Add an ability to handle multiple config files

README.md

@@ -747,6 +747,14 @@ Spaces before and after the name and argument are ignored. Multiple arguments ar
 To print a configuration file from the passed
 arguments, use `.config_to_str(default_also=false, write_description=false)`, where `default_also` will also show any defaulted arguments, and `write_description` will include the app and option descriptions.  See [Config files](https://cliutils.github.io/CLI11/book/chapters/config.html) for some additional details.
 
+If it is desired that multiple configuration be allowed.  Use
+
+```cpp
+app.set_config("--config")->expected(1, X);
+```
+
+Where X is some positive number and will allow up to `X` configuration files to be specified by separate `--config` arguments.
+
 ### Inheriting defaults
 
 Many of the defaults for subcommands and even options are inherited from their creators. The inherited default values for subcommands are `allow_extras`, `prefix_command`, `ignore_case`, `ignore_underscore`, `fallthrough`, `group`, `footer`,`immediate_callback` and maximum number of required subcommands. The help flag existence, name, and description are inherited, as well.

book/chapters/config.md

@@ -78,6 +78,16 @@ sub.subcommand = true
 
 The main differences are in vector notation and comment character.  Note: CLI11 is not a full TOML parser as it just reads values as strings.  It is possible (but not recommended) to mix notation.
 
+## Multiple configuration files
+
+If it is desired that multiple configuration be allowed.  Use
+
+```cpp
+app.set_config("--config")->expected(1, X);
+```
+
+Where X is some positive integer and will allow up to `X` configuration files to be specified by separate `--config` arguments.
+
 ## Writing out a configure file
 
 To print a configuration file from the passed arguments, use `.config_to_str(default_also=false, write_description=false)`, where `default_also` will also show any defaulted arguments, and `write_description` will include option descriptions and the App description

include/CLI/App.hpp

@@ -2053,29 +2053,31 @@ class App {
     void _process_config_file() {
         if(config_ptr_ != nullptr) {
             bool config_required = config_ptr_->get_required();
-            bool file_given = config_ptr_->count() > 0;
-            auto config_file = config_ptr_->as<std::string>();
-            if(config_file.empty()) {
+            auto file_given = config_ptr_->count() > 0;
+            auto config_files = config_ptr_->as<std::vector<std::string>>();
+            if(config_files.empty() || config_files.front().empty()) {
                 if(config_required) {
                     throw FileError::Missing("no specified config file");
                 }
                 return;
             }
-
-            auto path_result = detail::check_path(config_file.c_str());
-            if(path_result == detail::path_type::file) {
-                try {
-                    std::vector<ConfigItem> values = config_formatter_->from_file(config_file);
-                    _parse_config(values);
-                    if(!file_given) {
-                        config_ptr_->add_result(config_file);
+            for(auto rit = config_files.rbegin(); rit != config_files.rend(); ++rit) {
+                const auto &config_file = *rit;
+                auto path_result = detail::check_path(config_file.c_str());
+                if(path_result == detail::path_type::file) {
+                    try {
+                        std::vector<ConfigItem> values = config_formatter_->from_file(config_file);
+                        _parse_config(values);
+                        if(!file_given) {
+                            config_ptr_->add_result(config_file);
+                        }
+                    } catch(const FileError &) {
+                        if(config_required || file_given)
+                            throw;
                     }
-                } catch(const FileError &) {
-                    if(config_required || file_given)
-                        throw;
+                } else if(config_required || file_given) {
+                    throw FileError::Missing(config_file);
                 }
-            } else if(config_required || file_given) {
-                throw FileError::Missing(config_file);
             }
         }
     }

tests/ConfigFileTest.cpp

@@ -591,6 +591,89 @@ TEST_F(TApp, IniNotRequiredNotDefault) {
     EXPECT_EQ(app.get_config_ptr()->as<std::string>(), tmpini2.c_str());
 }
 
