The current way to refer to a managed resource is to use its resource type
name as a top-level symbol in the reference. This is convenient and makes
sense given that managed resources are the primary kind of object in
Terraform.
However, it does mean that an externally-extensible namespace (the set
of all possible resource type names) overlaps with a reserved word
namespace (the special prefixes like "path", "var", etc), and thus
introducing any new reserved prefix in future risks masking an existing
resource type so it can't be used anymore.
We only intend to introduce new reserved symbols as part of future
language editions that each module can opt into separately, and when doing
so we will always research to try to choose a name that doesn't overlap
with commonly-used providers, but not all providers are visible to us and
so there is always a small chance that the name we choose will already be
in use by a third-party provider.
In preparation for that event, this introduces an alternative way to refer
to managed resources that mimics the reference style used for data
resources: resource.type.name . When using this form, the second portion
is _always_ a resource type name and never a reserved word.
There is currently no need to use this because all of the already-reserved
symbol names are effectively blocked from use by existing Terraform
versions that lack this escape hatch. Therefore there's no explicit
documentation about it yet.
The intended use for this is that a module upgrade tool for a future
language edition would detect references to resource types that have now
become reserved words and add the "resource." prefix to keep that
functionality working. Existing modules that aren't opted in to the new
language edition would keep working without that prefix, thus keeping to
compatibility promises.
In order to be able to use module values, and handle operations like
possibly invalid module indexes in conditional statements, whole modules
must always be returned during evaluation.
self references do not need to be added to `managedResource`, and in
fact that could cause issues later if self is allowed in contexts other
than managed resources.
Coalesce 2 cases in the Referenceable switch, be take the
ContainingResource address of an instance beforehand.
Previously we were using the experimental HCL 2 repository, but now we'll
shift over to the v2 import path within the main HCL repository as part of
actually releasing HCL 2.0 as stable.
This is a mechanical search/replace to the new import paths. It also
switches to the v2.0.0 release of HCL, which includes some new code that
Terraform didn't previously have but should not change any behavior that
matters for Terraform's purposes.
For the moment the experimental HCL2 repository is still an indirect
dependency via terraform-config-inspect, so it remains in our go.sum and
vendor directories for the moment. Because terraform-config-inspect uses
a much smaller subset of the HCL2 functionality, this does still manage
to prune the vendor directory a little. A subsequent release of
terraform-config-inspect should allow us to completely remove that old
repository in a future commit.
Continue only evaluating resource at a whole and push the indexing of
the resource down into the expression evaluation.
The exception here is that `self` must be an instance which must be
extracted from the resource. We now also add the entire resource to the
context, which was previously only partially populated with the self
referenced instance.
Previously it was calling directly to hcldec.Variables, and thus missing
the special fixups we do inside ReferencesInBlock to deal with
Terraform-specific concerns such as our attribute-as-blocks preprocessing.
The "config" package is no longer used and will be removed as part
of the 0.12 release cleanup. Since configschema is part of the
"new world" of configuration modelling, it makes more sense for
it to live as a subdirectory of the newer "configs" package.
Due to how deeply the configuration types go into Terraform Core, there
isn't a great way to switch out to HCL2 gradually. As a consequence, this
huge commit gets us from the old state to a _compilable_ new state, but
does not yet attempt to fix any tests and has a number of known missing
parts and bugs. We will continue to iterate on this in forthcoming
commits, heading back towards passing tests and making Terraform
fully-functional again.
The three main goals here are:
- Use the configuration models from the "configs" package instead of the
older models in the "config" package, which is now deprecated and
preserved only to help us write our migration tool.
- Do expression inspection and evaluation using the functionality of the
new "lang" package, instead of the Interpolator type and related
functionality in the main "terraform" package.
- Represent addresses of various objects using types in the addrs package,
rather than hand-constructed strings. This is not critical to support
the above, but was a big help during the implementation of these other
points since it made it much more explicit what kind of address is
expected in each context.
Since our new packages are built to accommodate some future planned
features that are not yet implemented (e.g. the "for_each" argument on
resources, "count"/"for_each" on modules), and since there's still a fair
amount of functionality still using old-style APIs, there is a moderate
amount of shimming here to connect new assumptions with old, hopefully in
a way that makes it easier to find and eliminate these shims later.
I apologize in advance to the person who inevitably just found this huge
commit while spelunking through the commit history.
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