text/template: template function index should permit integer values of float type

[willfaught]

The text/template function index should permit integer values of float type as indexes, since there's no way to convert types in templates themselves.

I hit this particular problem when using unmarshaled JSON as the template data, similar to what's done in the play link below, where an integer in one part refers to an index of a list in another part, but when parsed, the integer is converted to float64.

Note that the function eq is also loose with types.

What did you do?

https://play.golang.org/p/_9K1wu6THk

What did you expect to see?

9

What did you see instead?

template: :1:2: executing "" at <index .a .b>: error calling index: cannot index slice/array with type float64

[bradfitz]

You should probably unmarshal into a concrete type, instead of unmarshalling into interface{}.

I don't think this is a change we want to make. I'm closing this, but I'll let @robpike or @adg reopen if they feel otherwise.

[willfaught]

@bradfitz In my case, the JSON can be anything, hence why it unmarshals into interface{}. I suppose this might be an edge case, but it seems like we already went down this road with eq...

[robpike]

Happy to keep it closed.