Merge pull request #166 from nzbgetcom/fix/unpack-err-messages

- added Zip exit codes decoder according to 7-Zip [doc](https://documentation.help/7-Zip/exit_codes.htm);
- added warning text that SevenZipCmd may not be valid, in case of problems with installing extensions;

daemon/extension/ExtensionManager.cpp

@@ -111,16 +111,16 @@ namespace ExtensionManager
 		};
 		unpacker.SetArgs(std::move(args));
 
-		int res = unpacker.Execute();
+		int ec = unpacker.Execute();
 
-		if (res != 0)
+		if (ec < 0)
 		{
-			if (!FileSystem::DeleteFile(filename.c_str()))
-			{
-				return "Failed to unpack and delete temp file: " + filename;
-			}
+			return "Failed to unpack " + filename + ". Make sure that the path to 7-Zip is valid.";
+		}
 
-			return "Failed to unpack " + filename;
+		if (ec > 0)
+		{
+			return "Failed to unpack " + filename + ". " + UnpackController::DecodeSevenZipExitCode(ec);
 		}
 
 		if (!FileSystem::DeleteFile(filename.c_str()))

daemon/postprocess/Unpack.cpp

@@ -961,3 +961,33 @@ bool UnpackController::HasCompletedArchiveFiles(NzbInfo* nzbInfo)
 
 	return false;
 }
+
+const char* UnpackController::DecodeSevenZipExitCode(int ec)
+{
+	// 7-Zip exit codes according to https://documentation.help/7-Zip/exit_codes.htm
+	switch (ec)
+	{
+	case SevenZipExitCodes::NoError:
+		return "No error";
+
+	case SevenZipExitCodes::Warning:
+		return "Warning (Non fatal error(s)). \
+		For example, one or more files were locked by some other application, \
+		so they were not compressed.";
+
+	case SevenZipExitCodes::FatalError:
+		return "Fatal error";
+
+	case SevenZipExitCodes::CmdLineError:
+		return "Command line error";
+
+	case SevenZipExitCodes::NotEnoughMemoryError:
+		return "Not enough memory for operation";
+
+	case SevenZipExitCodes::CanceledByUser:
+		return "User stopped the process";
+
+	default: 
+		return "Unknown 7-Zip error";
+	};
+}

daemon/postprocess/Unpack.h

@@ -33,6 +33,7 @@ class UnpackController : public Thread, public ScriptController
 	virtual void Stop();
 	static void StartJob(PostInfo* postInfo);
 	static bool HasCompletedArchiveFiles(NzbInfo* nzbInfo);
+	static const char* DecodeSevenZipExitCode(int ec);
 
 protected:
 	virtual bool ReadLine(char* buf, int bufSize, FILE* stream);
@@ -45,6 +46,16 @@ class UnpackController : public Thread, public ScriptController
 		upSevenZip
 	};
 
+	enum SevenZipExitCodes
+	{
+		NoError = 0,
+		Warning = 1,
+		FatalError = 2,
+		CmdLineError = 7,
+		NotEnoughMemoryError = 8,
+		CanceledByUser = 255,
+	};
+
 	typedef std::vector<CString> FileListBase;
 	class FileList : public FileListBase
 	{

webui/config.js

@@ -3354,7 +3354,7 @@ var ExtensionManager = (new function($)
 			{
 				hideLoadingBanner();
 				render(getAllExtensions());
-				showErrorBanner("Failed to download extensions", error);
+				showErrorBanner("Failed to fetch the list of available extensions", error);
 			}
 		);
 	}

webui/index.html

@@ -718,6 +718,13 @@ <h4 class="alert-heading" id="ExtensionsErrorAlert-title"></h4>
 														<a href="https://github.com/nzbgetcom/nzbget-extensions/blob/main/extensions.json" target="_blank"> list</a>, 
 														it will be removed without the possibility of reinstalling it.
 													</span>
+													<br>
+													<br>
+													<span class="label label-warning">NOTE:</span>
+													<span class="help-option-title">Extension Manager requires 7-Zip to unpack downloaded extensions.
+														If you are having issues with Extension Manager downloads - please check 
+														<a href="#" onclick="Config.scrollToOption(event, this)">SevenZipCmd</a>.
+													</span>
 												</p>
 
 												<br>