terraform/plans/objchange/compatible.go

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package objchange
import (
"fmt"
"strconv"
"github.com/zclconf/go-cty/cty"
"github.com/zclconf/go-cty/cty/convert"
"github.com/hashicorp/terraform/configs/configschema"
)
// AssertObjectCompatible checks whether the given "actual" value is a valid
// completion of the possibly-partially-unknown "planned" value.
//
// This means that any known leaf value in "planned" must be equal to the
// corresponding value in "actual", and various other similar constraints.
//
// Any inconsistencies are reported by returning a non-zero number of errors.
// These errors are usually (but not necessarily) cty.PathError values
// referring to a particular nested value within the "actual" value.
//
// The two values must have types that conform to the given schema's implied
// type, or this function will panic.
func AssertObjectCompatible(schema *configschema.Block, planned, actual cty.Value) []error {
return assertObjectCompatible(schema, planned, actual, nil)
}
func assertObjectCompatible(schema *configschema.Block, planned, actual cty.Value, path cty.Path) []error {
var errs []error
if planned.IsNull() && !actual.IsNull() {
errs = append(errs, path.NewErrorf("was absent, but now present"))
return errs
}
if actual.IsNull() && !planned.IsNull() {
errs = append(errs, path.NewErrorf("was present, but now absent"))
return errs
}
if planned.IsNull() {
// No further checks possible if both values are null
return errs
}
for name, attrS := range schema.Attributes {
plannedV := planned.GetAttr(name)
actualV := actual.GetAttr(name)
path := append(path, cty.GetAttrStep{Name: name})
moreErrs := assertValueCompatible(plannedV, actualV, path)
if attrS.Sensitive {
if len(moreErrs) > 0 {
// Use a vague placeholder message instead, to avoid disclosing
// sensitive information.
errs = append(errs, path.NewErrorf("inconsistent values for sensitive attribute"))
}
} else {
errs = append(errs, moreErrs...)
}
}
for name, blockS := range schema.BlockTypes {
plannedV := planned.GetAttr(name)
actualV := actual.GetAttr(name)
// As a special case, we permit a "planned" block with exactly one
// element where all of the "leaf" values are unknown, since that's
// what HCL's dynamic block extension generates if the for_each
// expression is itself unknown and thus it cannot predict how many
// child blocks will get created.
switch blockS.Nesting {
case configschema.NestingSingle:
if allLeafValuesUnknown(plannedV) && !plannedV.IsNull() {
return errs
}
case configschema.NestingList, configschema.NestingMap, configschema.NestingSet:
if plannedV.IsKnown() && !plannedV.IsNull() && plannedV.LengthInt() == 1 {
elemVs := plannedV.AsValueSlice()
if allLeafValuesUnknown(elemVs[0]) {
return errs
}
}
default:
panic(fmt.Sprintf("unsupported nesting mode %s", blockS.Nesting))
}
path := append(path, cty.GetAttrStep{Name: name})
switch blockS.Nesting {
case configschema.NestingSingle:
moreErrs := assertObjectCompatible(&blockS.Block, plannedV, actualV, path)
errs = append(errs, moreErrs...)
case configschema.NestingList:
// A NestingList might either be a list or a tuple, depending on
// whether there are dynamically-typed attributes inside. However,
// both support a similar-enough API that we can treat them the
// same for our purposes here.
if !plannedV.IsKnown() || plannedV.IsNull() || actualV.IsNull() {
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continue
}
plannedL := plannedV.LengthInt()
actualL := actualV.LengthInt()
if plannedL != actualL {
errs = append(errs, path.NewErrorf("block count changed from %d to %d", plannedL, actualL))
continue
}
for it := plannedV.ElementIterator(); it.Next(); {
idx, plannedEV := it.Element()
if !actualV.HasIndex(idx).True() {
continue
}
actualEV := actualV.Index(idx)
moreErrs := assertObjectCompatible(&blockS.Block, plannedEV, actualEV, append(path, cty.IndexStep{Key: idx}))
errs = append(errs, moreErrs...)
