This allows precondition and postcondition checks to be declared for
resources and output values as long as the preconditions_postconditions
experiment is enabled.
Terraform Core doesn't currently know anything about these features, so
as of this commit declaring them does nothing at all.
Based on feedback during earlier alpha releases, we've decided to move
forward with the current design for the first phase of config-driven
refactoring.
Therefore here we've marked the experiment as concluded with no changes
to the most recent incarnation of the functionality. The other changes
here are all just updating test fixtures to no longer declare that they
are using experimental features.
The current behavior of module input variables is to allow users to
override a default by assigning `null`, which works contrary to the
behavior of resource attributes, and prevents explicitly accepting a
default when the input must be defined in the configuration.
Add a new variable attribute called `nullable` will allow explicitly
defining when a variable can be set to null or not. The current default
behavior is that of `nullable=true`.
Setting `nullable=false` in a variable block indicates that the variable
value can never be null. This either requires a non-null input value, or
a non-null default value. In the case of the latter, we also opt-in to
the new behavior of a `null` input value taking the default rather than
overriding it.
In a future language edition where we make `nullable=false` the default,
setting `nullable=true` will allow the legacy behavior of `null`
overriding a default value. The only future configuration in which this
would be required even if the legacy behavior were not desired is when
setting an optional+nullable value. In that case `default=null` would
also be needed and we could therefor imply `nullable=true` without
requiring it in the configuration.
These changes allow cloud blocks to be overridden by backend blocks and
vice versa; the logic follows the current backend behavior of a block
overriding a preceding block in full, with no merges.
An earlier commit added logic to decode "moved" blocks and do static
validation of them. Here we now include that result also in modules
produced from those files, which we can then use in Terraform Core to
actually implement the moves.
This also places the feature behind an active experiment keyword called
config_driven_move. For now activating this doesn't actually achieve
anything except let you include moved blocks that Terraform will summarily
ignore, but we'll expand the scope of this in later commits to eventually
reach the point where it's really usable.
This is part of a general effort to move all of Terraform's non-library
package surface under internal in order to reinforce that these are for
internal use within Terraform only.
If you were previously importing packages under this prefix into an
external codebase, you could pin to an earlier release tag as an interim
solution until you've make a plan to achieve the same functionality some
other way.
Martin Atkins