This adopts a more guide-like writing style, similar to what prior commits
have done to some other subsections of this section.
In the process of writing this, I identified some unclear statements in
the "Resources" subsection, and so these are also revised here for
consistency with the output values documentation.
These revisions reflect this sub-section's new earlier placement in the
sub-section list, leading to a more guide-like style for the initial
sections.
Also includes some minor copy-editing to align terminology with that
introduced in the prior commit for the "Resources" docs page.
This is now the leading subsection of the Configuration section of the
docs, and so this rewrite intends to make it more "guide-like" and as
accessible as possible to those who are not yet familiar with other
Terraform concepts.
This rewrite also attempts to introduce some consistency into our
vocabulary, which should eventually be reflected throughout our
documentation. In particular:
- "Resource" refers to the block the user writes in configuration, while
"Resource _Type_" refers to what the provider defines. We previously
used "resource" for both of these interchangeably.
- "Resource" is no longer used to refer to what gets created and managed
in remote APIs as a result of a resource block in configuration. Lacking
a good distinct name for these, this guide uses the word "object",
qualifying it as "infrastructure object" or "remote object" where
necessary to retain clarity. This distinction is important to enable
a clear description of resource lifecycle.
- "Argument" refers to an element (attribute or block) within a resource
block. This terminology was already being used in some places, so we
embrace it here as a way to distinguish from "attribute", which is
what a resource _exports_ for use in expressions.
- Since interpolation is no longer needed to use expressions in the
language, the word "expression" is used to describe the definition of
a value that might involve some computation. Where necessary, this is
used with a modifier "arbitrary expression" to contrast with situations
where the set of allowed expression constructs is constrained.
The prior content on this page was little more than an instruction to
begin navigating the sub-sections of this section.
The new content aims to give a broad overview of some of the language
concepts and a syntax example, in order to create some context to help
the user navigate the subsections more easily.
This also introduces for the first time usage of the term "the Terraform
language". This was previously left un-named, leading to some awkward
sentence constructions elsewhere in the docs. This new name gives us
some specific terminology to use in order to contrast the language that
exists at Terraform's level of abstraction, defining the semantics, from
the underlying grammar provided by HCL.
With the additional configuration language features coming in Terraform
v0.12, our existing documentation structure is beginning to strain.
Here we reorganize the navigation slightly in order to introduce the
concepts in a more appropriate order so that we can reveal complexity
more gradually. Subsequent commits will revise the content of these
pages to better reflect the new sequencing.
The "Environment Variables" page is moved from the Configuration section
into the "Commands" section, since it is not considered a part of the
configuration language and thus more appropriate in the CLI documentation.
The old placement is reflective of the broader purpose that the
"Configuration" section had originally, but its new focus will be on
the Terraform language (.tf files) in particular, with other aspects of
customizing Terraforms behavior covered in other sections.
A number of our test fixtures were previously using the non-idiomatic form
of including a single child attribute all on one line with the block
header and bounding braces.
This non-idiomatic form is an error in HCL2, and hclfmt has always "fixed"
it to the expected form of each attribute being on a line of its own, and
so here we just update all the affected test fixtures to canonical form
(using hclfmt), allowing them to be parsed as intended.
Since the these entire files were processed with hclfmt, there are some
other unrelated style changes included in situations where the file
layouts were non-idiomatic in other ways.
These are all things that ought to be present in normal use but can end up
being nil in incorrect tests. Test debugging is simpler if these things
return errors gracefully, rather than crashing.
While there's no good reason for this to happen in practice, it can arise
in tests if mocks aren't set up quite right, and so we'll catch it and
report it nicely to make test debugging a little easier.
There's actually no good reason for this to happen in the normal case, but
it can happen reasonably easy if a test doesn't properly configure the
MockEvalContext, and so having this check here makes test debugging a
little easier.
Since this test case is using t.Run, it must be sure to pass the nested
*testing.T over to the testDiffs function or else calls to t.Fatal will
crash the whole test process, since they would otherwise be called on the
wrong instance of *testing.T.
