The ContextGraphWalker struct includes a lock that's passed down to
BuiltinEvalContext and guards access to interpolation variables as
they're written using SetVariables.
The likely problem being expressed in #5733 is that the same map
reference is also passed down to the Interpolater.Variables field, which
is used for variable lookup.
Here, we plumb the same lock we're using to guard access for writes down
and acquire it before doing variable reads as well. It's not as fine
grained as perhaps it could be, but all the context tests pass and I
believe this should address #5733.
References to computed list-ish attributes (set, list, map) were being
improperly resolved as an empty list `[]` during the plan phase (when
the value of the reference is not yet known) instead of as an
UnknownValue.
A "diffs didn't match" failure in an AWS DirectoryServices test led to
this discovery (and this commit fixes the failing test):
https://travis-ci.org/hashicorp/terraform/jobs/104812951
Refs #2157 which has the original work to support computed list
attributes at all. This is just a simple tweak to that work.
/cc @radeksimko
Building on the work of #3846, deprecate `filename` in favor of a
`template` attribute that accepts file contents instead of a path.
Required a bit of work in the interpolation code to prevent Terraform
from assuming that template interpolations were resource variables that
needed to be resolved. Leaving them as "Unknown Variables" prevents
interpolation from happening early and lets the `template_file` resource
do its thing.
This is the initial pure "all tests passing without a diff" stage. The
plan is to change the internal representation of StringList to include a
suffix delimiter, which will allow us to recognize empty and
single-element lists.
Instead of returning UnknownVariableValue every time, attempt to return
the real value. If we don't find it, return unknown value. This fixes
removing outputs from state on refresh.
This is not really improving the way we do interpolation so much as its
just shuffling bits around. I don't want to refactor interpolation in
this branch so I needed to make the current way reusable so that I can
reuse it in the new Context.
