We missed this one on a previous pass of bringing in most of the cty
stdlib functions.
This will resolve#17625 by allowing conversion from Terraform's
conventional RFC 3339 timestamps into various other formats.
This function is similar to the template_file data source offered by the
template provider, but having it built in to the language makes it more
convenient to use, allowing templates to be rendered from files anywhere
an inline template would normally be allowed:
user_data = templatefile("${path.module}/userdata.tmpl", {
hostname = format("petserver%02d", count.index)
})
Unlike the template_file data source, this function allows values of any
type in its variables map, passing them through verbatim to the template.
Its tighter integration with Terraform also allows it to return better
error messages with source location information from the template itself.
The template_file data source was originally created to work around the
fact that HIL didn't have any support for map values at the time, and
even once map support was added it wasn't very usable. With HCL2
expressions, there's little reason left to use a data source to render
a template; the only remaining reason left to use template_file is to
render a template that is constructed dynamically during the Terraform
run, which is a very rare need.
These implementations are adaptations of the existing implementations in
config/interpolate_funcs.go, updated to work with the cty API.
The set of functions chosen here was motivated mainly by what Terraform's
existing context tests depend on, so we can get the contexts tests back
into good shape before fleshing out the rest of these functions.
Whereas package "configs" deals with the static structure of the
configuration language, this new package "lang" deals with the dynamic
aspects such as expression evaluation.
So far this mainly consists of populating a hcl.EvalContext that contains
the values necessary to evaluate a block or an expression. There is also
special handling here for dynamic block generation using the HCL
"dynblock" extension, which is exposed in the public interface (rather
than hiding it as an implementation detail of EvalBlock) so that the
caller can then extract proper source locations for any result values
using the expanded body.
This also includes the beginnings of a replacement for the function table
handling that currently lives in the old "config" package, but most of
the functions are not yet ported and so this will expand in subsequent
commits.
Martin Atkins