The only reason these cases are arising right now is because we have tests
that haven't yet been updated to properly support schema, but it can't
hurt to add some robustness here to reduce the risk of real crashes.
Previously we had a panic in here for invalid resource modes. While that
does always indicate a programming error, it's frustrating to have a
crasher inside a String method since it often impedes our ability to
report an error properly, since the error reporting itself can crash.
Instead we'll just return an invalid string and hope the caller really is
bailing out with an error message.
After the refactoring to integrate HCL2 many of the tests were no longer
using correct types, attribute names, etc.
This is a bulk update of all of the tests to make them compile again, with
minimal changes otherwise. Although the tests now compile, many of them
do not yet pass. The tests will be gradually repaired in subsequent
commits, as we continue to complete the refactoring and retrofit work.
These helpers, similar to other such methods on ModuleInstance, are useful
for programmatically constructing provider config addresses, particularly
in tests where this is more straightforward than parsing from strings.
This now uses the HCL2 parser and evaluator APIs and evaluates in terms
of a new-style *lang.Scope, rather than the old terraform.Interpolator
type that is no longer functional.
The Context.Eval method used here behaves differently than the
Context.Interpolater method used previously: it performs a graph walk
to populate transient values such as input variables, local values, and
output values, and produces its scope in terms of the result of that
graph walk. Because of this, it is a lot more robust than the prior method
when asked to resolve references other than those that are persisted
in the state.
Some of the objects that are referencable from expressions are transient
values computed only during a graph walk, and not persisted in state. In
order to support arbitrary evaluation of expressions, such as in the
"terraform console" CLI command, it's necessary to be able to evaluate
these values before we start evaluating.
This new Eval method achieves this by performing a special graph walk that
ignores resources (except for dependency resolution) and just focuses on
evaluating all of these transient values, before returning an evaluation
scope that can then resolve expressions in terms of that result.
This replaces the Context.Interpolator method, which was fraught with
various issues due to it not properly priming the state before evaluating.
Here we replace the stub implementations in evaluationStateData with real
implementations that are based on their equivalents in the old
Interpolator type.
The behavior here is a little different due to the different semantics
expected under HCL2, but the principle remains the same: the main
references are resolved from the state, using config for validation
in order to produce some helpful error messages.
I took some missteps here while doing the initial refactor for HCL2 types.
This restores the map of maps that retains all of the variable values, and
then makes it available to the evaluator.
Previously our evaluationStateData object was constructed inside
Evaluator.Scope, but this was awkward because all of the fields inside it
need to be populated from BuiltinEvalContext fields, and so the signature
of Evaluator.Scope kept growing new arguments over time.
Instead, we reassign the responsibilities here so that Evaluator.Scope
takes an already-constructed lang.Data, and then teach BuiltinEvalContext
to build this object itself from its own internal values.
Due to a logic error here we were trying to find our our module's parent
as a descendent of itself, rather than as a descendent of the root. It
turns out that we can do this even more simply by just accessing the
Parent field on the given config, avoiding the need to traverse the tree
down from the root at all.
While here, this also switches to using the path.Call helper method rather
than manually slicing the path array, since this better communicates our
intent.
This is a little awkward since we need to instantiate the providers much
earlier than before. To avoid a lot of reshuffling here we just spin each
one up and then immediately shut it down again, letting our existing init
functionality during the graph walk still do the main initialization.
Throughout the main "terraform" package we identify resources using the
address types, and so this helper is useful to make concise transitions
between the address types and the configuration types.
As part of this, we use the address types to produce the keys used in our
resource maps. This has no visible change in behavior since the prior
implementation produced an equal result, but this change ensures that
ResourceByAddr cannot be broken by hypothetical future changes to the
key serialization.
These particular shims will have a pretty limited lifetime in mainline
Terraform code (primarily to stub out the new expression evaluator against
the old state structs until the new format is implemented) but will live
on for some time in state migration and provider plugin compatibility
shims.
Previously an empty diagnostics would appear as "null" in the JSON output,
since that is how encoding/json serializes a nil slice. It's more
convenient for users of dynamic languages to keep the type consistent
in all cases, since they can then just iterate the list without needing a
special case for when it is null.
