Previously our graph walker expected to recieve a data structure
containing schemas for all of the provider and provisioner plugins used in
the configuration and state. That made sense back when
terraform.NewContext was responsible for loading all of the schemas before
taking any other action, but it no longer has that responsiblity.
Instead, we'll now make sure that the "contextPlugins" object reaches all
of the locations where we need schema -- many of which already had access
to that object anyway -- and then load the needed schemas just in time.
The contextPlugins object memoizes schema lookups, so we can safely call
it many times with the same provider address or provisioner type name and
know that it'll still only load each distinct plugin once per Context
object.
As of this commit, the Context.Schemas method is now a public interface
only and not used by logic in the "terraform" package at all. However,
that does leave us in a rather tenuous situation of relying on the fact
that all practical users of terraform.Context end up calling "Schemas" at
some point in order to verify that we have all of the expected versions
of plugins. That's a non-obvious implicit dependency, and so in subsequent
commits we'll gradually move all responsibility for verifying plugin
versions into the caller of terraform.NewContext, which'll heal a
long-standing architectural wart whereby the caller is responsible for
installing and locating the plugin executables but not for verifying that
what's installed is conforming to the current configuration and dependency
lock file.
Previously the graph builders all expected to be given a full manifest
of all of the plugin component schemas that they could need during their
analysis work. That made sense when terraform.NewContext would always
proactively load all of the schemas before doing any other work, but we
now have a load-as-needed strategy for schemas.
We'll now have the graph builders use the contextPlugins object they each
already hold to retrieve individual schemas when needed. This avoids the
need to prepare a redundant data structure to pass alongside the
contextPlugins object, and leans on the memoization behavior inside
contextPlugins to preserve the old behavior of loading each provider's
schema only once.
By tolerating ProviderSchema and ProvisionerSchema potentially returning
errors, we can slightly simplify EvalContextBuiltin by having it retrieve
individual schemas when needed directly from the "Plugins" object.
EvalContextBuiltin already needs to be holding a contextPlugins instance
for other reasons anyway, so this allows us to get the same result with
fewer moving parts.
The responsibility for actually instantiating a single plugin and reading
out its schema now belongs to the contextPlugins type, which memoizes the
results by each plugin's unique identifier so that we can avoid retrieving
the same schemas multiple times when working with the same context.
This doesn't change the API of Context.Schemas but it does restore the
spirit of an earlier version of terraform.Context which did all of the
schema loading proactively inside terraform.NewContext. In an earlier
commit we reduced the scope of terraform.NewContext, making schema loading
a separate step, but in the process of doing that removed the effective
memoization of the schema results that terraform.NewContext was providing.
The memoization here will play out in a different way than before, because
we'll be treating each plugin call as separate rather than proactively
loading them all up front, but this is effectively the same because all
of our operation methods on Context call Context.Schemas early in their
work and thus end up forcing all of the necessary schemas to load up
front nonetheless.
In the v0.12 timeframe we made contextComponentFactory an interface with
the expectation that we'd write mocks of it for tests, but in practice we
ended up just always using the same "basicComponentFactory" implementation
throughout.
In the interests of simplification then, here we replace that interface
and its sole implementation with a new concrete struct type
contextPlugins.
Along with the general benefit that this removes an unneeded indirection,
this also means that we can add additional methods to the struct type
without the usual restriction that interface types prefer to be small.
In particular, in a future commit I'm planning to add methods for loading
provider and provisioner schemas, working with the currently-unused new
fields this commit has included in contextPlugins, as compared to its
predecessor basicComponentFactory.
In earlier Terraform versions we used the set of all available plugins of
each type to make graph-building decisions, but in modern Terraform we
make those decisions based entirely on the configuration.
Consequently, we no longer need the methods which can enumerate all of the
known plugin components of a given type. Instead, we just try to
instantiate each of the plugins that the configuration refers to and then
handle the error when that fails, which typically means that the user
needs to run "terraform init" to install some new plugins.
In earlier incarnations of these transformers we used the set of all
available providers for tasks such as generating implied provider
configuration nodes.
However, in modern Terraform we can extract all of the information we need
from the configuration itself, and so these transformers weren't actually
using this set of provider addresses.