}
case configschema.NestingMap:
// A NestingMap might either be a map or an object, depending on
// whether there are dynamically-typed attributes inside, but
// that's decided statically and so both values will have the same
// kind.
if plannedV.Type().IsObjectType() {
plannedAtys := plannedV.Type().AttributeTypes()
actualAtys := actualV.Type().AttributeTypes()
for k := range plannedAtys {
if _, ok := actualAtys[k]; !ok {
errs = append(errs, path.NewErrorf("block key %q has vanished", k))
continue
}
plannedEV := plannedV.GetAttr(k)
actualEV := actualV.GetAttr(k)
moreErrs := assertObjectCompatible(&blockS.Block, plannedEV, actualEV, append(path, cty.GetAttrStep{Name: k}))
errs = append(errs, moreErrs...)
}
for k := range actualAtys {
if _, ok := plannedAtys[k]; !ok {
errs = append(errs, path.NewErrorf("new block key %q has appeared", k))
continue
}
}
} else {
if !plannedV.IsKnown() || plannedV.IsNull() || actualV.IsNull() {
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continue
}
plannedL := plannedV.LengthInt()
actualL := actualV.LengthInt()
if plannedL != actualL {
errs = append(errs, path.NewErrorf("block count changed from %d to %d", plannedL, actualL))
continue
}
for it := plannedV.ElementIterator(); it.Next(); {
idx, plannedEV := it.Element()
if !actualV.HasIndex(idx).True() {
continue
}
actualEV := actualV.Index(idx)
moreErrs := assertObjectCompatible(&blockS.Block, plannedEV, actualEV, append(path, cty.IndexStep{Key: idx}))
errs = append(errs, moreErrs...)
}
}
case configschema.NestingSet:
if !plannedV.IsKnown() || plannedV.IsNull() || actualV.IsNull() {
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continue
}
setErrs := assertSetValuesCompatible(plannedV, actualV, path, func(plannedEV, actualEV cty.Value) bool {
errs := assertObjectCompatible(&blockS.Block, plannedEV, actualEV, append(path, cty.IndexStep{Key: actualEV}))
return len(errs) == 0
})
errs = append(errs, setErrs...)
// There can be fewer elements in a set after its elements are all
// known (values that turn out to be equal will coalesce) but the
// number of elements must never get larger.
plannedL := plannedV.LengthInt()
actualL := actualV.LengthInt()
if plannedL < actualL {
errs = append(errs, path.NewErrorf("block set length changed from %d to %d", plannedL, actualL))
}
default:
panic(fmt.Sprintf("unsupported nesting mode %s", blockS.Nesting))
}
}
return errs
}
func assertValueCompatible(planned, actual cty.Value, path cty.Path) []error {
// NOTE: We don't normally use the GoString rendering of cty.Value in
// user-facing error messages as a rule, but we make an exception
// for this function because we expect the user to pass this message on
// verbatim to the provider development team and so more detail is better.
var errs []error
if planned.Type() == cty.DynamicPseudoType {
// Anything goes, then
return errs
}
if problems := planned.Type().TestConformance(actual.Type()); len(problems) > 0 {
errs = append(errs, path.NewErrorf("wrong final value type: %s", convert.MismatchMessage(actual.Type(), planned.Type())))
// If the types don't match then we can't do any other comparisons,
// so we bail early.
return errs
}
if !planned.IsKnown() {
// We didn't know what were going to end up with during plan, so
// anything goes during apply.
return errs
}
if actual.IsNull() {
if planned.IsNull() {
return nil
}
errs = append(errs, path.NewErrorf("was %#v, but now null", planned))
return errs
}
if planned.IsNull() {
errs = append(errs, path.NewErrorf("was null, but now %#v", actual))
return errs
}
ty := planned.Type()
switch {
case !actual.IsKnown():
errs = append(errs, path.NewErrorf("was known, but now unknown"))
case ty.IsPrimitiveType():
if !actual.Equals(planned).True() {
errs = append(errs, path.NewErrorf("was %#v, but now %#v", planned, actual))
}
case ty.IsListType() || ty.IsMapType() || ty.IsTupleType():
for it := planned.ElementIterator(); it.Next(); {
k, plannedV := it.Element()
if !actual.HasIndex(k).True() {
errs = append(errs, path.NewErrorf("element %s has vanished", indexStrForErrors(k)))
continue
}
actualV := actual.Index(k)
moreErrs := assertValueCompatible(plannedV, actualV, append(path, cty.IndexStep{Key: k}))
errs = append(errs, moreErrs...)
