opentofu/states/instance_object_src.go
Martin Atkins 424afe0ace states: separate types for encoded and decoded state objects
The types here were originally written to allow us to defer decoding of
object values until schemas are available, but it turns out that this was
forcing us to defer decoding longer than necessary and potentially decode
the same value multiple times.

To avoid this, we create pairs of types to represent the encoded and
decoded versions and methods for moving between them. These types are
identical to one another apart from how the dynamic values are
represented.
2018-10-16 18:58:49 -07:00

92 lines
3.7 KiB
Go

package states
import (
"github.com/zclconf/go-cty/cty"
ctyjson "github.com/zclconf/go-cty/cty/json"
"github.com/hashicorp/terraform/addrs"
"github.com/hashicorp/terraform/config/hcl2shim"
)
// ResourceInstanceObjectSrc is a not-fully-decoded version of
// ResourceInstanceObject. Decoding of it can be completed by first handling
// any schema migration steps to get to the latest schema version and then
// calling method Decode with the implied type of the latest schema.
type ResourceInstanceObjectSrc struct {
// SchemaVersion is the resource-type-specific schema version number that
// was current when either AttrsJSON or AttrsFlat was encoded. Migration
// steps are required if this is less than the current version number
// reported by the corresponding provider.
SchemaVersion uint64
// AttrsJSON is a JSON-encoded representation of the object attributes,
// encoding the value (of the object type implied by the associated resource
// type schema) that represents this remote object in Terraform Language
// expressions, and is compared with configuration when producing a diff.
//
// This is retained in JSON format here because it may require preprocessing
// before decoding if, for example, the stored attributes are for an older
// schema version which the provider must upgrade before use. If the
// version is current, it is valid to simply decode this using the
// type implied by the current schema, without the need for the provider
// to perform an upgrade first.
//
// When writing a ResourceInstanceObject into the state, AttrsJSON should
// always be conformant to the current schema version and the current
// schema version should be recorded in the SchemaVersion field.
AttrsJSON []byte
// AttrsFlat is a legacy form of attributes used in older state file
// formats, and in the new state format for objects that haven't yet been
// upgraded. This attribute is mutually exclusive with Attrs: for any
// ResourceInstanceObject, only one of these attributes may be populated
// and the other must be nil.
//
// An instance object with this field populated should be upgraded to use
// Attrs at the earliest opportunity, since this legacy flatmap-based
// format will be phased out over time. AttrsFlat should not be used when
// writing new or updated objects to state; instead, callers must follow
// the recommendations in the AttrsJSON documentation above.
AttrsFlat map[string]string
// These fields all correspond to the fields of the same name on
// ResourceInstanceObject.
Private cty.Value
Status ObjectStatus
Dependencies []addrs.Referenceable
}
// Decode unmarshals the raw representation of the object attributes. Pass the
// implied type of the corresponding resource type schema for correct operation.
//
// Before calling Decode, the caller must check that the SchemaVersion field
// exactly equals the version number of the schema whose implied type is being
// passed, or else the result is undefined.
//
// The returned object may share internal references with the receiver and
// so the caller must not mutate the receiver any further once once this
// method is called.
func (os *ResourceInstanceObjectSrc) Decode(ty cty.Type) (*ResourceInstanceObject, error) {
var val cty.Value
var err error
if os.AttrsFlat != nil {
// Legacy mode. We'll do our best to unpick this from the flatmap.
val, err = hcl2shim.HCL2ValueFromFlatmap(os.AttrsFlat, ty)
if err != nil {
return nil, err
}
} else {
val, err = ctyjson.Unmarshal(os.AttrsJSON, ty)
if err != nil {
return nil, err
}
}
return &ResourceInstanceObject{
Value: val,
Status: os.Status,
Dependencies: os.Dependencies,
Private: os.Private,
}, nil
}