These also ended up getting left behind as sets of string rather than sets
of addrs.Provider in our earlier refactoring work, which didn't really
matter because the result wasn't used anywhere anyway.
Rather than updating these to use addrs.Provider instead, I've just
removed the unused arguments entirely in the hope of making it easier to
see what inputs these transformers use to make their decisions.
The public interface for loading schemas is Context.Schemas, which can
take into account the context's records of which plugin versions and
checksums we're expecting. loadSchemas is an implementation detail of
that, representing the part we run only after we've verified all of the
plugins.
This is the first test exercising the basic functionality of config-driven
move. We previously had it skipped because Terraform's previous design
of treating all three of the state artifacts as mutable attributes of
terraform.Context meant that it was too late during planning to deal with
the move operations, and thus this test was failing.
Thanks to the previous commit, which changes the terraform.Context API
such that we can defer creating the three state artifacts until we're
already doing planning, this test now works and shows Terraform correctly
handling a resource that was formerly called "a" and is now called "b",
with a "moved" block recording that renaming.
Previously terraform.Context was built in an unfortunate way where all of
the data was provided up front in terraform.NewContext and then mutated
directly by subsequent operations. That made the data flow hard to follow,
commonly leading to bugs, and also meant that we were forced to take
various actions too early in terraform.NewContext, rather than waiting
until a more appropriate time during an operation.
This (enormous) commit changes terraform.Context so that its fields are
broadly just unchanging data about the execution context (current
workspace name, available plugins, etc) whereas the main data Terraform
works with arrives via individual method arguments and is returned in
return values.
Specifically, this means that terraform.Context no longer "has-a" config,
state, and "planned changes", instead holding on to those only temporarily
during an operation. The caller is responsible for propagating the outcome
of one step into the next step so that the data flow between operations is
actually visible.
However, since that's a change to the main entry points in the "terraform"
package, this commit also touches every file in the codebase which
interacted with those APIs. Most of the noise here is in updating tests
to take the same actions using the new API style, but this also affects
the main-code callers in the backends and in the command package.
My goal here was to refactor without changing observable behavior, but in
practice there are a couple externally-visible behavior variations here
that seemed okay in service of the broader goal:
- The "terraform graph" command is no longer hooked directly into the
core graph builders, because that's no longer part of the public API.
However, I did include a couple new Context functions whose contract
is to produce a UI-oriented graph, and _for now_ those continue to
return the physical graph we use for those operations. There's no
exported API for generating the "validate" and "eval" graphs, because
neither is particularly interesting in its own right, and so
"terraform graph" no longer supports those graph types.
- terraform.NewContext no longer has the responsibility for collecting
all of the provider schemas up front. Instead, we wait until we need
them. However, that means that some of our error messages now have a
slightly different shape due to unwinding through a differently-shaped
call stack. As of this commit we also end up reloading the schemas
multiple times in some cases, which is functionally acceptable but
likely represents a performance regression. I intend to rework this to
use caching, but I'm saving that for a later commit because this one is
big enough already.
The proximal reason for this change is to resolve the chicken/egg problem
whereby there was previously no single point where we could apply "moved"
statements to the previous run state before creating a plan. With this
change in place, we can now do that as part of Context.Plan, prior to
forking the input state into the three separate state artifacts we use
during planning.
However, this is at least the third project in a row where the previous
API design led to piling more functionality into terraform.NewContext and
then working around the incorrect order of operations that produces, so
I intend that by paying the cost/risk of this large diff now we can in
turn reduce the cost/risk of future projects that relate to our main
workflow actions.
Here we wire through the "move results" into the graph walk data
structures so that all of the the nodes which produce
plans.ResourceInstanceChange values can capture the "PrevRunAddr" for
each resource instance.
This doesn't actually quite work yet, because the logic in Context.Plan
isn't actually correct and so the updated state from
refactoring.ApplyMoves isn't actually visible as the "previous run state".
For that reason, the context test in this commit is currently skipped,
with the intent of re-enabling it once the updated state is properly
propagating into the plan graph walk and thus we can actually react to
the result of the move while choosing actions for those addresses.
