normalize command line arguments

src/cascadia/WindowsTerminal/AppHost.cpp

@@ -73,8 +73,7 @@ bool AppHost::OnF7Pressed()
 }
 
 // Method Description:
-// - Retrieve any commandline args passed on the commandline, and pass them to
-//   the app logic for processing.
+// - Retrieve the command line arguments, and pass them to the app logic for processing.
 // - If the logic determined there's an error while processing that commandline,
 //   display a message box to the user with the text of the error, and exit.
 //    * We display a message box because we're a Win32 application (not a
@@ -87,37 +86,112 @@ bool AppHost::OnF7Pressed()
 // - <none>
 void AppHost::_HandleCommandlineArgs()
 {
-    if (auto commandline{ GetCommandLineW() })
+    const auto args{ _GetArgs() };
+    if (!args.empty())
     {
-        int argc = 0;
+        const auto result = _logic.SetStartupCommandline({ args });
+        const auto message = _logic.EarlyExitMessage();
+        if (!message.empty())
+        {
+            const auto displayHelp = result == 0;
+            const auto messageTitle = displayHelp ? IDS_HELP_DIALOG_TITLE : IDS_ERROR_DIALOG_TITLE;
+            const auto messageIcon = displayHelp ? MB_ICONWARNING : MB_ICONERROR;
+            // TODO:GH#4134: polish this dialog more, to make the text more
+            // like msiexec /?
+            MessageBoxW(nullptr,
+                        message.data(),
+                        GetStringResource(messageTitle).data(),
+                        MB_OK | messageIcon);
+
+            ExitProcess(result);
+        }
+    }
+}
+
+// Method Description:
+// - Retrieve the command line.
+// - Use our own algorithm to tokenize it because `CommandLineToArgvW` treats \"
+//   as an escape sequence to preserve the quotation mark (GH#4571)
+//   Instead treat a pair of consecutive quotation marks as a single quotation mark.
+// - Populate the arguments as vector of hstrings.
+// Arguments:
+// - <none>
+// Return Value:
+// - Program arguments as vector of hstrings. If the function fails it returns an empty vector.
+std::vector<winrt::hstring> AppHost::_GetArgs() const noexcept
+{
+    try
+    {
+        std::vector<winrt::hstring> args{};
+        // get the command line
+        const wchar_t* const cmdLnPtr{ GetCommandLineW() };
+        if (!cmdLnPtr)
+        {
+            return {};
+        }
 
-        // Get the argv, and turn them into a hstring array to pass to the app.
-        wil::unique_any<LPWSTR*, decltype(&::LocalFree), ::LocalFree> argv{ CommandLineToArgvW(commandline, &argc) };
-        if (argv)
+        std::wstring cmdLn{ cmdLnPtr };
+        auto cmdLnEnd{ cmdLn.end() }; // end of still valid content in the command line
+        auto iter{ cmdLn.begin() }; // iterator pointing to the current position in the command line
+        auto argBegin{ iter }; // iterator pointing to the begin of an argument
+        auto firstQuote{ cmdLnEnd }; // iterator pointing to the first quotation mark of a pair of quotation marks
+        auto quoted{ false }; // indicates whether a substring is quoted
+        auto within{ false }; // indicates whether the current character is inside of an argument
+
+        args.reserve(gsl::narrow_cast<size_t>(64U)); // pre-allocate some space for the string handles
+        while (iter < cmdLnEnd)
         {
-            std::vector<winrt::hstring> args;
-            for (auto& elem : wil::make_range(argv.get(), argc))
+            auto increment{ true }; // used to avoid iterator incrementation if a quotation mark has been removed
+            switch (*iter)
             {
-                args.emplace_back(elem);
+            case L' ': // space and tab are the usual separators for arguments
+            case L'\t':
+                if (!quoted && within)
+                {
+                    within = false;
+                    args.emplace_back(std::wstring{ argBegin, iter });
+                }
+                break;
+
+            case L'"': // quotation marks need special handling
+                quoted = !quoted;
+                if (firstQuote == iter) // treat "" as a single "
+                {
+                    firstQuote = cmdLnEnd;
+                }
+                else
+                {
+                    firstQuote = iter;
+                    std::move(iter + 1, cmdLnEnd, iter); // move the rest of the command line to the left to overwrite the quote
+                    --cmdLnEnd; // the string isn't shorter but its valid content is, we can't just resize without potentially invalidate iterators
+                    increment = false; // indicate that iter shall not be incremented because it already points to a new character
+                }
+                [[fallthrough]];
+            default: // any other character (including quotation mark)
+                if (!within)
+                {
+                    within = true;
+                    argBegin = iter;
+                }
+                break;
             }
 
-            const auto result = _logic.SetStartupCommandline({ args });
-            const auto message = _logic.EarlyExitMessage();
-            if (!message.empty())
+            if (increment)
             {
-                const auto displayHelp = result == 0;
-                const auto messageTitle = displayHelp ? IDS_HELP_DIALOG_TITLE : IDS_ERROR_DIALOG_TITLE;
-                const auto messageIcon = displayHelp ? MB_ICONWARNING : MB_ICONERROR;
-                // TODO:GH#4134: polish this dialog more, to make the text more
-                // like msiexec /?
-                MessageBoxW(nullptr,
-                            message.data(),
-                            GetStringResource(messageTitle).data(),
-                            MB_OK | messageIcon);
-
-                ExitProcess(result);
+                ++iter;
             }
         }
+
+        if (within)
+        {
+            args.emplace_back(std::wstring{ argBegin, iter });
+        }
+
+        return args;
+    }
+    catch (...)
+    {
+        return {};
     }
 }
 

src/cascadia/WindowsTerminal/AppHost.h

@@ -27,6 +27,7 @@ class AppHost
     winrt::TerminalApp::AppLogic _logic;
 
     void _HandleCommandlineArgs();
+    std::vector<winrt::hstring> _GetArgs() const noexcept;
 
     void _HandleCreateWindow(const HWND hwnd, RECT proposedRect, winrt::TerminalApp::LaunchMode& launchMode);
     void _UpdateTitleBarContent(const winrt::Windows::Foundation::IInspectable& sender,