341 lines
12 KiB
Go
341 lines
12 KiB
Go
package objchange
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import (
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"fmt"
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"github.com/zclconf/go-cty/cty"
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"github.com/hashicorp/terraform/configs/configschema"
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)
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// ProposedNewObject constructs a proposed new object value by combining the
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// computed attribute values from "prior" with the configured attribute values
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// from "config".
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//
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// Both value must conform to the given schema's implied type, or this function
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// will panic.
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//
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// The prior value must be wholly known, but the config value may be unknown
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// or have nested unknown values.
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//
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// The merging of the two objects includes the attributes of any nested blocks,
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// which will be correlated in a manner appropriate for their nesting mode.
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// Note in particular that the correlation for blocks backed by sets is a
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// heuristic based on matching non-computed attribute values and so it may
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// produce strange results with more "extreme" cases, such as a nested set
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// block where _all_ attributes are computed.
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func ProposedNewObject(schema *configschema.Block, prior, config cty.Value) cty.Value {
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if prior.IsNull() {
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// In this case, we will treat the prior value as unknown so that
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// any computed attributes not overridden in config will show as
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// unknown values, rather than null values.
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prior = cty.UnknownVal(schema.ImpliedType())
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}
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if config.IsNull() || !config.IsKnown() {
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// This is a weird situation, but we'll allow it anyway to free
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// callers from needing to specifically check for these cases.
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return prior
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}
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if (!prior.Type().IsObjectType()) || (!config.Type().IsObjectType()) {
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panic("ProposedNewObject only supports object-typed values")
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}
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// From this point onwards, we can assume that both values are non-null
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// object types, and that the config value itself is known (though it
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// may contain nested values that are unknown.)
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newAttrs := map[string]cty.Value{}
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for name, attr := range schema.Attributes {
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priorV := prior.GetAttr(name)
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configV := config.GetAttr(name)
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var newV cty.Value
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switch {
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case attr.Computed && attr.Optional:
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// This is the trickiest scenario: we want to keep the prior value
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// if the config isn't overriding it. Note that due to some
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// ambiguity here, setting an optional+computed attribute from
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// config and then later switching the config to null in a
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// subsequent change causes the initial config value to be "sticky"
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// unless the provider specifically overrides it during its own
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// plan customization step.
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if configV.IsNull() {
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newV = priorV
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} else {
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newV = configV
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}
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case attr.Computed:
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// configV will always be null in this case, by definition.
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// priorV may also be null, but that's okay.
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newV = priorV
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default:
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// For non-computed attributes, we always take the config value,
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// even if it is null. If it's _required_ then null values
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// should've been caught during an earlier validation step, and
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// so we don't really care about that here.
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newV = configV
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}
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newAttrs[name] = newV
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}
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// Merging nested blocks is a little more complex, since we need to
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// correlate blocks between both objects and then recursively propose
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// a new object for each. The correlation logic depends on the nesting
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// mode for each block type.
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for name, blockType := range schema.BlockTypes {
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priorV := prior.GetAttr(name)
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configV := config.GetAttr(name)
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var newV cty.Value
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switch blockType.Nesting {
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case configschema.NestingSingle:
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newV = ProposedNewObject(&blockType.Block, priorV, configV)
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case configschema.NestingList:
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// Nested blocks are correlated by index.
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if l := configV.LengthInt(); l > 0 {
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newVals := make([]cty.Value, 0, l)
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for it := configV.ElementIterator(); it.Next(); {
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idx, configEV := it.Element()
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if priorV.IsKnown() && (priorV.IsNull() || !priorV.HasIndex(idx).True()) {
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// If there is no corresponding prior element then
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// we just take the config value as-is.
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newVals = append(newVals, configEV)
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continue
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}
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priorEV := priorV.Index(idx)
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newEV := ProposedNewObject(&blockType.Block, priorEV, configEV)
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newVals = append(newVals, newEV)
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}
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// Despite the name, a NestingList might also be a tuple, if
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// its nested schema contains dynamically-typed attributes.
