Aside from the two special meta-arguments "connection" and "provisioner"
this is just our standard mapping from schema to conversion rules, using
the provisioner's configuration schema.
Due to a copy-paste error, this was using the message from the providers
map in a "module" block.
This new message is not particularly helpful, but we should only see it
for a configuration that wouldn't have been valid in 0.11 either, and so
it's unlikely to be displayed.
Although /intro/getting-started includes docs content, those pages currently
redirect to the Learn platform, and so shouldn't be affected by the large unfurl
image.
Although sets do not have indexed elements, in Terraform 0.11 and earlier
element(...) would work with sets because we'd automatically convert them
to lists on entry to HIL -- with an arbitrary-but-consistent ordering --
and this return an arbitrary-but-consistent element from the list.
The element(...) function in Terraform 0.12 does not allow this because it
is not safe in general, but there was an existing pattern relying on this
in Terraform 0.11 configs which this upgrade rule is intended to preserve:
resource "example" "example" {
count = "${length(any_set_attribute)}"
foo = "${element(any_set_attribute, count.index}"
}
The above works because the exact indices assigned in the conversion are
irrelevant: we're just asking Terraform to create one resource for each
distinct element in the set.
This upgrade rule therefore inserts an explicit conversion to list if it
is able to successfully provide that the given expression will return a
set type:
foo = "${element(tolist(any_set_attribute), count.index}"
This makes the conversion explicit, allowing users to decide if it is
safe and rework the configuration if not. Since our static type analysis
functionality focuses mainly on resource type attributes, in practice this
rule will only apply when the given expression is a statically-checkable
resource reference. Since sets are an SDK-only concept in Terraform 0.11
and earlier anyway, in practice that works out just right: it's not
possible for sets to appear anywhere else in older versions anyway.
The comma-separated syntax is now reserved only for object constructor
expressions in attribute values, so the upgrade tool rewrites block
arguments to be newline-separated instead.
This was already working but we didn't have an explicit test for it until
now.
Prior to Terraform 0.12, ignore_changes was implemented in a
flatmap-oriented fashion and so users found that they could (and in fact,
were often forced to) use the internal .% and .# suffixes flatmap uses to
ignore changes to the number of elements in a list or map.
Terraform 0.12 no longer uses that representation, so we'll interpret
ignoring changes to the length as ignoring changes to the entire
collection. While this is not a totally-equivalent change, in practice
this pattern was most often used in conjunction with specific keys from a
map in order to _effectively_ ignore the entire map, even though Terraform
didn't really support that.
Martin Atkins