Terraform 0.11 and prior had an odd special case where a resource
attribute access for "count" would be resolved as the count for the
whole resource, rather than as an attribute of an individual instance as
for all other attributes.
Because Terraform 0.12 makes test_instance.foo appear as a list when count
is set (so it can be used in other expressions), it's no longer possible
to have an attribute in that position: lists don't have attributes.
Fortunately we don't really need that special case anymore since it
doesn't do anything we can't now do with the length(...) function.
This upgrade rule, then, detects references like test_instance.foo.count
and rewrites to length(test_instance.foo). As a special case, if
test_instance.foo doesn't have "count" set then it just rewrites as the
constant 1, which mimics what would've happened in that case in Terraform
0.11.
Prior to Terraform v0.12 it was possible for a provider to secretly set
some default arguments for the "connection" block, which most commonly
included a hard-coded type of "ssh" and a value from "host".
In the interests of "explicit is better than implicit", Terraform 0.12 no
longer has this feature and instead requires connection settings to be
written explicitly in terms of the resource's exported attributes. For
compatibility though, the upgrade tool will insert expressions that are
as close as possible to the logic the provider formerly implemented, or
in a few rare cases a TF-UPGRADE-TODO comment to fix it up manually.
Some of the existing resource type implementations have incredibly
complicated implementations of selecting a single host IP address to use
and don't expose the result of that as an attribute, so for now we handle
those via a complicated Terraform language expression achieving the same
result. Ideally these providers would introduce a new attribute that
exports the same address formerly exported as the hostname before their
initial v0.12-compatible release, in which case we can simplify these to
just reference the attribute in question. That would be preferable also
because it would allow use of that exported attribute in other contexts,
such as in a null_resource provisioner somewhere else or in an output
to allow a caller to deal with the SSH part itself.
This uses the fixed "superset" schema from the main terraform package to
apply our standard expression mapping, with the exception of "type" where
interpolation sequences are not supported due to the type being evaluated
early to retrieve the schema for decoding the rest.
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.
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.
HIL implemented its type conversions by rewriting its AST to include calls
to some undocumented builtin functions. Unfortunately those functions were
still explicitly callable if you could figure out the name for them, and
so they may have been used in the wild.
In particular, __builtin_StringToFloat was used as part of a workaround
for a HIL design flaw where it would prefer to convert strings to integers
rather than floats when performing arithmetic operations. This issue was,
indeed, the main reason for unifying int ant float into a single number
type in HCL. Since we published that as a suggested workaround, the
upgrade tool ought to fix it up.
The other cases have never been documented as a workaround, so they are
less likely to appear in the wild, but we might as well fix them up anyway
since we already have the conversion functions required to get the same
result in the new language.
To be safe/conservative, most of these convert to _two_ function calls
rather than just one, which ensures that these new expressions retain the
behavior of implicitly converting to the source type before running the
conversion. The new conversion functions only specify target type, and so
cannot guarantee identical results if the argument type does not exactly
match what was previously given as the parameter type in HIL.
HEREDOC tokens are a little more fussy than normal string sequences
because we need to preserve the whitespace within them along with the
start and end markers while we upgrade any interpolated expressions inside.
We need to do some work locally here because the HCL heredoc processing
"does too much" and throws away information we need to do a faithful
upgrade.
We also need to contend with the fact that Terraform <=0.11 had an older
version of HCL that accidentally permitted a degenerate form of heredoc
where the marker was at the end of the final line, like this:
degenerate = <<EOT
this should never have workedEOT
When we migrate this, we'll introduce the additional newline that is now
required, which will unfortunately slightly change the result string to
include a newline when parsed by 0.12, and so we'll need to call this out
as a caveat in the upgrade guide.
Previously, configupgrade would panic if it encountered a HEREDOC. For
the time being, we will simply print out the HEREDOC as-is.
Unfortunately, we discovered that terraform 0.11's version of HCL
allowed for HEREDOCs with the termination delimiter inline (instead of
on a newline, which is technically correct). Since 0.12configupgrade
needs to be bug-compatible with terraform 0.11, we must roll back to the
same version of HCL used in terraform 0.11.
In prior versions, we recommended using hash functions in conjunction with
the file function as an idiom for detecting changes to upstream blobs
without fetching and comparing the whole blob.
That approach relied on us being able to return raw binary data from
file(...). Since Terraform strings pass through intermediate
representations that are not binary-safe (e.g. the JSON state), there was
a risk of string corruption in prior versions which we have avoided for
0.12 by requiring that file(...) be used only with UTF-8 text files.
The specific case of returning a string and immediately passing it into
another function was not actually subject to that corruption risk, since
the HIL interpreter would just pass the string through verbatim, but this
is still now forbidden as a result of the stricter handling of file(...).
To avoid breaking these use-cases, here we introduce variants of the hash
functions a with "file" prefix that take a filename for a disk file to
hash rather than hashing the given string directly. The configuration
upgrade tool also now includes a rule to detect the documented idiom and
rewrite it into a single function call for one of these new functions.
This does cause a bit of function sprawl, but that seems preferable to
introducing more complex rules for when file(...) can and cannot read
binary files, making the behavior of these various functions easier to
understand in isolation.
