The previous commit added a new flag to schema.Schema which is documented
to make a list with MaxItems: 1 be presented to Terraform Core as a single
value instead, giving a way to switch to non-list nested resources without
it being a breaking change for Terraform v0.11 users as long as it's done
prior to a provider's first v0.12-compatible release.
This is the implementation of that mechanism. It's intentionally
implemented as a suite of extra fixups rather than direct modifications to
existing shim code because we want to ensure that this has no effect
whatsoever on the result of a resource type that _isn't_ using AsSingle.
Although there is some small unit test coverage of the fixup steps here,
the primary testing for this is in the test provider since the integration
of all of these fixup steps in the correct order is the more important
result than any of the intermediate fixup steps.
This makes some slight adjustments to the shape of the schema we
present to Terraform Core without affecting how it is consumed by the
SDK and thus the provider. This mechanism is designed specifically to
avoid changing how the schema is interpreted by the SDK itself or by the
provider, so that prior behavior can be preserved in Terraform v0.11 mode.
This also includes a new rule that Computed-only (i.e. not also Optional)
schemas _always_ map to attributes, because that is a better mapping of
the intent: they are object values to be used in expressions. Nested
blocks conceptually represent nested objects that are in some sense
independent of what they are embedded in, and so they cannot themselves be
computed.
Historically helper/schema did not support non-primitive map attributes
because they cannot be represented unambiguously in flatmap. When we
initially implemented CoreConfigSchema here we mapped that situation to
a nested block of mode NestingMap, even though that'd never worked until
now, assuming that it'd be harmless because providers wouldn't be using
it.
It turns out that some providers are, in fact, incorrectly populating
a TypeMap schema with Elem: &schema.Resource, apparently under the false
assumption that it would constrain the keys allowed in the map. In
practice, helper/schema has just been ignoring this and treating such
attributes as map of string. (#20076)
In order to preserve the behavior of these existing incorrectly-specified
attribute definitions, here we mimic the helper/schema behavior by
presenting as an attribute of type map(string).
These attributes have also been shown in some documentation as nested
blocks (with no equals sign), so that'll need to be fixed in user
configurations as they upgrade to Terraform 0.12. However, the existing
upgrade tool rules will take care of that as a natural consequence of the
name being indicated as an attribute in the schema, rather than as a block
type.
This fixes#20076.
Since the SDK's schema system conflates attributes and nested blocks, it's
possible to state some nonsensical schema situations such as:
- A nested block is both optional but has MinItems > 0
- A nested block is entirely computed but has MinItems or MaxItems set
Both of these weird situations are handled here in the same way that the
existing helper/schema validation code would've handled them: by
effectively disabling the MinItems/MaxItems checks where they would've
been ignored before.
the MinItems/MaxItems
The SDK has a mechanism that effectively makes it possible to declare an
attribute as being _conditionally_ required, which is not a concept that
Terraform Core is aware of.
Since this mechanism is in practice only used for a small UX improvement
in prompting for these values interactively when the environment variable
is not set, we avoid here introducing all of this complexity into the
plugin protocol by just having the provider selectively modify its schema
if it detects that such an attribute might be set dynamically.
This then prevents Terraform Core from validating the presence of the
argument or prompting for a new value for it, allowing the null value to
pass through into the provider so that the default value can be generated
again dynamically.
This is a kinda-kludgey solution which we're accepting here because the
alternative would be a much-more-complex two-pass decode operation within
Core itself, and that doesn't seem worth it.
This fixes#19139.
Resource timeouts were a separate config block, but did not exist in the
resource schema. Insert any defined timeouts when generating the
configshema.Block so that the fields can be accepted and validated by
core.
When converting a legacy schemaMap to a configschema, we need to add
"id" as a required attribute to top-level resources if it's not
declared.
The "id" field will be required to interoperate with the legacy helper
schema, since the presence of an id was used to indicate the existence
of a resource.
The "config" package is no longer used and will be removed as part
of the 0.12 release cleanup. Since configschema is part of the
"new world" of configuration modelling, it makes more sense for
it to live as a subdirectory of the newer "configs" package.
We will need access to this information in order to render interactive
input prompts, and it will also be useful in returning schema information
to external tools such as text editors that have autocomplete-like
functionality.
In order to parse provider, resource and data source configuration from
HCL2 config files, we need to know the relevant configuration schema.
This new method allows Terraform Core to request these from a provider.
This is a breaking change to this interface, so all of its implementers
in this package are updated too. This includes concrete implementations
of the new method in helper/schema that use the schema conversion code
added in an earlier commit to produce a configschema.Block automatically.
Plugins compiled against prior versions of helper/schema will not have
support for this method, and so calls to them will fail. Callers of
this new method will therefore need to sniff for support using the
SchemaAvailable field added to both ResourceType and DataSource.
This careful handling will need to persist until next time we increment
the plugin protocol version, at which point we can make the breaking
change of requiring this information to be available.
We don't currently have any need for this information, but we're
propagating it out of helper/schema here pre-emptively so that once we
later have a use for it we will not need to rebuild the providers to gain
access to it.
The long-term expected use-case for this is to have Terraform Core use
static analysis techniques to trace the path of sensitive data through
interpolations so that intermediate results can be flagged as sensitive
too, but we have a lot more work to do before such a thing would actually
be possible.
As part of moving to the next-generation HCL implementation,
Terraform Core is getting its own representation of configuration schema
that is tailored for configuration-processing use-cases. The capabilities
of this are a subset of the helper/schema model primarily concerned with
the configuration structure and value types, leaving detailed validation
and defaults for helper/schema to still solve.
These new methods allow mechanical creation of a schema in the new Core
schema model from a schema expressed in the helper/schema model. This is
not yet used as of this commit, but will be used later to implement some
new ResourceProvider methods that will allow core to obtain the schema
for provider, resource and data source configuration while remaining
source-compatible with existing provider implementations.
Martin Atkins