From 20095a697ae6060a02e8adb466e476bd255abf3e Mon Sep 17 00:00:00 2001
From: Pranav Srinivas Kumar <pranav.srinivas.kumar@gmail.com>
Date: Wed, 21 Sep 2022 06:54:34 -0700
Subject: [PATCH] Added option=value support using #185

---
 include/argparse/argparse.hpp | 37 +++++++++++++++++++++++++++++++++--
 test/CMakeLists.txt           |  1 +
 test/test_equals_form.cpp     | 31 +++++++++++++++++++++++++++++
 3 files changed, 67 insertions(+), 2 deletions(-)
 create mode 100644 test/test_equals_form.cpp

diff --git a/include/argparse/argparse.hpp b/include/argparse/argparse.hpp
index f8d84f9..8235ba8 100644
--- a/include/argparse/argparse.hpp
+++ b/include/argparse/argparse.hpp
@@ -1226,10 +1226,42 @@ public:
   }
 
 private:
+  /*
+   * Pre-process this argument list. Anything starting with "--", that
+   * contains an =, where the prefix before the = has an entry in the
+   * options table, should be split.
+   */
+  std::vector<std::string>
+  preprocess_arguments(const std::vector<std::string> &raw_arguments) {
+    std::vector<std::string> arguments;
+    for (const auto &arg : raw_arguments) {
+      // Check that:
+      // - We don't have an argument named exactly this
+      // - The argument starts with "--"
+      // - The argument contains a "="
+      std::size_t eqpos = arg.find("=");
+      if (m_argument_map.find(arg) == m_argument_map.end() &&
+          arg.rfind("--", 0) == 0 && eqpos != std::string::npos) {
+        // Get the name of the potential option, and check it exists
+        std::string opt_name = arg.substr(0, eqpos);
+        if (m_argument_map.find(opt_name) != m_argument_map.end()) {
+          // This is the name of an option! Split it into two parts
+          arguments.push_back(std::move(opt_name));
+          arguments.push_back(arg.substr(eqpos + 1));
+          continue;
+        }
+      }
+      // If we've fallen through to here, then it's a standard argument
+      arguments.push_back(arg);
+    }
+    return arguments;
+  }
+
   /*
    * @throws std::runtime_error in case of any invalid argument
    */
-  void parse_args_internal(const std::vector<std::string> &arguments) {
+  void parse_args_internal(const std::vector<std::string> &raw_arguments) {
+    auto arguments = preprocess_arguments(raw_arguments);
     if (m_program_name.empty() && !arguments.empty()) {
       m_program_name = arguments.front();
     }
@@ -1294,7 +1326,8 @@ private:
    * Like parse_args_internal but collects unused args into a vector<string>
    */
   std::vector<std::string>
-  parse_known_args_internal(const std::vector<std::string> &arguments) {
+  parse_known_args_internal(const std::vector<std::string> &raw_arguments) {
+    auto arguments = preprocess_arguments(raw_arguments);
 
     std::vector<std::string> unknown_arguments{};
 
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index b57da7d..dd7aecc 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -48,6 +48,7 @@ file(GLOB ARGPARSE_TEST_SOURCES
     test_version.cpp
     test_subparsers.cpp
     test_parse_known_args.cpp
+    test_equals_form.cpp
 )
 set_source_files_properties(main.cpp
     PROPERTIES
diff --git a/test/test_equals_form.cpp b/test/test_equals_form.cpp
new file mode 100644
index 0000000..e09b664
--- /dev/null
+++ b/test/test_equals_form.cpp
@@ -0,0 +1,31 @@
+#include <argparse/argparse.hpp>
+#include <doctest.hpp>
+#include <iostream>
+using doctest::test_suite;
+
+TEST_CASE("Basic --value=value" * test_suite("equals_form")) {
+  argparse::ArgumentParser parser("test");
+  parser.add_argument("--long");
+  parser.parse_args({"test", "--long=value"});
+  std::string result{parser.get("--long")};
+  REQUIRE(result == "value");
+}
+
+TEST_CASE("Fallback = in regular option name" * test_suite("equals_form")) {
+  argparse::ArgumentParser parser("test");
+  parser.add_argument("--long=mislead");
+  parser.parse_args({"test", "--long=mislead", "value"});
+  std::string result{parser.get("--long=mislead")};
+  REQUIRE(result == "value");
+}
+
+TEST_CASE("Duplicate =-named and standard" * test_suite("equals_form")) {
+  argparse::ArgumentParser parser("test");
+  parser.add_argument("--long=mislead");
+  parser.add_argument("--long").default_value(std::string{"NO_VALUE"});
+  parser.parse_args({"test", "--long=mislead", "value"});
+  std::string result{parser.get("--long=mislead")};
+  REQUIRE(result == "value");
+  std::string result2{parser.get("--long")};
+  REQUIRE(result2 == "NO_VALUE");
+}
\ No newline at end of file