When using `output extension` directive with `.gen.cs`, the final file becomes `xxx.gen.gen.cs`

[scottbilas]

Problem

I have this directive in my .tt file:

<#@ output extension=".gen.cs" #>

When using VS or Rider's built-in text templating, this produces an output <filename>.gen.cs. But when using T4.Build, it outputs <filename>.gen.gen.cs.

Solution (my guess)

I don't know how to debug an msbuild task, but looking through the code it appears this is caused by (T4.Build) BuildTemplateGenerator.OutputFile doing a Path.ChangeExtension before (Mono.TextTemplating) TemplateGenerator.SetFileExtension does the same thing.

When using an ordinary extension (.xyz) the double-call doesn't change anything. When using a doubled extension (.xyz.abc) the "sub"-extension gets doubled up, resulting in the <filename>.gen.gen.cs I mentioned above.

My guess on a fix would be, within BuildTemplateGenerator.OutputFile, to only change extension if no output directive is found.

[xavierjohn]

I ran into the same problem
<#@ output extension="g.cs" #>
becomes
g.g.cs

[xavierjohn]

My simple workaround is to add the suffix to tt file

So foo.tt becomes foo.g.tt which will generate foo.g.cs and I can add *.g.cs to .gitignore