In early versions of Terraform where the interpolation language didn't
have any real list support, list brackets around a single string was the
signal to split the string on a special uuid separator to produce a list
just in time for processing, giving expressions like this:
foo = ["${test_instance.foo.*.id}"]
Logically this is weird because it looks like it should produce a list
of lists of strings. When we added real list support in Terraform 0.7 we
retained support for this behavior by trimming off extra levels of list
during evaluation, and inadvertently continued relying on this notation
for correct type checking.
During the Terraform 0.10 line we fixed the type checker bugs (a few
remaining issues notwithstanding) so that it was finally possible to
use the more intuitive form:
foo = "${test_instance.foo.*.id}"
...but we continued trimming off extra levels of list for backward
compatibility.
Terraform 0.12 finally removes that compatibility shim, causing redundant
list brackets to be interpreted as a list of lists.
This upgrade rule attempts to identify situations that are relying on the
old compatibility behavior and trim off the redundant extra brackets. It's
not possible to do this fully-generally using only static analysis, but
we can gather enough information through or partial type inference
mechanism here to deal with the most common situations automatically and
produce a TF-UPGRADE-TODO comment for more complex scenarios where the
user intent isn't decidable with only static analysis.
In particular, this handles by far the most common situation of wrapping
list brackets around a splat expression like the first example above.
After this and the other upgrade rules are applied, the first example
above will become:
foo = test_instance.foo.*.id
This is a temporary implementation of these rules just so that these can
be passed through verbatim (rather than generating an error) while we
do testing of other features.
A subsequent commit will finish these with their own custom rulesets.
The main tricky thing here is ignore_changes, which contains strings that
are better given as naked traversals in 0.12. We also handle here mapping
the old special case ["*"] value to the new "all" keyword.
Both resource blocks and module blocks contain references to providers
that are expressed as short-form provider addresses ("aws.foo" rather than
"provider.aws.foo").
These rules call for those to be unwrapped as naked identifiers during
upgrade, rather than appearing as quoted strings. This also introduces
some further rules for other simpler meta-arguments that are required
for the test fixtures for this feature.
Some further rules are required here to deal with the meta-arguments we
accept inside these blocks, but this is good enough to pass through most
module blocks using the standard attribute-expression-based mapping.
Prior to v0.12 Terraform was liberal about these and allowed them to
mismatch, but now it's important to get this right so that resources
and resource instances can be used directly as object values, and so
we'll fix up any sloppy existing references so things keep working as
expected.
This is particularly important for the pattern of using count to create
conditional resources, since previously the "true" case would create one
instance and Terraform would accept an unindexed reference to that.
The reference syntax is not significantly changed, but there are some
minor additional restrictions on identifiers in HCL2 and as a special case
we need to rewrite references to data.terraform_remote_state .
Along with those mandatory upgrades, we will also switch references to
using normal index syntax where it's safe to do so, as part of
de-emphasizing the old strange integer attribute syntax (like foo.0.bar).
Users discovered that they could exploit some missing validation in
Terraform v0.11 and prior to treat block types as if they were attributes
and assign dynamic expressions to them, with some significant caveats and
gotchas resulting from the fact that this was never intended to work.
However, since such patterns are in use in the wild we'll convert them
to a dynamic block during upgrade. With only static analysis we must
unfortunately generate a very conservative, ugly dynamic block with
every possible argument set. Users ought to then clean up the generated
configuration after confirming which arguments are actually required.
If lookup is being used with only two arguments then it is equivalent to
index syntax and more readable that way, so we'll replace it.
Ideally we'd do similarly for element(...) here but sadly we cannot
because we can't prove in static analysis that the user is not relying
on the modulo wraparound behavior of that function.
We now have native language features for declaring tuples and objects,
which are the idiomatic way to construct sequence and mapping values that
can then be converted to list, set, and map types as needed.
In the old world, lists and maps could be created either using functions
in HIL or list/object constructs in HCL. Here we ensure that in the HCL
case we'll apply any required expression transformations to the individual
items within HCL's compound constructs.
The old parser was forgiving in allowing the use of block syntax where a
map attribute was expected, but the new parser is not (in order to allow
for dynamic map keys, for expressions, etc) and so the upgrade tool must
fix these to use attribute syntax.
This covers all of the expression node types in HIL's AST, and also
includes initial support for some of our top-level blocks so that we can
easily test that.
The initial implementations of the "variable" and "output" blocks are
pretty redundant and messy, so we can hopefully improve on these in a
later pass.
This function is the main functionality of this package. So far it just
deals with detecting and renaming JSON files that are mislabeled as
native syntax files. Other functionality will follow in later commits.
This package will do all of its work in-memory so that it can avoid making
partial updates and then failing, so we need to be able to load the
sources files from a particular directory into memory.
The upgrade process isn't idempotent, so we also attempt to detect
heuristically whether an upgrade has already been performed (can parse
with the new parser and has a version constraint that prevents versions
earlier than 0.12) so that the CLI tool that will eventually wrap this
will be able to produce a warning and prompt for confirmation in that
case.
Martin Atkins