Fix build, Add support for multiple values and empty values

build.bfg

@@ -9,12 +9,12 @@ project('flags', version='1.0pre')
 global_options(['-std=c++1z', '-Wall', '-Wextra', '-Werror', '-pedantic'],
                lang='c++')
 mettle = package('mettle')
-includes = header_directory('include', include='flags.h')
+includes = header_directory('include', include='*.h')
 driver = test_driver(
   'mettle -o verbose'
 )
 
-for src in find_files('test', '*.cc'):
+for src in find_files('test/*.cc'):
   path = os.path.join('test', src.path.basename())
   test(executable(
       splitext(path)[0],

include/flags.h

@@ -13,7 +13,7 @@
 namespace flags {
 namespace detail {
 using argument_map =
-    std::unordered_map<std::string_view, std::optional<std::string_view>>;
+    std::unordered_map<std::string_view, std::vector<std::optional<std::string_view>>>;
 
 // Non-destructively parses the argv tokens.
 // * If the token begins with a -, it will be considered an option.
@@ -38,6 +38,11 @@ struct parser {
  private:
   // Advance the state machine for the current token.
   void churn(const std::string_view& item) {
+    if(item.empty())
+    {
+      on_value(item);
+      return;
+    }
     item.at(0) == '-' ? on_option(item) : on_value(item);
   }
 
@@ -70,7 +75,8 @@ struct parser {
       return;
     }
     // Consume the preceding option and assign its value.
-    options_.emplace(*current_option_, value);
+    // operator[] will insert an empty vector if needed
+    options_[*current_option_].emplace_back(std::move(value));
     current_option_.reset();
   }
 
@@ -83,11 +89,21 @@ struct parser {
 inline std::optional<std::string_view> get_value(
     const argument_map& options, const std::string_view& option) {
   if (const auto it = options.find(option); it != options.end()) {
-    return it->second;
+    // If a key exists, there must be at least one value
+    return it->second[0];
   }
   return std::nullopt;
 }
 
+// If a key exists, return a vector with its values
+inline std::vector<std::optional<std::string_view>> get_values(
+    const argument_map& options, const std::string_view& option) {
+  if (const auto it = options.find(option); it != options.end()) {
+    return it->second;
+  }
+  return {};
+}
+
 // Coerces the string value of the given option into <T>.
 // If the value cannot be properly parsed or the key does not exist, returns
 // nullopt.
@@ -131,6 +147,62 @@ inline std::optional<bool> get(const argument_map& options,
   return std::nullopt;
 }
 
+// Coerces the string values of the given option into std::vector<T>.
+// If a value cannot be properly parsed it is not added. If there are
+// no suitable values or the key does not exist, returns nullopt.
+template <class T>
+std::vector<std::optional<T>> get_multiple(const argument_map& options,
+                                           const std::string_view& option) {
+  std::vector<std::optional<T>> values;
+  const auto views = get_values(options, option);
+  for (const auto &view : views) {
+    if (!view) {
+      values.push_back(std::nullopt);
+      continue;
+    }
+    if (T value; std::istringstream(std::string(*view)) >> value) {
+      values.push_back(value);
+    } else {
+      values.push_back(std::nullopt);
+    }
+  }
+  return values;
+}
+
+// Since the values are already stored as strings, there's no need to use `>>`.
+template <>
+inline std::vector<std::optional<std::string_view>> get_multiple(
+                  const argument_map& options, const std::string_view& option) {
+  return get_values(options, option);
+}
+
+template <>
+inline std::vector<std::optional<std::string>> get_multiple(
+                  const argument_map& options, const std::string_view& option) {
+  const auto views = get_values(options, option);
+  std::vector<std::optional<std::string>> values(views.begin(), views.end());
+  return values;
+}
+
+// Special case for booleans: if the value is in the falsities array (see get<bool>)
+// the option will be considered falsy. Otherwise, it will be considered truthy just
+// for being present.
+template <>
+inline std::vector<std::optional<bool>> get_multiple(
+                  const argument_map& options, const std::string_view& option) {
+  const auto views = get_values(options, option);
+  std::vector<std::optional<bool>> values;
+  for (const auto view : views) {
+    if (!view) {
+      values.push_back(true);
+      continue;
+    }
+    values.push_back(std::none_of(falsities.begin(), falsities.end(),
+                                  [&view](auto falsity) { return view == falsity; }));
+  }
+  return values;
+}
+
 // Coerces the string value of the given positional index into <T>.
 // If the value cannot be properly parsed or the key does not exist, returns
 // nullopt.
@@ -181,6 +253,22 @@ struct args {
     return get<T>(option).value_or(default_value);
   }
 
