Blazor based templates not adhering to modifiers

[isaacrlevin]

I am updating the Blazor templates for 3.0 and I am running across an issue when I dotnet new the new template I created. I created a new options called hosted that will toggle whether or not the Blazor Web Assembly project should use an ASP.NET Core backend.

dotnetcli.host.json

      "Hosted": {
        "longName": "hosted"
      }

Symbol

    "Hosted": {
      "type": "parameter",
      "datatype": "bool",
      "defaultValue": "false",
      "description": "Whether to use ASP.NET Core Hosted Backend."
    }

Modifiers

           "condition": "(!Hosted)",
          "exclude": [
            "BlazorHosted-CSharp/Server/**",
            "BlazorHosted-CSharp/Shared/**"
          ]
        },
        {
          "condition": "(Hosted)",
          "exclude": [
            "BlazorHosted-CSharp/Client/wwwroot/sample-data/**"
          ]
        }

So basically if hosted is false, I should only have one project generated. This is not working, though I assume I may be doing something wrong. I talked with @seancpeters and he mentioned it may be an issue, so I am tracking here.

[seancpeters]

I'm not dug too deep into this, but the issue appears to be that files that are renamed are not properly handled by source modifiers.

[danroth27]

@vijayrkn FYI - looks like this is blocking our template updates.

[isaacrlevin]

@danroth27 @vijayrkn is there an ETA for when this work can start (or someone wants to show me where to look)?

[seancpeters]

As a workaround, in the template source, if you rename the directories that are conditionally excluded, in a way that causes them to not be renamed during template processing, things should work as expected. For example, call the directories "Hosted-CSharp." instead of "BlazorHosted-CSharp."

[seancpeters]

@phenning - The fix for this issue will most like begin in one or both of these places, they're probably the most useful places to start looking:
https://github.com/dotnet/templating/blob/stabilize/src/Microsoft.TemplateEngine.Core/Util/Orchestrator.cs
...in the method RunInternal()

https://github.com/dotnet/templating/blob/stabilize/src/Microsoft.TemplateEngine.Orchestrator.RunnableProjects/SimpleConfigModel.cs
… in the property IRunnableProjectConfig.Sources

[AR-May]

After running some templates to reproduce the issue, it seems to me that excluding is performed before renaming, so the template engine does the exclude modifier with old, non-renamed files.

Excluding and renaming are both modifiers and it seems reasonable that we have a certain order for modifiers to be performed. If we change the current behavior and allow either renamed files to be excluded also (exclude -> rename -> exclude), or just change the order of operations (rename -> exclude), this might be a breaking change for template authors.

Fortunately, there is a workaround for the problem, as stated above. After a discussion with @KathleenDollard, we decided not to fix this, so I am closing the issue. However, if I understood the problem wrong or the workaround does not work and you are still blocked, please do not hesitate to reopen this and continue the discussion.