Change base path on VS publish

I have a blazorWASM project. While developing, I need index.html to have it's base path set to <base href="/" />, but when I use the built-in publish to file, the output is set to land directly into my PHP project which acts as a host that serves WASM static files, and needs this base path: <base href="/wwwroot/" />.

Is there a way to have them automatically switched so I do not keep forgetting to do so? Alternatively, how do I configure the project so that it will work while I debug it on IIS with the wwwroot base path?

You need to add a build task to your CSPROJ Blazor WASM.

Important note: you need Newtonsoft 13.0.1, System.Text.Json isn't supported.

<UsingTask TaskName="ReplaceBaseHRef" TaskFactory="RoslynCodeTaskFactory" AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.Core.dll">
    <ParameterGroup>
        <InputFilename ParameterType="System.String" Required="true" />
        <AppSettingsfile ParameterType="System.String" Required="true" />
        <BaseHRefAttribute ParameterType="System.String" Required="true" />
    </ParameterGroup>
    <Task>
        <Reference Include="$(NugetPackageRoot)\newtonsoft.json\13.0.1\lib\netstandard2.0\Newtonsoft.Json.dll" />
        <Using Namespace="System" />
        <Using Namespace="System.IO" />
        <Using Namespace="System.Text" />
        <Using Namespace="System.Text.RegularExpressions" />
        <Using Namespace="Newtonsoft.Json" />
        <Using Namespace="Newtonsoft.Json.Linq" />
        <Code Type="Fragment" Language="C#">
            <![CDATA[  
                  var inputFile = File.ReadAllText(InputFilename);                
          var appsetting = File.ReadAllText(AppSettingsfile);

                    JObject appsettings = JObject.Parse(appsetting);

          var baseHRef = appsettings[BaseHRefAttribute].Value<string>();
          if (!string.IsNullOrEmpty(baseHRef)) {
                    Log.LogMessage( MessageImportance.High, baseHRef );

                      var outputFile = InputFilename;
                      var matchExpression = "\\<base\\ href=\\\"(.*)\\\"\\ \\/\\>";
            var newBaseHRef = $"<base href=\"{baseHRef}\" />";
            File.WriteAllText(
              outputFile,
              Regex.Replace(inputFile, matchExpression, newBaseHRef)
              );
          }
        ]]>
        </Code>
    </Task>
</UsingTask>

<Target Name="ReplaceBaseHRef" AfterTargets="Publish">
    <ReplaceBaseHRef InputFilename="$(PublishDir)wwwroot\index.html" AppSettingsfile="$(PublishDir)wwwroot\appsettings.Production.json" BaseHRefAttribute="BaseHRef" />
</Target>

Now take your appsettings.Production.json and add the configuration setting as:

{
  "BaseHRef": "/client/",
  ...
}

now launch the Publish (in folder, IIS or on Azure).

Your index.html will contain <base href="/client/" />.