Adding package references via post action doesn't work

I’m trying to dynamically add a new package reference to a solution template based on a symbol set previously through parameters in the post actions of my template, like this (package references changed for privacy):

{
   ...
    "symbols": {
        "hosting": {
            "type": "parameter",
            "datatype": "choice",
            "description": "Choose between HttpSys and Kestrel for ASP.NET Core hosting",
            "choices": [
                {
                    "choice": "httpsys",
                    "description": "HttpSys hosting"
                },
                {
                    "choice": "kestrel",
                    "description": "Kestrel hosting"
                }
            ],
            "defaultValue": "httpsys"
        }
        // other params go here...
    },
    "postActions": [
        {
            "condition": "(hosting == 'httpsys')",
            "description": "Adding reference to HttpSys",
            "manualInstructions": [
                { "text": "Manually add the reference to your project file" }
            ],
            "actionId": "B17581D1-C5C9-4489-8F0A-004BE667B814",
            "continueOnError": true,
            "args": {
                "referenceType": "package",
                "reference": "Microsoft.AspNetCore.Server.HttpSys",
                "version": "2.2.6",
                "targetFiles": "MyProject/MyProject.csproj"
            }
        },
        {
            "condition": "(hosting == 'kestrel')",
            "description": "Adding reference to Kestrel",
            "manualInstructions": [
                { "text": "Manually add the reference to your project file" }
            ],
            "actionId": "B17581D1-C5C9-4489-8F0A-004BE667B814",
            "continueOnError": true,
            "args": {
                "referenceType": "package",
                "reference": "Microsoft.AspNetCore.Server.Kestrel",
                "version": "2.2.0",
                "targetFiles": "MyProject/MyProject.csproj"
            }
        }
    ]
}

For adding post actions, I’ve been following the docs for post action registries at https://github.com/dotnet/templating/wiki/Post-Action-Registry#add-a-reference-to-a-project-file.

Running dotnet new mytemplate -n test123 unfortunately results in a very short error message without an explanation as to why it fails:

PS C:\Users\user\repos> dotnet new mytemplate -n test123
The template "App template" was created successfully.

Processing post-creation actions...
Post action failed.
Manual instructions: Manually add the reference to your project file

I’ve verified that the package references are compatible by manually running dotnet add package Microsoft.AspNetCore.Server.HttpSys --version 2.2.6, which adds a reference to the newly generated .csproj file just fine. My colleagues have tested the template as well, resulting in the same error message. I’ve already tried working around this using a powershell script, but it would be way easier to use post actions for this purpose.

dotnet --version: 6.0.301 Platform: Windows

[vlada-shubina]

We may consider servicing the following for 6.0.4xx:

• https://github.com/dotnet/templating/pull/4869
• https://github.com/dotnet/templating/pull/4922
• https://github.com/dotnet/templating/pull/4948

I’ll keep posted on decision made.

[GangWang01]

Update more detail on the investigation above.

For dotnet 6.0.301 and above, it needs ./ prefix with relative path of targetFiles to get adding package reference post action work. But the command like dotnet new mytemplate -n test123 doesn’t work because of -n test123. It renames project file when instantiating template. While just as the note of https://github.com/dotnet/templating/wiki/Post-Action-Registry#add-a-reference-to-a-project-file the file name change is ignored when using targetFiles.

Commit https://github.com/dotnet/templating/commit/b7dc29745861400991ca519f85bfd8a9eee43fd4 in main branch resolved the problem. targetFiles can know the file name change when instantiating template.