Bug 39711964: WinAppSDK: DeploymentManager doesn't handle ERROR_INSUFFICIENT_BUFFER (#2548)

* Bug 39711964: WinAppSDK: DeploymentManager doesn't handle ERROR_INSUFFICIENT_BUFFER

* Forgot to remove the original (bugged) line

* Fix Breakaway support

* Remove PROC_THREAD_ATTRIBUTE_HANDLE_LIST. The code was derived from AppLifecycleAgent but UpdateProcThread(PROC_THREAD_ATTRIBUTE_HANDLE_LIST, size=0, list=null) error'd. We don't actually need a list of handles (unlike AppLifecycleAgent was passing a list) so we can remove this attribute

dev/Deployment/DeploymentManager.cpp

@@ -310,6 +310,7 @@ namespace winrt::Microsoft::Windows::ApplicationModel::WindowsAppRuntime::implem
         return modulePath.parent_path() / c_deploymentAgentFilename;
     }
 
+    /// @warning This function is ONLY for processes with package identity. It's the caller's responsibility to ensure this.
     HRESULT DeploymentManager::AddPackageInBreakAwayProcess(const std::filesystem::path& packagePath, const bool forceDeployment) try
     {
         auto exePath{ GenerateDeploymentAgentPath() };
@@ -321,28 +322,21 @@ namespace winrt::Microsoft::Windows::ApplicationModel::WindowsAppRuntime::implem
         SIZE_T attributeListSize{};
         auto attributeCount{ 1 };
 
-        if (AppModel::Identity::IsPackagedProcess())
-        {
-            // Packaged scenarios have an additional attribute.
-            attributeCount++;
-        }
-
-        THROW_IF_WIN32_BOOL_FALSE(InitializeProcThreadAttributeList(nullptr, attributeCount, 0, &attributeListSize));
-        PPROC_THREAD_ATTRIBUTE_LIST attributeList = reinterpret_cast<PPROC_THREAD_ATTRIBUTE_LIST>(new BYTE[attributeListSize]);
+        // attributeCount is always >0 so we need to allocate a buffer. Call InitializeProcThreadAttributeList()
+        // to determine the size needed so we always expect ERROR_INSUFFICIENT_BUFFER.
+        THROW_HR_IF(E_UNEXPECTED, !!InitializeProcThreadAttributeList(nullptr, attributeCount, 0, &attributeListSize));
+        const auto lastError{ GetLastError() };
+        THROW_HR_IF(HRESULT_FROM_WIN32(lastError), lastError != ERROR_INSUFFICIENT_BUFFER);
+        wistd::unique_ptr<BYTE[]> attributeListBuffer{ new BYTE[attributeListSize] };
+        auto attributeList{ reinterpret_cast<PPROC_THREAD_ATTRIBUTE_LIST>(attributeListBuffer.get()) };
         THROW_IF_WIN32_BOOL_FALSE(InitializeProcThreadAttributeList(attributeList, attributeCount, 0, &attributeListSize));
         auto freeAttributeList{ wil::scope_exit([&] { DeleteProcThreadAttributeList(attributeList); }) };
 
-        // Launch the deployment agent
-        THROW_IF_WIN32_BOOL_FALSE(UpdateProcThreadAttribute(attributeList, 0, PROC_THREAD_ATTRIBUTE_HANDLE_LIST, nullptr, 0, nullptr, nullptr));
-
-        if (AppModel::Identity::IsPackagedProcess())
-        {
-            // Desktop Bridge applications by default have their child processes break away from the parent process.  In order to recreate the calling process'
-            // environment correctly, this code must prevent child breakaway semantics when calling the agent. Additionally the agent must do the same when
-            // restarting the caller.
-            DWORD policy{ PROCESS_CREATION_DESKTOP_APP_BREAKAWAY_OVERRIDE };
-            THROW_IF_WIN32_BOOL_FALSE(UpdateProcThreadAttribute(attributeList, 0, PROC_THREAD_ATTRIBUTE_DESKTOP_APP_POLICY, &policy, sizeof(policy), nullptr, nullptr));
-        }
+        // Desktop Bridge applications by default have their child processes break away from the parent process.
+        // In order to recreate the calling process' environment correctly, we must prevent child breakaway semantics
+        // when calling the agent. Additionally the agent must do the same when restarting the caller.
+        DWORD policy{ PROCESS_CREATION_DESKTOP_APP_BREAKAWAY_OVERRIDE };
+        THROW_IF_WIN32_BOOL_FALSE(UpdateProcThreadAttribute(attributeList, 0, PROC_THREAD_ATTRIBUTE_DESKTOP_APP_POLICY, &policy, sizeof(policy), nullptr, nullptr));
 
         STARTUPINFOEX info{};
         info.StartupInfo.cb = sizeof(info);