+TEST_F(TApp, MultiConfig) {
+
+    TempFile tmpini{"TestIniTmp.ini"};
+    TempFile tmpini2{"TestIniTmp2.ini"};
+
+    app.set_config("--config")->expected(1, 3);
+
+    {
+        std::ofstream out{tmpini};
+        out << "[default]" << std::endl;
+        out << "two=99" << std::endl;
+        out << "three=3" << std::endl;
+    }
+
+    {
+        std::ofstream out{tmpini2};
+        out << "[default]" << std::endl;
+        out << "one=55" << std::endl;
+        out << "three=4" << std::endl;
+    }
+
+    int one{0}, two{0}, three{0};
+    app.add_option("--one", one);
+    app.add_option("--two", two);
+    app.add_option("--three", three);
+
+    args = {"--config", tmpini2, "--config", tmpini};
+    run();
+
+    EXPECT_EQ(99, two);
+    EXPECT_EQ(3, three);
+    EXPECT_EQ(55, one);
+
+    args = {"--config", tmpini, "--config", tmpini2};
+    run();
+
+    EXPECT_EQ(99, two);
+    EXPECT_EQ(4, three);
+    EXPECT_EQ(55, one);
+}
+
+TEST_F(TApp, MultiConfig_single) {
+
+    TempFile tmpini{"TestIniTmp.ini"};
+    TempFile tmpini2{"TestIniTmp2.ini"};
+
+    app.set_config("--config")->multi_option_policy(CLI::MultiOptionPolicy::TakeLast);
+
+    {
+        std::ofstream out{tmpini};
+        out << "[default]" << std::endl;
+        out << "two=99" << std::endl;
+        out << "three=3" << std::endl;
+    }
+
+    {
+        std::ofstream out{tmpini2};
+        out << "[default]" << std::endl;
+        out << "one=55" << std::endl;
+        out << "three=4" << std::endl;
+    }
+
+    int one{0}, two{0}, three{0};
+    app.add_option("--one", one);
+    app.add_option("--two", two);
+    app.add_option("--three", three);
+
+    args = {"--config", tmpini2, "--config", tmpini};
+    run();
+
+    EXPECT_EQ(99, two);
+    EXPECT_EQ(3, three);
+    EXPECT_EQ(0, one);
+
+    two = 0;
+    args = {"--config", tmpini, "--config", tmpini2};
+    run();
+
+    EXPECT_EQ(0, two);
+    EXPECT_EQ(4, three);
+    EXPECT_EQ(55, one);
+}
+
 TEST_F(TApp, IniRequiredNotFound) {
 
     std::string noini = "TestIniNotExist.ini";

tests/TransformTest.cpp

@@ -7,6 +7,7 @@
 #include "app_helper.hpp"
 
 #include <array>
+#include <chrono>
 #include <cstdint>
 #include <unordered_map>
 
@@ -850,6 +851,22 @@ TEST_F(TApp, AsSizeValue1000_1024) {
     EXPECT_EQ(value, ki_value);
 }
 
+TEST_F(TApp, duration_test) {
+    std::chrono::seconds duration{1};
+
+    app.option_defaults()->ignore_case();
+    app.add_option_function<std::size_t>(
+           "--duration",
+           [&](size_t a_value) { duration = std::chrono::seconds{a_value}; },
+           "valid units: sec, min, h, day.")
+        ->capture_default_str()
+        ->transform(CLI::AsNumberWithUnit(
+            std::map<std::string, std::size_t>{{"sec", 1}, {"min", 60}, {"h", 3600}, {"day", 24 * 3600}}));
+    EXPECT_NO_THROW(app.parse(std::vector<std::string>{"1 day", "--duration"}));
+
+    EXPECT_EQ(duration, std::chrono::seconds(86400));
+}
+
 TEST_F(TApp, AsSizeValue1024) {
     std::uint64_t value{0};
     app.add_option("-s", value)->transform(CLI::AsSizeValue(false));