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terraform/plans/objchange/all_null.go

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plans/objchange: Don't presume unknown for values unset in config Previously we would construct a proposed new state with unknown values in place of any not-set-in-config computed attributes, trying to save the provider a little work in specifying that itself. Unfortunately that turns out to be problematic because it conflates two concerns: attributes can be explicitly set in configuration to an unknown value, in which case the final result of that unknown overrides any default value the provider might normally populate. In other words, this allows the provider to recognize in the proposed new state the difference between an Optional+Computed attribute being set to unknown in the config vs not being set in the config at all. The provider now has the responsibility to replace these proposed null values with unknown values during PlanResourceChange if it expects to select a value during the apply step. It may also populate a known value if the final result can be predicted at plan time, as is the case for constant defaults specified in the provider code. This change comes from a realization that from core's perspective the helper/schema ideas of zero values, explicit default values, and customizediff tweaks are all just examples of "defaults", and by allowing the provider to see during plan whether these attributes are being explicitly set in configuration and thus decide whether the default will be provided immediately during plan or deferred until apply.
2019-02-07 23:01:39 +01:00
package objchange
import (
"github.com/hashicorp/terraform/configs/configschema"
"github.com/zclconf/go-cty/cty"
)
// AllAttributesNull constructs a non-null cty.Value of the object type implied
// by the given schema that has all of its leaf attributes set to null and all
// of its nested block collections set to zero-length.
//
// This simulates what would result from decoding an empty configuration block
// with the given schema, except that it does not produce errors
func AllAttributesNull(schema *configschema.Block) cty.Value {
configs/configschema: Introduce the NestingGroup mode for blocks In study of existing providers we've found a pattern we werent previously accounting for of using a nested block type to represent a group of arguments that relate to a particular feature that is always enabled but where it improves configuration readability to group all of its settings together in a nested block. The existing NestingSingle was not a good fit for this because it is designed under the assumption that the presence or absence of the block has some significance in enabling or disabling the relevant feature, and so for these always-active cases we'd generate a misleading plan where the settings for the feature appear totally absent, rather than showing the default values that will be selected. NestingGroup is, therefore, a slight variation of NestingSingle where presence vs. absence of the block is not distinguishable (it's never null) and instead its contents are treated as unset when the block is absent. This then in turn causes any default values associated with the nested arguments to be honored and displayed in the plan whenever the block is not explicitly configured. The current SDK cannot activate this mode, but that's okay because its "legacy type system" opt-out flag allows it to force a block to be processed in this way anyway. We're adding this now so that we can introduce the feature in a future SDK without causing a breaking change to the protocol, since the set of possible block nesting modes is not extensible.
2019-04-09 00:32:53 +02:00
// "All attributes null" happens to be the definition of EmptyValue for
// a Block, so we can just delegate to that.
return schema.EmptyValue()
plans/objchange: Don't presume unknown for values unset in config Previously we would construct a proposed new state with unknown values in place of any not-set-in-config computed attributes, trying to save the provider a little work in specifying that itself. Unfortunately that turns out to be problematic because it conflates two concerns: attributes can be explicitly set in configuration to an unknown value, in which case the final result of that unknown overrides any default value the provider might normally populate. In other words, this allows the provider to recognize in the proposed new state the difference between an Optional+Computed attribute being set to unknown in the config vs not being set in the config at all. The provider now has the responsibility to replace these proposed null values with unknown values during PlanResourceChange if it expects to select a value during the apply step. It may also populate a known value if the final result can be predicted at plan time, as is the case for constant defaults specified in the provider code. This change comes from a realization that from core's perspective the helper/schema ideas of zero values, explicit default values, and customizediff tweaks are all just examples of "defaults", and by allowing the provider to see during plan whether these attributes are being explicitly set in configuration and thus decide whether the default will be provided immediately during plan or deferred until apply.
2019-02-07 23:01:39 +01:00
}