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if configV.Type().IsTupleType() {
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newV = cty.TupleVal(newVals)
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} else {
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newV = cty.ListVal(newVals)
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}
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} else {
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// Despite the name, a NestingList might also be a tuple, if
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// its nested schema contains dynamically-typed attributes.
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if configV.Type().IsTupleType() {
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newV = cty.EmptyTupleVal
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} else {
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newV = cty.ListValEmpty(blockType.ImpliedType())
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}
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}
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case configschema.NestingMap:
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// Despite the name, a NestingMap may produce either a map or
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// object value, depending on whether the nested schema contains
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// dynamically-typed attributes.
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if configV.Type().IsObjectType() {
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// Nested blocks are correlated by key.
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if l := configV.LengthInt(); l > 0 {
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newVals := make(map[string]cty.Value, l)
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atys := configV.Type().AttributeTypes()
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for name := range atys {
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configEV := configV.GetAttr(name)
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if !priorV.Type().HasAttribute(name) {
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// If there is no corresponding prior element then
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// we just take the config value as-is.
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newVals[name] = configEV
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continue
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}
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priorEV := priorV.GetAttr(name)
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newEV := ProposedNewObject(&blockType.Block, priorEV, configEV)
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newVals[name] = newEV
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}
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// Although we call the nesting mode "map", we actually use
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// object values so that elements might have different types
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// in case of dynamically-typed attributes.
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newV = cty.ObjectVal(newVals)
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} else {
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newV = cty.EmptyObjectVal
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}
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} else {
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if l := configV.LengthInt(); l > 0 {
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newVals := make(map[string]cty.Value, l)
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for it := configV.ElementIterator(); it.Next(); {
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idx, configEV := it.Element()
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k := idx.AsString()
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if priorV.IsKnown() && (priorV.IsNull() || !priorV.HasIndex(idx).True()) {
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// If there is no corresponding prior element then
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// we just take the config value as-is.
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newVals[k] = configEV
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continue
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}
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priorEV := priorV.Index(idx)
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newEV := ProposedNewObject(&blockType.Block, priorEV, configEV)
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newVals[k] = newEV
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}
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newV = cty.MapVal(newVals)
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} else {
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newV = cty.MapValEmpty(blockType.ImpliedType())
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}
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}
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case configschema.NestingSet:
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if !configV.Type().IsSetType() {
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panic("configschema.NestingSet value is not a set as expected")
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}
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// Nested blocks are correlated by comparing the element values
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// after eliminating all of the computed attributes. In practice,
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// this means that any config change produces an entirely new
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// nested object, and we only propagate prior computed values
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// if the non-computed attribute values are identical.
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var cmpVals [][2]cty.Value
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if priorV.IsKnown() && !priorV.IsNull() {
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cmpVals = setElementCompareValues(&blockType.Block, priorV, false)
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}
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if l := configV.LengthInt(); l > 0 {
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used := make([]bool, len(cmpVals)) // track used elements in case multiple have the same compare value
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newVals := make([]cty.Value, 0, l)
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for it := configV.ElementIterator(); it.Next(); {
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_, configEV := it.Element()
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var priorEV cty.Value
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for i, cmp := range cmpVals {
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if used[i] {
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continue
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}
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if cmp[1].RawEquals(configEV) {
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priorEV = cmp[0]
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used[i] = true // we can't use this value on a future iteration
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break
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}
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}
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if priorEV == cty.NilVal {
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priorEV = cty.NullVal(blockType.ImpliedType())
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}
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newEV := ProposedNewObject(&blockType.Block, priorEV, configEV)
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newVals = append(newVals, newEV)
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}
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newV = cty.SetVal(newVals)
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} else {
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newV = cty.SetValEmpty(blockType.Block.ImpliedType())
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}
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default:
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// Should never happen, since the above cases are comprehensive.
