feat: throw error when encounters duplicate key

Author: David Chu

ini/INIReader.h

@@ -408,9 +408,11 @@ inline const bool INIReader::BoolConverter(std::string s) const {
 inline int INIReader::ValueHandler(void* user, const char* section,
                                    const char* name, const char* value) {
     INIReader* reader = (INIReader*)user;
-    if (reader->_values[section][name].size() > 0)
-        reader->_values[section][name] += "\n";
-    reader->_values[section][name] += value;
+    if (reader->_values[section][name].size() > 0) {
+        throw std::runtime_error("duplicate key '" + std::string(name) +
+                                 "' in section '" + section + "'.");
+    }
+    reader->_values[section][name] = value;
     return 1;
 }
 }

test/fixtures/duplicate_keys.ini

@@ -0,0 +1,4 @@
+[bad_section]
+foo = hello
+bar = 42
+foo = world

test/tests.cpp

@@ -108,3 +108,8 @@ TEST(INIReader, read_big_file) {
         EXPECT_EQ(v, i);
     }
 }
+
+TEST(INIReader, dulicate_keys) {
+    EXPECT_THROW(INIReader r{"./fixtures/duplicate_keys.ini"},
+                 std::runtime_error);
+}