Previously we were attempting to infer the checkable object address kind
of a given address by whether it included "output" in the position where
a resource type name would otherwise go.
That was already potentially risky because we've historically not
prevented a resource type named "output", and it's also a
forward-compatibility hazard in case we introduce additional object kinds
with entirely-new addressing schemes in future.
Given that, we'll instead always be explicit about what kind of address
we're storing in a wire or file format, so that we can make sure to always
use the intended parser when reading an address back into memory, or
return an error if we encounter a kind we're not familiar with.
Our existing addrs.Checkable represents a particular (possibly-dynamic)
object that can have checks associated with it.
This new addrs.ConfigCheckable represents static configuration objects
that can potentially generate addrs.Checkable objects.
The idea here is to allow us to predict from the configuration a set of
potential checkable object containers and then dynamically associate
the dynamic checkable objects with them as we make progress with planning.
This is intended for our integration of checks into the "terraform test"
testing harness, to be used instead of the weirdo builtin provider we were
using as a placeholder before we had first-class syntax for checks.
Test reporting tools find it helpful for there to be a consistent set of
test cases from one run to the next so that they can report on trends over
multiple runs, and so our ConfigCheckable addresses will serve as the
relatively-static "test case" that we'll then associate the dynamic checks
with, so that we can still talk about objects in the test result report
even if we end up not reaching them due to an upstream conditution failure.
In order to include condition block results in the JSON plan output, we
must store them in the plan and its serialization.
Terraform can evaluate condition blocks multiple times, so we must be
able to update the result. Accordingly, the plan.Conditions object is a
map with keys representing the condition block's address. Condition
blocks are not referenceable in any other context, so this address form
cannot be used anywhere in the configuration.
The commit includes a new test case for the JSON output of a
refresh-only plan, which is currently the only way for a failing
condition result to be rendered through this path.
The whole point of UniqueKey is to deal with the fact that we have some
distinct address types which have an identical string representation, but
unfortunately that fact caused us to not notice that we'd incorrectly
made AbsResource.UniqueKey return a no-key instance UniqueKey instead of
its own distinct unique key type.
Since these address types are not directly comparable themselves, we use
an unexported named type around the string representation, whereby the
special type can avoid any ambiguity between string representations of
different types and thus each type only needs to worry about possible
ambiguity of its _own_ string representation.
Many times now we've seen situations where we need to use addresses
as map keys, but not all of our address types are comparable and thus
we tend to end up using string representations as keys instead.
That's problematic because conversion to string uses type information
and some of the address types have string representations that are
ambiguous with one another.
UniqueKey therefore represents an opaque key that is unique for each
functionally-distinct address across all types that implement
UniqueKeyer.
For this initial commit I've implemented UniqueKeyer only for the
Referenceable family of types. These are an easy case because they
were all already comparable (intentionally) anyway. Later commits
can implement UniqueKeyer for other types that are not naturally
comparable, such as any which include a ModuleInstance.
This also includes a new type addrs.Set which wraps a map as a set
of addresses, using the unique keys to ensure that there can be only
one element for each distinct address.
These three types represent the three different address representations we
need to represent different stages of analysis for "moved" blocks in the
configuration.
The goal here is to encapsulate all of the static address wrangling inside
these types so that users of these types elsewhere would have to work
pretty hard to use them incorrectly.
In particular, the MovableEndpoint type intentionally fully encapsulates
the weird relative addresses we use in configuration so that code
elsewhere in Terraform can never end up holding an address of a type that
suggests absolute when it's actually relative. That situation only occurs
in the internals of MoveableEndpoint where we use not-really-absolute
AbsMoveable address types to represent the not-yet-resolved relative
addresses.
This only takes care of the static address wrangling. There's lots of
other rules for what makes a "moved" block valid which will need to be
checked elsewhere because they require more context than just the content
of the address itself.
This PR adds decoding for the upcoming "moved" blocks in configuration. This code is gated behind an experiment called EverythingIsAPlan, but the experiment is not registered as an active experiment, so it will never run (there is a test in place which will fail if the experiment is ever registered).
This also adds a new function to the Targetable interface, AddrType, to simplifying comparing two addrs.Targetable.
There is some validation missing still: this does not (yet) descend into resources to see if the actual resource types are the same (I've put this off in part because we will eventually need the provider schema to verify aliased resources, so I suspect this validation will have to happen later on).
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.