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panic(fmt.Sprintf("unsupported block nesting mode %s", blockType.Nesting))
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}
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newAttrs[name] = newV
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}
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return cty.ObjectVal(newAttrs)
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}
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// setElementCompareValues takes a known, non-null value of a cty.Set type and
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// returns a table -- constructed of two-element arrays -- that maps original
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// set element values to corresponding values that have all of the computed
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// values removed, making them suitable for comparison with values obtained
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// from configuration. The element type of the set must conform to the implied
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// type of the given schema, or this function will panic.
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//
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// In the resulting slice, the zeroth element of each array is the original
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// value and the one-indexed element is the corresponding "compare value".
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//
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// This is intended to help correlate prior elements with configured elements
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// in ProposedNewObject. The result is a heuristic rather than an exact science,
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// since e.g. two separate elements may reduce to the same value through this
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// process. The caller must therefore be ready to deal with duplicates.
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func setElementCompareValues(schema *configschema.Block, set cty.Value, isConfig bool) [][2]cty.Value {
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ret := make([][2]cty.Value, 0, set.LengthInt())
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for it := set.ElementIterator(); it.Next(); {
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_, ev := it.Element()
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ret = append(ret, [2]cty.Value{ev, setElementCompareValue(schema, ev, isConfig)})
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}
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return ret
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}
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// setElementCompareValue creates a new value that has all of the same
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// non-computed attribute values as the one given but has all computed
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// attribute values forced to null.
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//
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// If isConfig is true then non-null Optional+Computed attribute values will
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// be preserved. Otherwise, they will also be set to null.
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//
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// The input value must conform to the schema's implied type, and the return
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// value is guaranteed to conform to it.
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func setElementCompareValue(schema *configschema.Block, v cty.Value, isConfig bool) cty.Value {
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if v.IsNull() || !v.IsKnown() {
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return v
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}
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attrs := map[string]cty.Value{}
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for name, attr := range schema.Attributes {
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switch {
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case attr.Computed && attr.Optional:
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if isConfig {
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attrs[name] = v.GetAttr(name)
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} else {
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attrs[name] = cty.NullVal(attr.Type)
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}
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case attr.Computed:
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attrs[name] = cty.NullVal(attr.Type)
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default:
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attrs[name] = v.GetAttr(name)
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}
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}
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for name, blockType := range schema.BlockTypes {
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switch blockType.Nesting {
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case configschema.NestingSingle:
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attrs[name] = setElementCompareValue(&blockType.Block, v.GetAttr(name), isConfig)
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case configschema.NestingList, configschema.NestingSet:
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cv := v.GetAttr(name)
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if cv.IsNull() || !cv.IsKnown() {
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attrs[name] = cv
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continue
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}
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if l := cv.LengthInt(); l > 0 {
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elems := make([]cty.Value, 0, l)
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for it := cv.ElementIterator(); it.Next(); {
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_, ev := it.Element()
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elems = append(elems, setElementCompareValue(&blockType.Block, ev, isConfig))
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}
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if blockType.Nesting == configschema.NestingSet {
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// SetValEmpty would panic if given elements that are not
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// all of the same type, but that's guaranteed not to
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// happen here because our input value was _already_ a
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// set and we've not changed the types of any elements here.
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attrs[name] = cty.SetVal(elems)
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} else {
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attrs[name] = cty.TupleVal(elems)
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}
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} else {
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if blockType.Nesting == configschema.NestingSet {
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attrs[name] = cty.SetValEmpty(blockType.Block.ImpliedType())
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} else {
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attrs[name] = cty.EmptyTupleVal
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}
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}
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case configschema.NestingMap:
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cv := v.GetAttr(name)
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if cv.IsNull() || !cv.IsKnown() {
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attrs[name] = cv
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continue
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}
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elems := make(map[string]cty.Value)
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for it := cv.ElementIterator(); it.Next(); {
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kv, ev := it.Element()
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elems[kv.AsString()] = setElementCompareValue(&blockType.Block, ev, isConfig)
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}
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attrs[name] = cty.ObjectVal(elems)
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default:
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// Should never happen, since the above cases are comprehensive.
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panic(fmt.Sprintf("unsupported block nesting mode %s", blockType.Nesting))
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}
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}
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return cty.ObjectVal(attrs)
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}
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