We can only do this when modules are loaded with Parser.LoadConfigDir,
but in practice this is the common case anyway.
This is important to support the path.module and path.root expressions in
configuration.
addrs.Module is itself internally just []string, but this better
communicates our intent here and makes this integrate better with other
code which is using this type for this purposes.
We've not yet adjusted any of the state structs to reflect our new address
types because they are used with encoding/json to produce our state file
format, but the shimming here previously was incorrect because it failed
to include the special "root" string that's always required at element
zero of a module path in the state.
Due to how deeply the configuration types go into Terraform Core, there
isn't a great way to switch out to HCL2 gradually. As a consequence, this
huge commit gets us from the old state to a _compilable_ new state, but
does not yet attempt to fix any tests and has a number of known missing
parts and bugs. We will continue to iterate on this in forthcoming
commits, heading back towards passing tests and making Terraform
fully-functional again.
The three main goals here are:
- Use the configuration models from the "configs" package instead of the
older models in the "config" package, which is now deprecated and
preserved only to help us write our migration tool.
- Do expression inspection and evaluation using the functionality of the
new "lang" package, instead of the Interpolator type and related
functionality in the main "terraform" package.
- Represent addresses of various objects using types in the addrs package,
rather than hand-constructed strings. This is not critical to support
the above, but was a big help during the implementation of these other
points since it made it much more explicit what kind of address is
expected in each context.
Since our new packages are built to accommodate some future planned
features that are not yet implemented (e.g. the "for_each" argument on
resources, "count"/"for_each" on modules), and since there's still a fair
amount of functionality still using old-style APIs, there is a moderate
amount of shimming here to connect new assumptions with old, hopefully in
a way that makes it easier to find and eliminate these shims later.
I apologize in advance to the person who inevitably just found this huge
commit while spelunking through the commit history.
Our new "addrs" package gives us some nice representations of various
kinds of "address" within Terraform. To talk to APIs that use these, it's
convenient to be able to easily derive such addresses from the
configuration objects.
These new methods, along with a recasting of the existing
Resource.ProviderConfigKey method to Resource.ProviderConfigAddr, give us
some key integration points to support the configuration graph transforms
in the main "terraform" package.
This helper deals with the address wrangling required to find the address
that a provider configuration might inherit from if no explicit
configuration is given and instead configuration is taken from the
parent module.
This method is not generally useful, and is here mainly just to help the
provider-related graph transformations in the main terraform package.
This "kitchen sink" commit is mainly focused on supporting "targets" as
a new sub-category of addresses, for use-case like the -target CLI option,
but also includes some other functionality to get closer to replacing
terraform.ResourceAddress and fill out some missing parts for representing
various other address types that are currently represented as strings
in the "terraform" package.
This was accidentally missed on the first pass of module call decoding.
As before, this is a map from child provider config address to parent
provider config address, allowing the set of providers to be projected in
arbitrary ways into a child module.
This is for parsing the type of provider configuration address we write
into state in order to remember which provider configuration is
responsible for each resource.
This is currently not very ergonomic due to the API exposed by providers.
We'll smooth this out in a later change to improve the provider API, since
we know we always want the entire schema.
There is some existing practice in the "terraform" package of returning
a special error type ValidationError from EvalNode implementations in
order to return warnings without halting the graph walk even though a
non-nil error was returned.
This is a diagnostics-flavored version of that approach, allowing us to
avoid totally reworking the EvalNode concept around diagnostics and
retaining the ability to return non-fatal errors.
NonFatalErr is equivalent to the former terraform.ValidationError, while
ErrWithWarnings is a helper that automatically treats any errors as
fatal but returns NonFatalError if the diagnostics contains only warnings.
This is a built-in implementation of ModuleWalker that just returns an
error any time it's asked for a module. This is intended for simple unit
tests where no child modules are needed anyway.
This is useful for creating a valid placeholder configuration, but not
much else. Most callers should use BuildConfig to build a configuration
that actually has something in it.
Martin Atkins