2 files changed, 30 insertions, 2 deletions

diff --git a/MCServer/Plugins/Debuggers/Debuggers.lua b/MCServer/Plugins/Debuggers/Debuggers.lua
index d0c362ab4..c8e96d378 100644
--- a/MCServer/Plugins/Debuggers/Debuggers.lua
+++ b/MCServer/Plugins/Debuggers/Debuggers.lua
@@ -62,6 +62,7 @@ function Initialize(Plugin)
 	TestStringBase64()
 	-- TestUUIDFromName()
 	-- TestRankMgr()
+	TestFileExt()
 
 	--[[
 	-- Test cCompositeChat usage in console-logging:
@@ -79,6 +80,18 @@ end;
 
 
 
+function TestFileExt()
+	assert(cFile:ChangeFileExt("fileless_dir/", "new") == "fileless_dir/")
+	assert(cFile:ChangeFileExt("pathless_file.ext", "new") == "pathless_file.new")
+	assert(cFile:ChangeFileExt("path/to/file.ext", "new") == "path/to/file.new")
+	assert(cFile:ChangeFileExt("path/to.dir/file", "new") == "path/to.dir/file.new")
+	assert(cFile:ChangeFileExt("path/to.dir/file.ext", "new") == "path/to.dir/file.new")
+end
+
+
+
+
+
 function TestPluginCalls()
 	-- In order to test the inter-plugin communication, we're going to call Core's ReturnColorFromChar() function
 	-- It is a rather simple function that doesn't need any tables as its params and returns a value, too
diff --git a/src/OSSupport/File.cpp b/src/OSSupport/File.cpp
index 7ad1b3f81..fcd5ec027 100644
--- a/src/OSSupport/File.cpp
+++ b/src/OSSupport/File.cpp
@@ -456,10 +456,25 @@ AString cFile::ReadWholeFile(const AString & a_FileName)
 AString cFile::ChangeFileExt(const AString & a_FileName, const AString & a_NewExt)
 {
 	auto res = a_FileName;
+
+	// If the path separator is the last character of the string, return the string unmodified (refers to a folder):
+	#ifdef _WIN32
+		auto LastPathSep = res.find_last_of("/\\");  // Find either path separator - Windows accepts slashes as separators, too
+	#else
+		auto LastPathSep = res.rfind('/');
+	#endif
+	if ((LastPathSep != AString::npos) && (LastPathSep + 1 == res.size()))
+	{
+		return res;
+	}
+
 	auto DotPos = res.rfind('.');
-	if (DotPos == AString::npos)
+	if (
+		(DotPos == AString::npos) ||  // No dot found
+		((LastPathSep != AString::npos) && (LastPathSep > DotPos))  // Last dot is before the last path separator (-> in folder name)
+	)
 	{
-		// No extension, just append it:
+		// No extension, just append the new one:
 		res.push_back('.');
 		res.append(a_NewExt);
 	}