During the Terraform 0.12 work we briefly had a partial update of the old
Terraform 0.11 (and prior) diff renderer that could work with the new
plan structure, but could produce only partial results.
We switched to the new plan implementation prior to release, but the
"terraform show" command was left calling into the old partial
implementation, and thus produced incomplete results when rendering a
saved plan.
Here we instead use the plan rendering logic from the "terraform plan"
command, making the output of both identical.
Unfortunately, due to the current backend architecture that logic lives
inside the local backend package, and it contains some business logic
around state and schema wrangling that would make it inappropriate to move
wholesale into the command/format package. To allow for a low-risk fix to
the "terraform show" output, here we avoid some more severe refactoring by
just exporting the rendering functionality in a way that allows the
"terraform show" command to call into it.
In future we'd like to move all of the code that actually writes to the
output into the "command" package so that the roles of these components
are better segregated, but that is too big a change to block fixing this
issue.
As mentioned in #17871 the current example can hide the fact that the module
path plays an important role. The example's explanation is expanded.
Moreover, the verb "attach" is replaced with "map" to make the vocabulary
consistent with the wording in the documentation of the terraform state.
For remote operations, the remote system (Terraform Cloud or Enterprise)
writes the stored variable values into a .tfvars file before running the
remote copy of Terraform CLI.
By contrast, for operations that only run locally (like
"terraform import"), we fetch the stored variable values from the remote
API and add them into the set of available variables directly as part
of creating the local execution context.
Previously in the local-only case we were assuming that all stored
variables are strings, which isn't true: the Terraform Cloud/Enterprise UI
allows users to specify that a particular variable is given as an HCL
expression, in which case the correct behavior is to parse and evaluate
the expression to obtain the final value.
This also addresses a related issue whereby previously we were forcing
all sensitive values to be represented as a special string "<sensitive>".
That leads to type checking errors for any variable specified as having
a type other than string, so instead here we use an unknown value as a
placeholder so that type checking can pass.
Unpopulated sensitive values may cause errors downstream though, so we'll
also produce a warning for each of them to let the user know that those
variables are not available for local-only operations. It's a warning
rather than an error so that operations that don't rely on known values
for those variables can potentially complete successfully.
This can potentially produce errors in situations that would've been
silently ignored before: if a remote variable is marked as being HCL
syntax but is not valid HCL then it will now fail parsing at this early
stage, whereas previously it would've just passed through as a string
and failed only if the operation tried to interpret it as a non-string.
However, in situations like these the remote operations like
"terraform plan" would already have been failing with an equivalent
error message anyway, so it's unlikely that any existing workspace that
is being used for routine operations would have such a broken
configuration.
We need to be able to reference all possible dependencies for ordering
when the configuration is no longer present, which means that absolute
addresses must be used. Since this is only to recreate the proper
ordering for instance destruction, only resources addresses need to be
listed rather than individual instance addresses.
The fallback type for GetResource from an EachMap is a cty.Object,
because resource schemas may contain dynamically typed attributes.
Check for an Object type in the evaluation of self, to use the proper
GetAttr method when extracting the value.
These are often confusing for new contributors, since this looks
suspiciously like the right place to add new functions or change the
behavior of existing ones.
To reduce that confusion, here we remove them entirely from this package
(which is now dead code in Terraform 0.12 anyway) and include in the
documentation comments a pointer to the current function implementations.
If a resource is only destroying instances, there is no reason to
prepare the state and we can remove the Resource (prepare state) nodes.
They normally have pose no issue, but if the instances are being
destroyed along with their dependencies, the resource node may fail to
evaluate due to the missing dependencies (since destroy happens in the
reverse order).
These failures were previously blocked by there being a cycle when the
destroy nodes were directly attached to the resource nodes.
Destroy nodes do not need to be connected to the resource (prepare
state) node when adding them to the graph. Destroy nodes already have a
complete state in the graph (which is being destroyed), any references
will be added in the ReferenceTransformer, and the proper
connection to the create node will be added in the
DestroyEdgeTransformer.
Under normal circumstances this makes no difference, as create and
destroy nodes always have an dependency, so having the prepare state
handled before both only linearizes the operation slightly in the
normal destroy-then-create scenario.
However if there is a dependency on a resource being replaced in another
module, there will be a dependency between the destroy nodes in each
module (to complete the destroy ordering), while the resource node will
depend on the variable->output->resource chain. If both the destroy and
create nodes depend on the resource node, there will be a cycle.
The CBDEdgeTransformer tests worked on fake data structures, with a
synthetic graph, and configs that didn't match. Update them to generate
a more complete graph, with real node implementations, from real
configs.
The output graph is filtered down to instances, and the results still
functionally match the original expected test results, with some minor
additions due to using the real implementation.
When looking for dependencies to fix when handling
create_before_destroy, we need to look past more than one edge, as
dependencies may appear transitively through outputs and variables. Use
Descendants rather than UpEdges.
We have the full graph to use for the CBD transformation, so there's no
longer any need to create a temporary graph, which may differ from the
original.
Martin Atkins