131 lines
3.6 KiB
Go
131 lines
3.6 KiB
Go
package stdlib
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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/zclconf/go-cty/cty/convert"
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"github.com/zclconf/go-cty/cty/function"
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)
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var ConcatFunc = function.New(&function.Spec{
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Params: []function.Parameter{},
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VarParam: &function.Parameter{
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Name: "seqs",
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Type: cty.DynamicPseudoType,
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},
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Type: func(args []cty.Value) (ret cty.Type, err error) {
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if len(args) == 0 {
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return cty.NilType, fmt.Errorf("at least one argument is required")
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}
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if args[0].Type().IsListType() {
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// Possibly we're going to return a list, if all of our other
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// args are also lists and we can find a common element type.
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tys := make([]cty.Type, len(args))
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for i, val := range args {
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ty := val.Type()
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if !ty.IsListType() {
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tys = nil
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break
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}
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tys[i] = ty
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}
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if tys != nil {
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commonType, _ := convert.UnifyUnsafe(tys)
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if commonType != cty.NilType {
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return commonType, nil
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}
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}
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}
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etys := make([]cty.Type, 0, len(args))
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for i, val := range args {
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ety := val.Type()
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switch {
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case ety.IsTupleType():
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etys = append(etys, ety.TupleElementTypes()...)
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case ety.IsListType():
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if !val.IsKnown() {
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// We need to know the list to count its elements to
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// build our tuple type, so any concat of an unknown
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// list can't be typed yet.
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return cty.DynamicPseudoType, nil
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}
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l := val.LengthInt()
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subEty := ety.ElementType()
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for j := 0; j < l; j++ {
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etys = append(etys, subEty)
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}
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default:
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return cty.NilType, function.NewArgErrorf(
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i, "all arguments must be lists or tuples; got %s",
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ety.FriendlyName(),
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)
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}
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}
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return cty.Tuple(etys), nil
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},
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Impl: func(args []cty.Value, retType cty.Type) (ret cty.Value, err error) {
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switch {
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case retType.IsListType():
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// If retType is a list type then we know that all of the
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// given values will be lists and that they will either be of
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// retType or of something we can convert to retType.
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vals := make([]cty.Value, 0, len(args))
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for i, list := range args {
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list, err = convert.Convert(list, retType)
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if err != nil {
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// Conversion might fail because we used UnifyUnsafe
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// to choose our return type.
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return cty.NilVal, function.NewArgError(i, err)
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}
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it := list.ElementIterator()
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for it.Next() {
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_, v := it.Element()
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vals = append(vals, v)
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}
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}
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if len(vals) == 0 {
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return cty.ListValEmpty(retType.ElementType()), nil
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}
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return cty.ListVal(vals), nil
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case retType.IsTupleType():
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// If retType is a tuple type then we could have a mixture of
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// lists and tuples but we know they all have known values
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// (because our params don't AllowUnknown) and we know that
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// concatenating them all together will produce a tuple of
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// retType because of the work we did in the Type function above.
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vals := make([]cty.Value, 0, len(args))
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for _, seq := range args {
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// Both lists and tuples support ElementIterator, so this is easy.
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it := seq.ElementIterator()
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for it.Next() {
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_, v := it.Element()
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vals = append(vals, v)
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}
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}
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return cty.TupleVal(vals), nil
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default:
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// should never happen if Type is working correctly above
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panic("unsupported return type")
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}
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},
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})
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// Concat takes one or more sequences (lists or tuples) and returns the single
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// sequence that results from concatenating them together in order.
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//
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// If all of the given sequences are lists of the same element type then the
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// result is a list of that type. Otherwise, the result is a of a tuple type
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// constructed from the given sequence types.
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func Concat(seqs ...cty.Value) (cty.Value, error) {
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return ConcatFunc.Call(seqs)
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}
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