+  template <class T>
+  std::vector<std::optional<T>> get_multiple(const std::string_view& option) const {
+    return detail::get_multiple<T>(parser_.options(), option);
+  }
+
+  template <class T>
+  std::vector<T> get_multiple(const std::string_view& option, T&& default_value) const {
+    const auto items = get_multiple<T>(option);
+    std::vector<T> values;
+    values.reserve(items.size());
+    for(const auto& item : items) {
+      values.push_back(item ? *item : default_value);
+    }
+    return values;
+  }
+
   template <class T>
   std::optional<T> get(size_t positional_index) const {
     return detail::get<T>(parser_.positional_arguments(), positional_index);

test/flags.cc

@@ -5,6 +5,8 @@
 #include <stdexcept>
 #include <string>
 #include <string_view>
+#include <cstring>
+#include <algorithm>
 
 using namespace mettle;
 
@@ -39,6 +41,19 @@ char** initialize_argv(const std::initializer_list<const char*> args) {
   return argv;
 }
 
+// Same as above but using a std::vector
+char** initialize_argv(const std::vector<const char*>& args) {
+  char** argv =
+      reinterpret_cast<char**>(malloc((args.size() + 2) * sizeof(char*)));
+  initialize_arg(argv, 0, "TEST");
+  std::size_t i = 0;
+  for (const auto& arg : args) {
+    initialize_arg(argv, ++i, arg);
+  }
+  argv[args.size() + 1] = NULL;
+  return argv;
+}
+
 // Cleans up every item within argv, then argv itself.
 void cleanup_argv(char** argv) {
   size_t index = 0;
@@ -52,6 +67,9 @@ struct args_fixture {
   static args_fixture create(const std::initializer_list<const char*> args) {
     return {args.size(), initialize_argv(args)};
   }
+  static args_fixture create(const std::vector<const char*>& args) {
+    return {args.size(), initialize_argv(args)};
+  }
   ~args_fixture() { cleanup_argv(argv_); }
 
   size_t argc() const { return argc_; }
@@ -184,6 +202,56 @@ suite<> flag_parsing("flag parsing", [](auto& _) {
            equal_to(std::string(LOREM_IPSUM)));
   });
 
+  // Empty values
+  _.test("empty", [](){
+    const auto fixture = args_fixture::create({"--foo", ""});
+    expect(*fixture.args().get<std::string>("foo"), equal_to(""));
+  });
+
+  // Multiple values for one flag
+  _.test("multiple", [](){
+    const auto fixture = args_fixture::create({"--foo", "bar", "--foo", "baz"});
+    auto foo = fixture.args().get_multiple<std::string>("foo");
+    expect(foo.size(), equal_to(2));
+    expect(foo[0].value(), equal_to("bar"));
+    expect(foo[1].value(), equal_to("baz"));
+  });
+
+  _.test("multiple with type", [](){
+    const auto fixture = args_fixture::create({"-x", "-x", "1", "-x", "2"});
+    auto x = fixture.args().get_multiple<int>("x", 0);
+    expect(x.size(), equal_to(3));
+    expect(x[0], equal_to(0));
+    expect(x[1], equal_to(1));
+    expect(x[2], equal_to(2));
+  });
+
+  _.test("multiple falsities", [](){
+    std::vector<const char*> args;
+    for (const auto falsity : flags::detail::falsities) {
+      args.push_back("--foo");
+      args.push_back(falsity);
+    }
+    const auto fixture = args_fixture::create(args);
+    const auto foos1 = fixture.args().get_multiple<bool>("foo");
+    for (const auto& foo : foos1) {
+      expect(foo && *foo, equal_to(false));
+    }
+    const auto foos2 = fixture.args().get_multiple<bool>("foo", true);
+    for (const auto& foo : foos2) {
+      expect(foo, equal_to(false));
+    }
+  });
+
+  _.test("multiple valueless flags", [](){
+    const auto fixture = args_fixture::create({"--foo", "-foo", "--foo", "-foo"});
+    const auto foos = fixture.args().get_multiple<bool>("foo");
+    expect(foos.size(), equal_to(4));
+    for (const auto& foo : foos) {
+      expect(static_cast<bool>(foo), equal_to(true));
+    }
+  });
+
   // Basic number parsing. Verifying ints are truncated and doubles are
   // succesfully parsed.
   _.test("numbers", []() {