32 lines
1.3 KiB
Go
32 lines
1.3 KiB
Go
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package function
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import (
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"github.com/zclconf/go-cty/cty"
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)
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// Unpredictable wraps a given function such that it retains the same arguments
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// and type checking behavior but will return an unknown value when called.
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//
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// It is recommended that most functions be "pure", which is to say that they
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// will always produce the same value given particular input. However,
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// sometimes it is necessary to offer functions whose behavior depends on
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// some external state, such as reading a file or determining the current time.
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// In such cases, an unpredictable wrapper might be used to stand in for
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// the function during some sort of prior "checking" phase in order to delay
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// the actual effect until later.
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//
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// While Unpredictable can support a function that isn't pure in its
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// implementation, it still expects a function to be pure in its type checking
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// behavior, except for the special case of returning cty.DynamicPseudoType
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// if it is not yet able to predict its return value based on current argument
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// information.
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func Unpredictable(f Function) Function {
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newSpec := *f.spec // shallow copy
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newSpec.Impl = unpredictableImpl
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return New(&newSpec)
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}
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func unpredictableImpl(args []cty.Value, retType cty.Type) (cty.Value, error) {
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return cty.UnknownVal(retType), nil
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}
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