Commit Graph

8 Commits

Author SHA1 Message Date
Martin Atkins b90fb25321 experiments: a mechanism for opt-in experimental language features
Traditionally we've preferred to release new language features in major
releases only, because we can then use the beta cycle to gather feedback
on the feature and learn about any usability challenges or other
situations we didn't consider during our design in time to make those
changes before inclusion in a stable release.

This "experiments" feature is intended to decouple the feedback cycle for
new features from the major release rhythm, and thus allow us to release
new features in minor releases by first releasing them as experimental for
a minor release or two, adjust for any feedback gathered during that
period, and then finally remove the experiment gate and enable the feature
for everyone.

The intended model here is that anything behind an experiment gate is
subject to breaking changes even in patch releases, and so any module
using these experimental features will be broken by a future Terraform
upgrade.

The behavior implemented here is:

- Recognize a new "experiments" setting in the "terraform" block which
  allows module authors to explicitly opt in to experimental features.

  terraform {
    experiments = [resource_for_each]
  }

- Generate a warning whenever loading a module that has experiments
  enabled, to avoid accidentally depending on experimental features and
  thus risking unexpected breakage on next Terraform upgrade.

- We check the enabled experiments against the configuration at module
  load time, which means that experiments are scoped to a particular
  module. Enabling an experiment in one module does not automatically
  enable it in any other module.

This experiments mechanism is itself an experiment, and so I'd like to
use the resource for_each feature to trial it. Because any configuration
using experiments is subject to breaking changes, we are free to adjust
this experiments feature in future releases as we see fit, but once
for_each is shipped without an experiment gate we'll be blocked from
making significant changes to it until the next major release at least.
2019-12-10 09:27:05 -08:00
Martin Atkins 39e609d5fd vendor: switch to HCL 2.0 in the HCL repository
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.
2019-10-02 15:10:21 -07:00
Martin Atkins 5cf791861f configs: Allow looking up resources by resource addresses.
Throughout the main "terraform" package we identify resources using the
address types, and so this helper is useful to make concise transitions
between the address types and the configuration types.

As part of this, we use the address types to produce the keys used in our
resource maps. This has no visible change in behavior since the prior
implementation produced an equal result, but this change ensures that
ResourceByAddr cannot be broken by hypothetical future changes to the
key serialization.
2018-10-16 18:46:46 -07:00
Martin Atkins 70f1635416 configs: record the source directory for modules
We can only do this when modules are loaded with Parser.LoadConfigDir,
but in practice this is the common case anyway.

This is important to support the path.module and path.root expressions in
configuration.
2018-10-16 18:46:46 -07:00
Martin Atkins c07b0a7806 configs: Re-unify the ManagedResource and DataResource types
Initially the intent here was to tease these apart a little more since
they don't really share much behavior in common in core, but in practice
it'll take a lot of refactoring to tease apart these assumptions in core
right now and so we'll keep these things unified at the configuration
layer in the interests of minimizing disruption at the core layer.

The two types are still kept in separate maps to help reinforce the fact
that they are separate concepts with some behaviors in common, rather than
the same concept.
2018-10-16 18:44:26 -07:00
Martin Atkins 4e5efa498a configs: Parser.LoadConfigDir
This method wraps LoadConfigFile to load all of the .tf and .tf.json files
in a given directory and then bundle them together into a Module object.

This function also deals with the distinction between primary and override
files, first appending together the primary files in lexicographic order
by filename, and then merging in override files in the same order.

The merging behavior is not fully implemented as of this commit, and so
will be expanded in future commits.
2018-02-15 15:56:37 -08:00
Martin Atkins e15ec486bf configs: Parser.LoadConfigFile
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.
2018-02-15 15:56:37 -08:00
Martin Atkins 13fa73c63e configs: stub out main configuration structs
These types represent the individual elements within configuration, the
modules a configuration is made of, and the configuration (static module
tree) itself.
2018-02-15 15:56:37 -08:00