WiX安装前卸载旧NSIS应用：安装目录为空问题排查

背景 #

我们计划用WiX制作的MSI替换旧NSIS安装包，实现新版本安装时自动静默卸载旧版本，当前WiX配置如下：

<!-- Custom action to uninstall old app if it's already installed -->
<!-- 1.Check if old app is installed by checking if it exists in the registry -->
<Property Id="OLDAPPUNINSTALLERCOMMAND">
    <RegistrySearch Id="OldAppUninstallerRegistrySearch" Type="raw" Root="HKLM"
    Key="SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\12345"
    Name="QuietUninstallString" Win64="yes"/>
</Property>
<!-- 2. Create a custom action to uninstall old app -->
<SetProperty Id="RemoveOldApp" Value="[OLDAPPUNINSTALLERCOMMAND]"
            Sequence="execute" Before="RemoveOldApp" />
<CustomAction Id="RemoveOldApp" BinaryKey="WixCA" DllEntry="WixQuietExec64" Execute="deferred" Impersonate="no" Return="check" />
<!-- 3. Schedule the custom action after installer initialisation, if old app was found -->
<InstallExecuteSequence>
    <Custom Action="RemoveOldApp" After="InstallInitialize">RemoveOldApp</Custom>
</InstallExecuteSequence>

遇到的问题 #

• 无旧应用时，新应用安装完全正常
• 存在旧应用时，卸载完成后新应用虽出现在添加/删除程序（ARP）中，但安装目录为空，仅手动修改安装后文件才会显示内容
• NSIS卸载未阻塞WiX流程：NSIS卸载弹窗与安装结束弹窗同时出现，WiX提前完成安装流程，而NSIS卸载仍在后台运行
• 根因：NSIS卸载器会将自身复制到临时目录，携带参数_?=ABC执行后立即返回原进程，导致WiX误以为卸载已完成，提前继续安装步骤，引发文件写入冲突

解决方案 #

针对NSIS卸载的异步返回机制，需让WiX等待卸载进程（包括其临时子进程）完全结束后再继续安装，以下是两种可行方案：

方案1：使用批处理脚本等待进程结束 #

1. 创建批处理脚本WaitForNSISUninstall.cmd，内容如下：

@echo off
:: 执行NSIS卸载命令
%~1
:: 等待NSIS相关进程结束（替换为实际旧卸载器的进程名）
:WAIT_LOOP
tasklist | find /i "nsis.exe" >nul
if errorlevel 1 goto UNINSTALL_DONE
timeout /t 1 /nobreak >nul
goto WAIT_LOOP
:UNINSTALL_DONE

注意：若旧NSIS卸载器的进程名不是nsis.exe，需替换为实际进程名。

2. 修改WiX配置，调用该批处理执行卸载：

<!-- 1. 检查旧应用卸载命令 -->
<Property Id="OLDAPPUNINSTALLERCOMMAND">
    <RegistrySearch Id="OldAppUninstallerRegistrySearch" Type="raw" Root="HKLM"
    Key="SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\12345"
    Name="QuietUninstallString" Win64="yes"/>
</Property>

<!-- 2. 设置自定义动作参数，调用批处理脚本 -->
<SetProperty Id="RemoveOldApp" Value="&quot;[TempFolder]WaitForNSISUninstall.cmd&quot; &quot;[OLDAPPUNINSTALLERCOMMAND]&quot;"
               Sequence="execute" Before="RemoveOldApp" />

<!-- 3. 自定义动作执行批处理 -->
<CustomAction Id="RemoveOldApp" BinaryKey="WixCA" DllEntry="WixQuietExec64" Execute="deferred" Impersonate="no" Return="check" />

<!-- 4. 调度自定义动作：仅当旧应用存在且是首次安装时执行 -->
<InstallExecuteSequence>
    <Custom Action="RemoveOldApp" After="InstallInitialize">(OLDAPPUNINSTALLERCOMMAND AND NOT Installed)</Custom>
</InstallExecuteSequence>

需将WaitForNSISUninstall.cmd添加到WiX的文件组件中，确保安装时复制到临时目录或安装目录。

方案2：使用C#自定义动作等待进程 #

编写C#自定义动作，直接调用卸载命令并等待所有相关进程结束：

using System;
using System.Diagnostics;
using Microsoft.Deployment.WindowsInstaller;

public class CustomActions
{
    [CustomAction]
    public static ActionResult WaitForNSISUninstall(Session session)
    {
        string uninstallCmd = session["OLDAPPUNINSTALLERCOMMAND"];
        if (string.IsNullOrWhiteSpace(uninstallCmd))
        {
            return ActionResult.Success;
        }

        // 拆分命令行和参数
        int argStartIndex = uninstallCmd.IndexOf(' ');
        string exePath = argStartIndex > 0 ? uninstallCmd.Substring(0, argStartIndex) : uninstallCmd;
        string arguments = argStartIndex > 0 ? uninstallCmd.Substring(argStartIndex + 1) : string.Empty;

        // 启动卸载进程
        using (Process uninstallProcess = Process.Start(new ProcessStartInfo(exePath, arguments)
        {
            CreateNoWindow = true,
            WindowStyle = ProcessWindowStyle.Hidden,
            UseShellExecute = false
        }))
        {
            uninstallProcess.WaitForExit();
        }

        // 等待可能存在的NSIS临时子进程
        foreach (Process childProcess in Process.GetProcessesByName("nsis"))
        {
            childProcess.WaitForExit();
        }

        return ActionResult.Success;
    }
}

编译该自定义动作后，在WiX中引用并替换原有的WixQuietExec64动作：

<Binary Id="CustomActions.dll" SourceFile="path/to/CustomActions.dll" />
<CustomAction Id="RemoveOldApp" BinaryKey="CustomActions.dll" DllEntry="WaitForNSISUninstall" Execute="deferred" Impersonate="no" Return="check" />

<InstallExecuteSequence>
    <Custom Action="RemoveOldApp" After="InstallInitialize">(OLDAPPUNINSTALLERCOMMAND AND NOT Installed)</Custom>
</InstallExecuteSequence>

内容的提问来源于stack exchange，提问作者Rajveer