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yaml.go
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yaml.go
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// Copyright 2020 VMware, Inc.
// SPDX-License-Identifier: Apache-2.0
package yttlibrary
import (
"fmt"
"carvel.dev/ytt/pkg/template/core"
"carvel.dev/ytt/pkg/yamlmeta"
"github.com/k14s/starlark-go/starlark"
"github.com/k14s/starlark-go/starlarkstruct"
)
var (
// YAMLAPI contains the definition of the @ytt:yaml module
YAMLAPI = starlark.StringDict{
"yaml": &starlarkstruct.Module{
Name: "yaml",
Members: starlark.StringDict{
"encode": starlark.NewBuiltin("yaml.encode", core.ErrWrapper(yamlModule{}.starlarkEncode)),
"decode": starlark.NewBuiltin("yaml.decode", core.ErrWrapper(yamlModule{}.starlarkDecode)),
},
},
}
)
type yamlModule struct{}
// starlarkEncode adapts a call from Starlark to yamlModule.Encode()
func (b yamlModule) starlarkEncode(_ *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, _ []starlark.Tuple) (starlark.Value, error) {
if args.Len() != 1 {
return starlark.None, fmt.Errorf("expected exactly one argument")
}
val, err := core.NewStarlarkValue(args.Index(0)).AsGoValue()
if err != nil {
return starlark.None, err
}
encoded, err := b.Encode(val)
if err != nil {
return starlark.None, nil
}
return starlark.String(encoded), nil
}
// Encode renders the provided input as a YAML-formatted string
func (b yamlModule) Encode(goValue interface{}) (string, error) {
var docSet *yamlmeta.DocumentSet
switch typedVal := goValue.(type) {
case *yamlmeta.DocumentSet:
docSet = typedVal
case *yamlmeta.Document:
// Documents should be part of DocumentSet by the time it makes it here
panic("Unexpected document")
default:
docSet = &yamlmeta.DocumentSet{Items: []*yamlmeta.Document{{Value: typedVal}}}
}
valBs, err := docSet.AsBytes()
if err != nil {
return "", err
}
return string(valBs), nil
}
// Decode is a core.StarlarkFunc that parses the provided input from YAML format into dicts, lists, and scalars
func (b yamlModule) starlarkDecode(_ *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, _ []starlark.Tuple) (starlark.Value, error) {
if args.Len() != 1 {
return starlark.None, fmt.Errorf("expected exactly one argument")
}
valEncoded, err := core.NewStarlarkValue(args.Index(0)).AsString()
if err != nil {
return starlark.None, err
}
value, err := b.Decode(valEncoded)
if err != nil {
return nil, err
}
return value, nil
}
func (b yamlModule) Decode(yamlString string) (starlark.Value, error) {
var decoded interface{}
err := yamlmeta.PlainUnmarshal([]byte(yamlString), &decoded)
if err != nil {
return starlark.None, err
}
value := core.NewGoValue(decoded).AsStarlarkValue()
return value, nil
}