StringUtil: Modernize SplitString and add unit tests

Source/Core/Common/StringUtil.cpp

@@ -16,6 +16,7 @@
 #include <iterator>
 #include <limits.h>
 #include <locale>
+#include <ranges>
 #include <sstream>
 #include <string>
 #include <type_traits>
@@ -356,16 +357,17 @@ std::string PathToFileName(std::string_view path)
   return file_name + extension;
 }
 
-std::vector<std::string> SplitString(const std::string& str, const char delim)
+std::vector<std::string> SplitString(std::string_view sv, const char delim)
 {
-  std::istringstream iss(str);
-  std::vector<std::string> output(1);
+  if (sv.empty())
+    return {std::string()};
 
-  while (std::getline(iss, *output.rbegin(), delim))
-    output.push_back("");
+  const std::ranges::split_view string_views(sv, delim);
+  std::ranges::transform_view strings(string_views,
+                                      [](auto&& r) { return std::string(r.data(), r.size()); });
 
-  output.pop_back();
-  return output;
+  // TODO: Use C++23 std::from_range
+  return {strings.begin(), strings.end()};
 }
 
 std::string TabsToSpaces(int tab_size, std::string str)

Source/Core/Common/StringUtil.h

@@ -199,7 +199,7 @@ std::from_chars_result FromChars(std::string_view sv, T& value,
 
 std::string TabsToSpaces(int tab_size, std::string str);
 
-std::vector<std::string> SplitString(const std::string& str, char delim);
+std::vector<std::string> SplitString(std::string_view sv, char delim);
 
 // "C:/Windows/winhelp.exe" to "C:/Windows/", "winhelp", ".exe"
 // This requires forward slashes to be used for the path separators, even on Windows.

Source/UnitTests/Common/StringUtilTest.cpp

@@ -192,3 +192,35 @@ TEST(StringUtil, SplitPathBackslashesNotRecognizedAsSeparators)
 }
 
 // TODO: add `SplitPath` test coverage for paths containing Windows drives, e.g., "C:".
+
+TEST(StringUtil, SplitString)
+{
+  using V = std::vector<std::string>;
+  const char d = ',';
+  EXPECT_EQ(SplitString("", d), V({""}));
+  EXPECT_EQ(SplitString("a", d), V({"a"}));
+  EXPECT_EQ(SplitString("ab", d), V({"ab"}));
+  EXPECT_EQ(SplitString(",", d), V({"", ""}));
+  EXPECT_EQ(SplitString("a,", d), V({"a", ""}));
+  EXPECT_EQ(SplitString(",b", d), V({"", "b"}));
+  EXPECT_EQ(SplitString("a,b", d), V({"a", "b"}));
+  EXPECT_EQ(SplitString("ab,", d), V({"ab", ""}));
+  EXPECT_EQ(SplitString(",ab", d), V({"", "ab"}));
+  EXPECT_EQ(SplitString("ab,,", d), V({"ab", "", ""}));
+  EXPECT_EQ(SplitString(",ab,", d), V({"", "ab", ""}));
+  EXPECT_EQ(SplitString(",,ab", d), V({"", "", "ab"}));
+  EXPECT_EQ(SplitString("a,,", d), V({"a", "", ""}));
+  EXPECT_EQ(SplitString("a,b,", d), V({"a", "b", ""}));
+  EXPECT_EQ(SplitString("a,,c", d), V({"a", "", "c"}));
+  EXPECT_EQ(SplitString(",b,", d), V({"", "b", ""}));
+  EXPECT_EQ(SplitString(",b,c", d), V({"", "b", "c"}));
+  EXPECT_EQ(SplitString(",,c", d), V({"", "", "c"}));
+  EXPECT_EQ(SplitString(",,", d), V({"", "", ""}));
+  EXPECT_EQ(SplitString("abc", d), V({"abc"}));
+  EXPECT_EQ(SplitString("a,bc", d), V({"a", "bc"}));
+  EXPECT_EQ(SplitString("ab,c", d), V({"ab", "c"}));
+  EXPECT_EQ(SplitString("abc,", d), V({"abc", ""}));
+  EXPECT_EQ(SplitString(",abc", d), V({"", "abc"}));
+  EXPECT_EQ(SplitString("abc,,", d), V({"abc", "", ""}));
+  EXPECT_EQ(SplitString(",,abc", d), V({"", "", "abc"}));
+}