terraform/plans/objchange/normalize_obj.go

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package objchange
import (
"github.com/hashicorp/terraform/configs/configschema"
"github.com/zclconf/go-cty/cty"
)
// NormalizeObjectFromLegacySDK takes an object that may have been generated
// by the legacy Terraform SDK (i.e. returned from a provider with the
// LegacyTypeSystem opt-out set) and does its best to normalize it for the
// assumptions we would normally enforce if the provider had not opted out.
//
// In particular, this function guarantees that a value representing a nested
// block will never itself be unknown or null, instead representing that as
// a non-null value that may contain null/unknown values.
//
// The input value must still conform to the implied type of the given schema,
// or else this function may produce garbage results or panic. This is usually
// okay because type consistency is enforced when deserializing the value
// returned from the provider over the RPC wire protocol anyway.
func NormalizeObjectFromLegacySDK(val cty.Value, schema *configschema.Block) cty.Value {
if val == cty.NilVal || val.IsNull() {
// This should never happen in reasonable use, but we'll allow it
// and normalize to a null of the expected type rather than panicking
// below.
return cty.NullVal(schema.ImpliedType())
}
vals := make(map[string]cty.Value)
for name := range schema.Attributes {
// No normalization for attributes, since them being type-conformant
// is all that we require.
vals[name] = val.GetAttr(name)
}
for name, blockS := range schema.BlockTypes {
lv := val.GetAttr(name)
switch blockS.Nesting {
case configschema.NestingSingle:
if lv.IsKnown() {
vals[name] = NormalizeObjectFromLegacySDK(lv, &blockS.Block)
} else {
vals[name] = unknownBlockStub(&blockS.Block)
}
case configschema.NestingList:
switch {
case !lv.IsKnown():
vals[name] = cty.ListVal([]cty.Value{unknownBlockStub(&blockS.Block)})
case lv.IsNull() || lv.LengthInt() == 0:
vals[name] = cty.ListValEmpty(blockS.Block.ImpliedType())
default:
subVals := make([]cty.Value, 0, lv.LengthInt())
for it := lv.ElementIterator(); it.Next(); {
_, subVal := it.Element()
subVals = append(subVals, NormalizeObjectFromLegacySDK(subVal, &blockS.Block))
}
vals[name] = cty.ListVal(subVals)
}
case configschema.NestingSet:
switch {
case !lv.IsKnown():
vals[name] = cty.SetVal([]cty.Value{unknownBlockStub(&blockS.Block)})
case lv.IsNull() || lv.LengthInt() == 0:
vals[name] = cty.SetValEmpty(blockS.Block.ImpliedType())
default:
subVals := make([]cty.Value, 0, lv.LengthInt())
for it := lv.ElementIterator(); it.Next(); {
_, subVal := it.Element()
subVals = append(subVals, NormalizeObjectFromLegacySDK(subVal, &blockS.Block))
}
vals[name] = cty.SetVal(subVals)
}
default:
// The legacy SDK doesn't support NestingMap, so we just assume
// maps are always okay. (If not, we would've detected and returned
// an error to the user before we got here.)
vals[name] = lv
}
}
return cty.ObjectVal(vals)
}
// unknownBlockStub constructs an object value that approximates an unknown
// block by producing a known block object with all of its leaf attribute
// values set to unknown.
//
// Blocks themselves cannot be unknown, so if the legacy SDK tries to return
// such a thing, we'll use this result instead. This convention mimics how
// the dynamic block feature deals with being asked to iterate over an unknown
// value, because our value-checking functions already accept this convention
// as a special case.
func unknownBlockStub(schema *configschema.Block) cty.Value {
vals := make(map[string]cty.Value)
for name, attrS := range schema.Attributes {
vals[name] = cty.UnknownVal(attrS.Type)
}
for name, blockS := range schema.BlockTypes {
switch blockS.Nesting {
case configschema.NestingSingle:
vals[name] = unknownBlockStub(&blockS.Block)
case configschema.NestingList:
// In principle we may be expected to produce a tuple value here,
// if there are any dynamically-typed attributes in our nested block,
// but the legacy SDK doesn't support that, so we just assume it'll
// never be necessary to normalize those. (Incorrect usage in any
// other SDK would be caught and returned as an error before we
// get here.)
vals[name] = cty.ListVal([]cty.Value{unknownBlockStub(&blockS.Block)})
case configschema.NestingSet:
vals[name] = cty.SetVal([]cty.Value{unknownBlockStub(&blockS.Block)})
case configschema.NestingMap:
// A nesting map can never be unknown since we then wouldn't know
// what the keys are. (Legacy SDK doesn't support NestingMap anyway,
// so this should never arise.)
vals[name] = cty.MapValEmpty(blockS.Block.ImpliedType())
}
}
return cty.ObjectVal(vals)
}