In order to expose the effect of any relevant "moved" statements we dealt
with prior to creating the plan, we'll record with each
ResourceInstanceChange both is current address and the address it was
tracked at for the previous run.
To save consumers of these objects from having to special-case the
situation where there _was_ no previous run (e.g. because this is a Create
change), we'll just pretend the previous run address was the same as the
current address in that case, the same as for an update without any
renaming in effect.
This includes a breaking change to the plan file format, but one that
doesn't require a version number increment because there is no ambiguity
between the two formats and so mismatched parsers will already fail with
an error message.
As of this commit we've just added the new field but not yet populated it
with any useful information: it always just matches Addr. A future commit
will wire this up to the result of applying the moves so that we can
populate it correctly. We also don't yet expose this new information
anywhere in the UI layer.
As of this commit, refactoring.ValidateMoves doesn't actually do anything
yet (always returns nil) but the goal here is to wire in the set of all
declared instances so that refactoring.ValidateMoves will then have all
of the information it needs to encapsulate our validation rules.
The actual implementation of refactoring.ValidateMoves will follow in
subsequent commits.
Up until now marks were not considered by `ignore_changes`, that however
means changes to sensitivity within a configuration cannot ignored, even
though they are planned as changes.
Rather than separating the marks and tracking their paths, we can easily
update the processIgnoreChanges routine to handle the marked values
directly. Moving the `processIgnoreChanges` call also cleans up some of
the variable naming, making it more consistent through the body of the
function.
This is a whole lot of nothing right now, just stubbing out some control
flow that ultimately just leads to TODOs that cause it to do nothing at
all.
My intent here is to get this cross-cutting skeleton in place and thus
make it easier for us to collaborate on adding the meat to it, so that
it's more likely we can work on different parts separately and still get
a result that tessellates.
The previous name didn't fit with the naming scheme for addrs types:
The "Abs" prefix typically means that it's an addrs.ModuleInstance
combined with whatever type name appears after "Abs", but this is instead
a ModuleCallOutput combined with an InstanceKey, albeit structured the
other way around for convenience, and so the expected name for this would
be the suffix "Instance".
We don't have an "Abs" type corresponding with this one because it would
represent no additional information than AbsOutputValue.
* terraform: use hcl.MergeBodies instead of configs.MergeBodies for provider configuration
Previously, Terraform would return an error if the user supplied provider configuration via interactive input iff the configuration provided on the command line was missing any required attributes - even if those attributes were already set in config.
That error came from configs.MergeBody, which was designed for overriding valid configuration. It expects that the first ("base") body has all required attributes. However in the case of interactive input for provider configuration, it is perfectly valid if either or both bodies are missing required attributes, as long as the final body has all required attributes. hcl.MergeBodies works very similarly to configs.MergeBodies, with a key difference being that it only checks that all required attributes are present after the two bodies are merged.
I've updated the existing test to use interactive input vars and a schema with all required attributes. This test failed before switching from configs.MergeBodies to hcl.MergeBodies.
* add a command package test that shows that we can still have providers with dynamic configuration + required + interactive input merging
This test failed when buildProviderConfig still used configs.MergeBodies instead of hcl.MergeBodies
As the comment notes, this hostname is the default for provide source
addresses. We'll shortly be adding some address types to represent module
source addresses too, and so we'll also have DefaultModuleRegistryHost
for that situation.
(They'll actually both contain the the same hostname, but that's a
coincidence rather than a requirement.)
Most legacy provider resources do not implement any import functionality
other than returning an empty object with the given ID, relying on core
to later read that resource and obtain the complete state. Because of
this, we need to check the response from ReadResource for a null value,
and use that as an indication the import id was invalid.
Do not convert provisioner diagnostics to errors so that users can get
context from provisioner failures.
Return diagnostics from the builtin provisioners that can be annotated
with configuration context and instance addresses.
This is part of a general effort to move all of Terraform's non-library
package surface under internal in order to reinforce that these are for
internal use within Terraform only.
If you were previously importing packages under this prefix into an
external codebase, you could pin to an earlier release tag as an interim
solution until you've make a plan to achieve the same functionality some
other way.