}
for it := actual.ElementIterator(); it.Next(); {
k, _ := it.Element()
if !planned.HasIndex(k).True() {
errs = append(errs, path.NewErrorf("new element %s has appeared", indexStrForErrors(k)))
}
}
case ty.IsObjectType():
atys := ty.AttributeTypes()
for name := range atys {
// Because we already tested that the two values have the same type,
// we can assume that the same attributes are present in both and
// focus just on testing their values.
plannedV := planned.GetAttr(name)
actualV := actual.GetAttr(name)
moreErrs := assertValueCompatible(plannedV, actualV, append(path, cty.GetAttrStep{Name: name}))
errs = append(errs, moreErrs...)
}
case ty.IsSetType():
// We can't really do anything useful for sets here because changing
// an unknown element to known changes the identity of the element, and
// so we can't correlate them properly. However, we will at least check
// to ensure that the number of elements is consistent, along with
// the general type-match checks we ran earlier in this function.
if planned.IsKnown() && !planned.IsNull() && !actual.IsNull() {
setErrs := assertSetValuesCompatible(planned, actual, path, func(plannedV, actualV cty.Value) bool {
errs := assertValueCompatible(plannedV, actualV, append(path, cty.IndexStep{Key: actualV}))
return len(errs) == 0
})
errs = append(errs, setErrs...)
// There can be fewer elements in a set after its elements are all
// known (values that turn out to be equal will coalesce) but the
// number of elements must never get larger.
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plannedL := planned.LengthInt()
actualL := actual.LengthInt()
if plannedL < actualL {
errs = append(errs, path.NewErrorf("length changed from %d to %d", plannedL, actualL))
}
}
}
return errs
}
func indexStrForErrors(v cty.Value) string {
switch v.Type() {
case cty.Number:
return v.AsBigFloat().Text('f', -1)
case cty.String:
return strconv.Quote(v.AsString())
default:
// Should be impossible, since no other index types are allowed!
return fmt.Sprintf("%#v", v)
}
}
func allLeafValuesUnknown(v cty.Value) bool {
seenKnownValue := false
cty.Walk(v, func(path cty.Path, cv cty.Value) (bool, error) {
if cv.IsNull() {
seenKnownValue = true
}
if cv.Type().IsPrimitiveType() && cv.IsKnown() {
seenKnownValue = true
}
return true, nil
})
return !seenKnownValue
}
// assertSetValuesCompatible checks that each of the elements in a can
// be correlated with at least one equivalent element in b and vice-versa,
// using the given correlation function.
//
// This allows the number of elements in the sets to change as long as all
// elements in both sets can be correlated, making this function safe to use
// with sets that may contain unknown values as long as the unknown case is
// addressed in some reasonable way in the callback function.
//
// The callback always recieves values from set a as its first argument and
// values from set b in its second argument, so it is safe to use with
// non-commutative functions.
//
// As with assertValueCompatible, we assume that the target audience of error
// messages here is a provider developer (via a bug report from a user) and so
// we intentionally violate our usual rule of keeping cty implementation
// details out of error messages.
func assertSetValuesCompatible(planned, actual cty.Value, path cty.Path, f func(aVal, bVal cty.Value) bool) []error {
a := planned
b := actual
// Our methodology here is a little tricky, to deal with the fact that
// it's impossible to directly correlate two non-equal set elements because
// they don't have identities separate from their values.
// The approach is to count the number of equivalent elements each element
// of a has in b and vice-versa, and then return true only if each element
// in both sets has at least one equivalent.
as := a.AsValueSlice()
bs := b.AsValueSlice()
aeqs := make([]bool, len(as))
beqs := make([]bool, len(bs))
for ai, av := range as {
for bi, bv := range bs {
if f(av, bv) {
aeqs[ai] = true
beqs[bi] = true
}
}
}
var errs []error
for i, eq := range aeqs {
if !eq {
errs = append(errs, path.NewErrorf("planned set element %#v does not correlate with any element in actual", as[i]))
}
}
if len(errs) > 0 {
// Exit early since otherwise we're likely to generate duplicate
// error messages from the other perspective in the subsequent loop.
return errs
}
for i, eq := range beqs {
if !eq {
errs = append(errs, path.NewErrorf("actual set element %#v does not correlate with any element in plan", bs[i]))
}
}
return errs
}