These follow the same principle as jsondecode and jsonencode, but use
YAML instead of JSON.
YAML has a much more complex information model than JSON, so we can only
support a subset of it during decoding, but hopefully the subset supported
here is a useful one.
Because there are many different ways to _generate_ YAML, the yamlencode
function is forced to make some decisions, and those decisions are likely
to affect compatibility with other real-world YAML parsers. Although the
format here is intended to be generic and compatible, we may find that
there are problems with it that'll we'll want to adjust for in a future
release, so yamlencode is therefore marked as experimental for now until
the underlying library is ready to commit to ongoing byte-for-byte
compatibility in serialization.
The main use-case here is met by yamldecode, which will allow reading in
files written in YAML format by humans for use in Terraform modules, in
situations where a higher-level input format than direct Terraform
language declarations is helpful.
This is similar to the function of the same name in Python, generating a
sequence of numbers as a list that can then be used in other
sequence-oriented operations.
The primary use-case for it is to turn a count expressed as a number into
a list of that length, which can then be iterated over or passed to a
collection function to produce that number of something else, as shown
in the example at the end of its documentation page.
A longer-form guide will follow in the Sentinel section of the Terraform
Enterprise documentation, once it's ready. For now, this section isn't
saying anything useful since it was always just a stub for a guide we
planned to write later.
The upgrade tool is assuming that a type of "list" means list(string) and
a type of "map" means map(string), because that was what we documented
those as meaning.
In practice, Terraform 0.11 was lacking some validation which allowed
more complex nested structures in some cases even though they were pretty
inconvenient to use due to other language limitations.
The upgrade tool doesn't have enough context to make a reliable decision
on this, so instead we'll rely on the upgrade guide for this. We don't
need a TF-UPGRADE-TODO comment in this case because we reserve those for
things where a subsequent operation might cause the configuration to be
misinterpred, rather than just causing an error. Instead, we'll show an
example of the comment in the upgrade guide so the reader can easily
match it, and give some advice in the guide on how to address it.
We've seen in the past that some users try to use this form with the
ssh:// URL prefix, so we'll mention explicitly that this is invalid and
show a working example of how to use it without the URL scheme prefix.
Our original upgrade guide was drafted while some things were still in
flux and not all of our upgrade tooling was in place yet.
This redraft now attempts to be more specific and direct, showing exact
commands to run and (where relevant) exact error messages that Terraform
might return.
I also took this opportunity for some general copy-editing, though we'll
probably want to do one more pass of that alone (without changing any
content at the same time) before final release.
This new content presumes the existence of a Terraform v0.11.14 release,
which isn't published yet at the time of writing but should be published
before v0.12.0 final, once we've done final verification and review of
the upgrade path including it.
- Note that we intentionally omitted it from the sidebar, to reduce confusion.
- Write a summary up top so you can stop reading sooner if you don't actually need this.
* lang/funcs: testing of functions through the lang package API
The function-specific unit tests do not cover the HCL conversion that happens when the functions are called in a terraform configuration. For e.g., HCL converts sets to lists before passing it to the function. This means that we could not test passing a set in the function _unit_ tests.
This adds a higher-level acceptance test, plus a check that every (pure) function has a test.
* website/docs: update function documentation
There was some leftover v0.11-style interpolation syntax here.
We prefer to use a "naked" expression in situations like this where the result
isn't a string, because interpolations returning non-strings is a common source
of confusion for new users.
The division operator now always performs floating point division, whereas
before it would choose between float and int division based on the types
of its arguments.
We have a specific error message for when a fractional number is used as
an index in HCL, but this additional upgrade guidance provides a specific
solution to the problem: the floor function.
Sadly we don't have enough context in the current design of the upgrade
tool to make this fix automatic. With some refactoring it may be possible
to apply the fix automatically within list brackets, but since that is
a relatively complex change we'll first try this manual solution prompted
by an error message, because in practice so far we've seen this reported
only in the context of list indexing and our error check will catch that
and make the user aware of the need for a fix there.
* funcs/coalesce: return the first non-null, non-empty element from a
sequence.
The go-cty coalesce function, which was originally used here, returns the
first non-null element from a sequence. Terraform 0.11's coalesce,
however, returns the first non-empty string from a list of strings.
This new coalesce function aims to preserve terraform's documented
functionality while adding support for additional argument types. The
tests include those in go-cty and adapted tests from the 0.11 version of
coalesce.
* website/docs: update coalesce function document
Martin Atkins