Package tstruct provides template FuncMap helpers to construct struct literals within a Go template.

In your Go code:

type T struct {
    S string
    N int
    M map[string]int
    L []float64
}

m := template.FuncMap{ /* your func map here */ }
err := tstruct.AddFuncMap[T](m)
// handle err

This will register FuncMap functions called T, S, N, M, and L, for the struct name and each of its fields. You can use them to construct and populate a T from a template:

{{ template "template-that-renders-T" T
  (S "a string")
  (L 1.0 2.0)
  (M "one map entry" 1)
  (M "another map entry" 2)
  (M "x" 3 "y" 4)
  (N 42)
  (L 4.0)
}}

And voila: Your template will be called with a struct equal to:

T{
    S: "a string",
    N: 42,
    M: map[string]int{"one map entry": 1, "another map entry": 2, "x": 3, "y": 4},
    L: []float64{1.0, 2.0, 4.0},
}

Note that order is irrelevant, except for slice appends.

As a special case (matching package flag), you may omit the argument true when setting a bool field to true: (Enabled) is equivalent to (Enabled true).

If you have multiple struct types whose fields share a name, the field setters will Just Work, despite having a single name. However, no two struct types may share a name, nor can a struct type and a field share a name.

To request that tstruct ignore a struct field, add the struct tag tstruct:"-" to it.

To require that a value for struct field be explicitly provided, add the struct tag tstruct:"+" to it.

If you need to construct an unusual type from a template, there's a magic method: TStructSet. To use it, declare a type that has that method on a pointer receiver. It can accept any number of args, which will be passed directly from the template args. In the method, set the value according to the args.

Example:

type Repeat string

func (x *Repeat) TStructSet(s string, count int) {
	*x = Repeat(strings.Repeat(s, count))
}

type U struct {
    S Repeat
}

In your template:

{{ $lab := U (S "hi " 15) }}

That creates a U, and populates its S field by calling (*Repeat).TStructSet with arguments "hi " and 15.

The conflict with the field named S in type T is handled automatically.

---

If this is not what you wanted, you might check out https://pkg.go.dev/rsc.io/tmplfunc.

If this is almost what you wanted, but not quite, tell me about it. :)