Launch elevated instances via shell:AppFolder (#14637)

This uses `shell:AppsFolder` to launch elevated instances of the app via
`ShellExecuteEx` and `runas` in elevate-shim.exe. The app to launch is
discovered via the `GetCurrentApplicationUserModelId` API.

e.g. `shell:AppsFolder\WindowsTerminalDev_8wekyb3d8bbwe!App`

This will fallback to launching `WindowsTerminal.exe` if it fails to
discover the app user model id to launch.

This also fixes a bug in elevate-shim where the first argument of
WinMain was lost (e.g. `new-tab`).

Curiously, `AppLogic::RunAsUwp()` is never called and
`AppLogic::IsUwp()` is always false when running debug builds locally
(e.g. WindowsTerminalDev). It's not clear if this is an artifact of
development packages or something else.

## Validation Steps Performed

Various manual debug/execution scenarios.

Verified the fallback path by running the unbundled app by extracting
the `CascadiaPackage_0.0.1.0_x64.msix` from the 'drop' build artifact.

Fixes #14501

(cherry picked from commit eab1c23)
Service-Card-Id: 87690177
Service-Version: 1.16

src/cascadia/ElevateShim/elevate-shim.cpp

@@ -9,7 +9,10 @@
 #include <wil/stl.h>
 #include <wil/resource.h>
 #include <wil/win32_helpers.h>
+#include <gsl/gsl_util>
+#include <gsl/pointers>
 #include <shellapi.h>
+#include <appmodel.h>
 
 // BODGY
 //
@@ -25,18 +28,68 @@
 // process can successfully elevate.
 
 #pragma warning(suppress : 26461) // we can't change the signature of wWinMain
-int __stdcall wWinMain(HINSTANCE, HINSTANCE, LPWSTR pCmdLine, int)
+int __stdcall wWinMain(HINSTANCE, HINSTANCE, LPWSTR, int)
 {
-    // All of the args passed to us (something like `new-tab -p {guid}`) are in
-    // pCmdLine
+    // This will invoke an elevated terminal in two possible ways. See GH#14501
+    // In both scenarios, it passes the entire cmdline as-is to the new process.
+    //
+    // #1 discover and invoke the app using the GetCurrentApplicationUserModelId
+    // api using shell:AppsFolder\package!appid
+    //    cmd:    shell:AppsFolder\WindowsTerminalDev_8wekyb3d8bbwe!App
+    //    params: new-tab -p {guid}
+    //
+    // #2 find and execute WindowsTerminal.exe
+    //    cmd:    {same path as this binary}\WindowsTerminal.exe
+    //    params: new-tab -p {guid}
 
-    // Get the path to WindowsTerminal.exe, which should live next to us.
-    std::filesystem::path module{ wil::GetModuleFileNameW<std::wstring>(nullptr) };
-    // Swap elevate-shim.exe for WindowsTerminal.exe
-    module.replace_filename(L"WindowsTerminal.exe");
+    // see if we're a store app we can invoke with shell:AppsFolder
+    std::wstring appUserModelId;
+    const auto result = wil::AdaptFixedSizeToAllocatedResult<std::wstring, APPLICATION_USER_MODEL_ID_MAX_LENGTH>(
+        appUserModelId, [&](PWSTR value, size_t valueLength, gsl::not_null<size_t*> valueLengthNeededWithNull) noexcept -> HRESULT {
+            UINT32 length = gsl::narrow_cast<UINT32>(valueLength);
+            const LONG rc = GetCurrentApplicationUserModelId(&length, value);
+            switch (rc)
+            {
+            case ERROR_SUCCESS:
+                *valueLengthNeededWithNull = length;
+                return S_OK;
+
+            case ERROR_INSUFFICIENT_BUFFER:
+                *valueLengthNeededWithNull = length;
+                return S_FALSE; // trigger allocation loop
+
+            case APPMODEL_ERROR_NO_APPLICATION:
+                return E_FAIL; // we are not running as a store app
+
+            default:
+                return E_UNEXPECTED;
+            }
+        });
+    LOG_IF_FAILED(result);
+
+    std::wstring cmd = {};
+    if (result == S_OK && appUserModelId.length() > 0)
+    {
+        // scenario #1
+        cmd = L"shell:AppsFolder\\" + appUserModelId;
+    }
+    else
+    {
+        // scenario #2
+        // Get the path to WindowsTerminal.exe, which should live next to us.
+        std::filesystem::path module{
+            wil::GetModuleFileNameW<std::wstring>(nullptr)
+        };
+        // Swap elevate-shim.exe for WindowsTerminal.exe
+        module.replace_filename(L"WindowsTerminal.exe");
+        cmd = module;
+    }
 
     // Go!
 
+    // The cmdline argument passed to WinMain is stripping the first argument.
+    // Using GetCommandLine() instead for lParameters
+
     // disable warnings from SHELLEXECUTEINFOW struct. We can't fix that.
 #pragma warning(push)
 #pragma warning(disable : 26476) // Macro uses naked union over variant.
@@ -46,8 +99,10 @@ int __stdcall wWinMain(HINSTANCE, HINSTANCE, LPWSTR pCmdLine, int)
     seInfo.cbSize = sizeof(seInfo);
     seInfo.fMask = SEE_MASK_DEFAULT;
     seInfo.lpVerb = L"runas"; // This asks the shell to elevate the process
-    seInfo.lpFile = module.c_str(); // This is `...\WindowsTerminal.exe`
-    seInfo.lpParameters = pCmdLine; // This is `new-tab -p {guid}`
+    seInfo.lpFile = cmd.c_str(); // This is `shell:AppsFolder\...` or `...\WindowsTerminal.exe`
+    seInfo.lpParameters = GetCommandLine(); // This is `new-tab -p {guid}`
     seInfo.nShow = SW_SHOWNORMAL;
     LOG_IF_WIN32_BOOL_FALSE(ShellExecuteExW(&seInfo));
+
+    return 0;
 }