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decoder_spec.go
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decoder_spec.go
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// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0
package configschema
import (
"runtime"
"sync"
"unsafe"
"github.com/hashicorp/hcl/v2/hcldec"
"github.com/zclconf/go-cty/cty"
)
var mapLabelNames = []string{"key"}
// specCache is a global cache of all the generated hcldec.Spec values for
// Blocks. This cache is used by the Block.DecoderSpec method to memoize calls
// and prevent unnecessary regeneration of the spec, especially when they are
// large and deeply nested.
// Caching these externally rather than within the struct is required because
// Blocks are used by value and copied when working with NestedBlocks, and the
// copying of the value prevents any safe synchronisation of the struct itself.
//
// While we are using the *Block pointer as the cache key, and the Block
// contents are mutable, once a Block is created it is treated as immutable for
// the duration of its life. Because a Block is a representation of a logical
// schema, which cannot change while it's being used, any modifications to the
// schema during execution would be an error.
type specCache struct {
sync.Mutex
specs map[uintptr]hcldec.Spec
}
var decoderSpecCache = specCache{
specs: map[uintptr]hcldec.Spec{},
}
// get returns the Spec associated with eth given Block, or nil if non is
// found.
func (s *specCache) get(b *Block) hcldec.Spec {
s.Lock()
defer s.Unlock()
k := uintptr(unsafe.Pointer(b))
return s.specs[k]
}
// set stores the given Spec as being the result of b.DecoderSpec().
func (s *specCache) set(b *Block, spec hcldec.Spec) {
s.Lock()
defer s.Unlock()
// the uintptr value gets us a unique identifier for each block, without
// tying this to the block value itself.
k := uintptr(unsafe.Pointer(b))
if _, ok := s.specs[k]; ok {
return
}
s.specs[k] = spec
// This must use a finalizer tied to the Block, otherwise we'll continue to
// build up Spec values as the Blocks are recycled.
runtime.SetFinalizer(b, s.delete)
}
// delete removes the spec associated with the given Block.
func (s *specCache) delete(b *Block) {
s.Lock()
defer s.Unlock()
k := uintptr(unsafe.Pointer(b))
delete(s.specs, k)
}
// DecoderSpec returns a hcldec.Spec that can be used to decode a HCL Body
// using the facilities in the hcldec package.
//
// The returned specification is guaranteed to return a value of the same type
// returned by method ImpliedType, but it may contain null values if any of the
// block attributes are defined as optional and/or computed respectively.
func (b *Block) DecoderSpec() hcldec.Spec {
ret := hcldec.ObjectSpec{}
if b == nil {
return ret
}
if spec := decoderSpecCache.get(b); spec != nil {
return spec
}
for name, attrS := range b.Attributes {
ret[name] = attrS.decoderSpec(name)
}
for name, blockS := range b.BlockTypes {
if _, exists := ret[name]; exists {
// This indicates an invalid schema, since it's not valid to define
// both an attribute and a block type of the same name. We assume
// that the provider has already used something like
// InternalValidate to validate their schema.
continue
}
childSpec := blockS.Block.DecoderSpec()
switch blockS.Nesting {
case NestingSingle, NestingGroup:
ret[name] = &hcldec.BlockSpec{
TypeName: name,
Nested: childSpec,
Required: blockS.MinItems == 1,
}
if blockS.Nesting == NestingGroup {
ret[name] = &hcldec.DefaultSpec{
Primary: ret[name],
Default: &hcldec.LiteralSpec{
Value: blockS.EmptyValue(),
},
}
}
case NestingList:
// We prefer to use a list where possible, since it makes our
// implied type more complete, but if there are any
// dynamically-typed attributes inside we must use a tuple
// instead, at the expense of our type then not being predictable.
if blockS.Block.specType().HasDynamicTypes() {
ret[name] = &hcldec.BlockTupleSpec{
TypeName: name,
Nested: childSpec,
MinItems: blockS.MinItems,
MaxItems: blockS.MaxItems,
}
} else {
ret[name] = &hcldec.BlockListSpec{
TypeName: name,
Nested: childSpec,
MinItems: blockS.MinItems,
MaxItems: blockS.MaxItems,
}
}
case NestingSet:
// We forbid dynamically-typed attributes inside NestingSet in
// InternalValidate, so we don't do anything special to handle that
// here. (There is no set analog to tuple and object types, because
// cty's set implementation depends on knowing the static type in
// order to properly compute its internal hashes.) We assume that
// the provider has already used something like InternalValidate to
// validate their schema.
ret[name] = &hcldec.BlockSetSpec{
TypeName: name,
Nested: childSpec,
MinItems: blockS.MinItems,
MaxItems: blockS.MaxItems,
}
case NestingMap:
// We prefer to use a list where possible, since it makes our
// implied type more complete, but if there are any
// dynamically-typed attributes inside we must use a tuple
// instead, at the expense of our type then not being predictable.
if blockS.Block.specType().HasDynamicTypes() {
ret[name] = &hcldec.BlockObjectSpec{
TypeName: name,
Nested: childSpec,
LabelNames: mapLabelNames,
}
} else {
ret[name] = &hcldec.BlockMapSpec{
TypeName: name,
Nested: childSpec,
LabelNames: mapLabelNames,
}
}
default:
// Invalid nesting type is just ignored. It's checked by
// InternalValidate. We assume that the provider has already used
// something like InternalValidate to validate their schema.
continue
}
}
decoderSpecCache.set(b, ret)
return ret
}
func (a *Attribute) decoderSpec(name string) hcldec.Spec {
ret := &hcldec.AttrSpec{Name: name}
if a == nil {
return ret
}
if a.NestedType != nil {
if a.Type != cty.NilType {
panic("Invalid attribute schema: NestedType and Type cannot both be set. This is a bug in the provider.")
}
ty := a.NestedType.specType()
ret.Type = ty
ret.Required = a.Required
return ret
}
ret.Type = a.Type
ret.Required = a.Required
return ret
}
// listOptionalAttrsFromObject is a helper function which does *not* recurse
// into NestedType Attributes, because the optional types for each of those will
// belong to their own cty.Object definitions. It is used in other functions
// which themselves handle that recursion.
func listOptionalAttrsFromObject(o *Object) []string {
ret := make([]string, 0)
// This is unlikely to happen outside of tests.
if o == nil {
return ret
}
for name, attr := range o.Attributes {
if attr.Optional || attr.Computed {
ret = append(ret, name)
}
}
return ret
}