This is a first pass of decoding of the main Terraform configuration file
format. It hasn't yet been tested with any real-world configurations, so
it will need to be revised further as we test it more thoroughly.
These types represent the individual elements within configuration, the
modules a configuration is made of, and the configuration (static module
tree) itself.
This method loads a "values file" -- also known as a "tfvars file" -- and
returns the values found inside.
A values file is an HCL file (in either native or JSON syntax) whose
top-level body is treated as a set of arbitrary key/value pairs whose
values may not depend on any variables or functions.
We will load values files through a configs.Parser -- even though values
files are not strictly-speaking part of configuration -- because this
causes them to be registered in our source code cache so that we can
generate source code snippets if we need to report any diagnostics.
configs.Parser is the entry-point for this package, providing functions to
load and parse HCL-based configuration files.
We use the library "afero" to decouple the parser from the physical OS
filesystem, which here allows us to easily use an in-memory filesystem
for testing and will, in future, allow us to read files from more unusual
places, such as configuration embedded in a plan file.
There's a lot of complexity in our existing "config" package that results
from our approach to handling configuration with HCL and HIL. A lot of
that functionality is no longer needed -- or must work in a significantly
different way -- for HCL2.
The new package "configs", which is named following the convention of some
Go standard library packages like "strings", is a re-imagination of some
of the functionality from the "config" package for an HCL2-only world.
The scope of this package will be slightly smaller than "config", since
it only deals with config loading and not with expression evaluation.
Another package "lang" (mentioned in the docstring here but not yet added)
will deal with the more dynamic portions of of configuration handling,
including populating an hcl.EvalContext to evaluate expressions.
Martin Atkins