fix handling of 1 line multi-line quoted strings

README.md

@@ -288,8 +288,7 @@ want, and afterward, using `count`, you can use any of the names, with dashes as
 needed, to count the options. One of the names is allowed to be given without
 proceeding dash(es); if present the option is a positional option, and that name
 will be used on the help line for its positional form. The string `++` is also
-not allowed as option name due to is use in some unusual cases as an array
-separator and marker on config files.
+not allowed as option name due to its use as an array separator and marker on config files.
 
 The `add_option_function<type>(...` function will typically require the template
 parameter be given unless a `std::function` object with an exact match is

include/CLI/impl/Config_inl.hpp

@@ -322,6 +322,21 @@ inline std::vector<ConfigItem> ConfigBase::from_config(std::istream &input) cons
                     item.pop_back();
                     lineExtension = true;
                 }
+                else if (detail::hasMLString(item,keyChar))
+                {
+                    //deal with the first line closing the multiline literal
+                    item.pop_back();
+                    item.pop_back();
+                    item.pop_back();
+                    if(keyChar == '\"') {
+                        try {
+                            item = detail::remove_escaped_characters(item);
+                        } catch(const std::invalid_argument &iarg) {
+                            throw CLI::ParseError(iarg.what(), CLI::ExitCodes::InvalidError);
+                        }
+                    }
+                    inMLineValue=false;
+                }
                 while(inMLineValue) {
                     std::string l2;
                     if(!std::getline(input, l2)) {

tests/AppTest.cpp

@@ -2075,7 +2075,7 @@ TEST_CASE_METHOD(TApp, "EnvOnly", "[app]") {
 // reported bug #1013 on github
 TEST_CASE_METHOD(TApp, "groupEnvRequired", "[app]") {
     std::string str;
-    auto group1 = app.add_option_group("group1");
+    auto *group1 = app.add_option_group("group1");
     put_env("CLI11_TEST_GROUP_REQUIRED", "string_abc");
     group1->add_option("-f", str, "f")->envname("CLI11_TEST_GROUP_REQUIRED")->required();
 

tests/FuzzFailTest.cpp

@@ -154,7 +154,7 @@ TEST_CASE("app_roundtrip") {
     CLI::FuzzApp fuzzdata2;
     auto app = fuzzdata.generateApp();
     auto app2 = fuzzdata2.generateApp();
-    int index = GENERATE(range(1, 4));
+    int index = GENERATE(range(1, 5));
     std::string optionString, flagString;
     auto parseData = loadFailureFile("round_trip_fail", index);
     if(parseData.size() > 25) {

tests/fuzzFail/round_trip_fail4

@@ -0,0 +1 @@
+'B"(zzzzzz!t0!!!!!--satd!!!!!!!!!--vopt0!!!!!--satd!!!]!!!!!--vopt0-b!!!b!!'B"(zzzzzz!t0!!!!!--satd!!!!!!!!!--vopt0!!!!!--satd!!!]!!!!!--vopt0-b!-bb-satd!!