@runner-mei I assume that this is a feature request to be able to chain methods via pipelines, is that correct?

Have you considered doing something like {{with $x := text_field "username" | call $x.Render }}?

Also note that currently the parser is the one that rejects undefined functions. If this feature were to get implemented, we'd have to drop that check entirely, as it would be impossible to tell if a function is defined or not at parse time.

I personally think this is not a good idea. It seems like you can already accomplish the task with the current template language, and we don't want to complicate the language unless strictly necessary.

/cc @robpike

@mvdan yes, this is a feature request to be able to chain methods via pipelines.

no, We didn't give up that check entirely，result of function text_field is *TextField (not interface{}), We can try to obtain the return value type and check it.

I would prefer not to do this. The grammar is subtle enough as is, the execution logic even more so, and it is easy, as shown above, to achieve the desired result with the existing template language.

@robpike Now the grammar is insufficient, it is cumbersome。

It's a bug? the following statements are incorrect, they run ok and don't have any output

{{with $x := text_field "username" | call $x.SetValue .value | call $x.Render }}{{end}}
{{with $x := text_field "username" | call $x.SetValue .value | call $x.Render }}{{$x}}{{end}}
{{with $x := text_field "username"}}{{call $x.SetValue .value}}{{call $x.Render }}{{end}}
{{with $x := text_field "username" }} {{ $x.SetValue .value }} {{ $x.Render}} {{end}}
{{with $x := text_field "username" |  $x.SetValue .value |  $x.Render }}{{end}}
{{with $x := text_field "username" |  $x.SetValue .value |  $x.Render }}{{$x}}{{end}}
{{with text_field "username"}}{{ $.SetValue .value |  $.Render }}{{end}}
{{with text_field "username"}}{{call  $.SetValue .value  }}{{ call $.Render }}{{end}}

only the following statements are correct

{{with $x := text_field "username" }} {{ $x.Render}} {{end}}  // but cannot invoke SetValue  in the with block

or add '@' prefix

{{text_field "username" |@SetValue .value |@Render }}