When helping folks in the community forum, I commonly see questions around
more complex patterns in transforming deep data structures into different
shapes to work with for_each. We have examples of these patterns in the
docs for the functions that they rely on, but they were not previously
very discoverable in the main configuration language documentation
sections.
Here I've moved the "Using Expressions in for_each" subsection on the
Resources page above some of the other sub-sections to hopefully make it
easier to see, and written out in more detail the two specific patterns
that answer a significant number of for_each-related user questions in
the hope that readers will be more likely to realize that the links are
relevant to what their goals.
I also added some more elaboration about the behavior of converting from
list to set in the "Using Sets" subsection, because this feature is often
a user's first encounter with the set data type and I've inferred from
some of the questions I've answered that a number of Terraform users don't
have prior experience with set data types in other languages to draw
assumptions from.
Finally, I added some similar links to the for_each patterns within the
for expression documentation itself, to try to make those examples more
visible to those who might be discovering the documentation in a different
sequence, e.g. by following a deep link shared in an answer to a question
in the community forum.
The "apply" documentation contained a simple typo, while the "plan"
documentation contained outdated information about using
"terraform plan PLANFILE" to view a plan. The latter is now a separate
command entirely, since Terraform 0.12: "terraform show PLANFILE".
This is a baby-step towards an intended future where all Terraform actions
which have side-effects in either remote objects or the Terraform state
can go through the plan+apply workflow.
This initial change is focused only on allowing plan+apply for changes to
root module output values, so that these can be written into a new state
snapshot (for consumption by terraform_remote_state elsewhere) without
having to go outside of the primary workflow by running
"terraform refresh".
This is also better than "terraform refresh" because it gives an
opportunity to review the proposed changes before applying them, as we're
accustomed to with resource changes.
The downside here is that Terraform Core was not designed to produce
accurate changesets for root module outputs. Although we added a place for
it in the plan model in Terraform 0.12, Terraform Core currently produces
inaccurate changesets there which don't properly track the prior values.
We're planning to rework Terraform Core's evaluation approach in a
forthcoming release so it would itself be able to distinguish between the
prior state and the planned new state to produce an accurate changeset,
but this commit introduces a temporary stop-gap solution of implementing
the logic up in the local backend code, where we can freeze a snapshot of
the prior state before we take any other actions and then use that to
produce an accurate output changeset to decide whether the plan has
externally-visible side-effects and render any changes to output values.
This temporary approach should be replaced by a more appropriately-placed
solution in Terraform Core in a release, which should then allow further
behaviors in similar vein, such as user-visible drift detection for
resource instances.
Resource destroy nodes can only depend on other resources. Connecting
them to their module expander can introduce cycles when the module
expander depends on resources in the destroyer's subgraph.
We don't need another node type for orphaned outptus, they are just
outputs being removed for a different reason than destroy. Use the
NodeDestroyableOutput implementation.
Destroy outputs also don't need to be referencers, since they are being
removed.
Rename DestroyOutputTransformer to destroyRootOutputTransformer, and add
an explanation as to why it is the only transformer that requires an
exception to know when it's involved from the destroy command.
simplification allows us to settle on a single interface,
graphNodeExpandsInstances for all types if instance expanders. The only
other specific class of resource we need to detect during pruning is the
nodeExpandApplyableResource node, which is already classified under the
GraphNodeResourceInstance interface.
ModulePath was incorrectly returning the parent module, because it did
not implement ReferenceOutside. With ReferenceOutside working correctly,
we can have ModulePath return the real path and remove the special case
for this during pruning.
Create a single transformer to remove all unused nodes from the apply
graph. This is similar to the combination of the resource pruning done
in the destroy edge transformer, and the unused values transformer. In
addition to resources, variables, locals, and outputs, we now need to
remove unused module expansion nodes as well. Since these can all be
interdependent, we need to process them as whole in a single
transformation.
In order for depends_on to work, modules need to implicitly depend on
their child modules. This will have little effect on terraform's
concurrency, as configuration trees are always much wider than they are
deep.
create interfaces that nodes can implement to declare whether they
expand into instances of some sort, using the instances.Expander, and/or
whether use the instances.Expander to find instances.
included is a rough transformer implementation to remove these nodes
from the apply graph.
All of the feedback from the experiment described enhancements that can
potentially be added later without breaking changes, so this change simply
removes the experiment gate from the feature as originally implemented
with no changes to its functionality.
Further enhancements may follow in later releases, but the goal of this
change is just to ship the feature exactly as it was under the experiment.
Most of the changes here are cleaning up the experiment opt-ins from our
test cases. The most important parts are in configs/experiments.go and in
experiments/experiment.go .
Fetching a default namespace provider from the public registry can
result in 404 Not Found error. This might be caused by a previously-
default provider moving to a new namespace, which means that the
configuration needs to be upgraded to use an explicit provider source.
This commit adds a more detailed diagnostic for this situation,
suggesting that the intended provider might be in a new namespace. The
recommended course of action is to run the 0.13upgrade command to
generate the correct required_providers configuration.
This adds supports for "unmanaged" providers, or providers with process
lifecycles not controlled by Terraform. These providers are assumed to
be started before Terraform is launched, and are assumed to shut
themselves down after Terraform has finished running.
To do this, we must update the go-plugin dependency to v1.3.0, which
added support for the "test mode" plugin serving that powers all this.
As a side-effect of not needing to manage the process lifecycle anymore,
Terraform also no longer needs to worry about the provider's binary, as
it won't be used for anything anymore. Because of this, we can disable
the init behavior that concerns itself with downloading that provider's
binary, checking its version, and otherwise managing the binary.
This is all managed on a per-provider basis, so managed providers that
Terraform downloads, starts, and stops can be used in the same commands
as unmanaged providers. The TF_REATTACH_PROVIDERS environment variable
is added, and is a JSON encoding of the provider's address to the
information we need to connect to it.
This change enables two benefits: first, delve and other debuggers can
now be attached to provider server processes, and Terraform can connect.
This allows for attaching debuggers to provider processes, which before
was difficult to impossible. Second, it allows the SDK test framework to
host the provider in the same process as the test driver, while running
a production Terraform binary against the provider. This allows for Go's
built-in race detector and test coverage tooling to work as expected in
provider tests.
Unmanaged providers are expected to work in the exact same way as
managed providers, with one caveat: Terraform kills provider processes
and restarts them once per graph walk, meaning multiple times during
most Terraform CLI commands. As unmanaged providers can't be killed by
Terraform, and have no visibility into graph walks, unmanaged providers
are likely to have differences in how their global mutable state behaves
when compared to managed providers. Namely, unmanaged providers are
likely to retain global state when managed providers would have reset
it. Developers relying on global state should be aware of this.
Martin Atkins