator>
@@ -372,20 +373,15 @@ class Argument {
  bool mIsOptional : 1;
  bool mIsRequired : 1;
  bool mIsUsed : 1; // True if the optional argument is used by user
-
- static constexpr auto mHelpOption = "-h";
- static constexpr auto mHelpOptionLong = "--help";
 };
 
 class ArgumentParser {
 public:
  explicit ArgumentParser(std::string aProgramName = {})
  : mProgramName(std::move(aProgramName)) {
- add_argument(Argument::mHelpOption, Argument::mHelpOptionLong)
+ add_argument("-h", "--help")
  .help("show this help message and exit")
- .nargs(0)
- .default_value(false)
- .implicit_value(true);
+ .nargs(0);
  }
 
  ArgumentParser(ArgumentParser &&) noexcept = default;
@@ -542,20 +538,26 @@ class ArgumentParser {
  auto positionalArgumentIt = std::begin(mPositionalArguments);
  for (auto it = std::next(std::begin(aArguments)); it != end;) {
  const auto &tCurrentArgument = *it;
- if (tCurrentArgument == Argument::mHelpOption ||
- tCurrentArgument == Argument::mHelpOptionLong) {
- throw std::runtime_error("help called");
- }
  if (Argument::is_positional(tCurrentArgument)) {
  if (positionalArgumentIt == std::end(mPositionalArguments)) {
  throw std::runtime_error(
  "Maximum number of positional arguments exceeded");
  }
  auto tArgument = positionalArgumentIt++;
  it = tArgument->consume(it, end);
- } else if (auto tIterator = mArgumentMap.find(tCurrentArgument);
- tIterator != mArgumentMap.end()) {
+ continue;
+ }
+
+ auto tIterator = mArgumentMap.find(tCurrentArgument);
+ if (tIterator != mArgumentMap.end()) {
  auto tArgument = tIterator->second;
+
+ // the first optional argument is --help
+ if (tArgument == mOptionalArguments.begin()) {
+ std::cout << *this;
+ std::exit(0);
+ }
+
  it = tArgument->consume(std::next(it), end, tCurrentArgument);
  } else if (const auto &tCompoundArgument = tCurrentArgument;
  tCompoundArgument.size() > 1 && tCompoundArgument[0] == '-' &&
@@ -607,7 +609,7 @@ class ArgumentParser {
 
  void index_argument(list_iterator argIt) {
  for (auto &mName : std::as_const(argIt->mNames))
- mArgumentMap.emplace(mName, argIt);
+ mArgumentMap.insert_or_assign(mName, argIt);
  }
 
  std::string mProgramName;

test/test_help.cpp

@@ -17,3 +17,27 @@ TEST_CASE("Users can format help message" * test_suite("help")) {
  auto msg = program.help().str();
  REQUIRE(msg == s.str());
 }
+
+TEST_CASE("Users can override the help options" * test_suite("help")) {
+ GIVEN("a program that meant to take -h as a normal option") {
+ argparse::ArgumentParser program("test");
+ program.add_argument("input");
+ program.add_argument("-h").implicit_value('h').default_value('x');
+
+ WHEN("provided -h without fulfilling other requirements") {
+ THEN("validation fails") {
+ REQUIRE_THROWS_AS(program.parse_args({"test", "-h"}),
+ std::runtime_error);
+ }
+ }
+
+ WHEN("provided arguments to all parameters") {
+ program.parse_args({"test", "-h", "some input"});
+
+ THEN("these parameters get their values") {
+ REQUIRE(program["-h"] == 'h');
+ REQUIRE(program.get("input") == "some input");
+ }
+ }
+ }
+}