mirror of
https://github.com/prometheus/prometheus.git
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320 lines
10 KiB
Go
320 lines
10 KiB
Go
package yaml
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import (
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"bytes"
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"encoding/json"
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"fmt"
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"io"
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"reflect"
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"strconv"
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"gopkg.in/yaml.v2"
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)
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// Marshal marshals the object into JSON then converts JSON to YAML and returns the
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// YAML.
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func Marshal(o interface{}) ([]byte, error) {
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j, err := json.Marshal(o)
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if err != nil {
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return nil, fmt.Errorf("error marshaling into JSON: %v", err)
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}
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y, err := JSONToYAML(j)
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if err != nil {
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return nil, fmt.Errorf("error converting JSON to YAML: %v", err)
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}
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return y, nil
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}
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// JSONOpt is a decoding option for decoding from JSON format.
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type JSONOpt func(*json.Decoder) *json.Decoder
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// Unmarshal converts YAML to JSON then uses JSON to unmarshal into an object,
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// optionally configuring the behavior of the JSON unmarshal.
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func Unmarshal(y []byte, o interface{}, opts ...JSONOpt) error {
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return yamlUnmarshal(y, o, false, opts...)
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}
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// UnmarshalStrict strictly converts YAML to JSON then uses JSON to unmarshal
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// into an object, optionally configuring the behavior of the JSON unmarshal.
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func UnmarshalStrict(y []byte, o interface{}, opts ...JSONOpt) error {
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return yamlUnmarshal(y, o, true, append(opts, DisallowUnknownFields)...)
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}
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// yamlUnmarshal unmarshals the given YAML byte stream into the given interface,
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// optionally performing the unmarshalling strictly
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func yamlUnmarshal(y []byte, o interface{}, strict bool, opts ...JSONOpt) error {
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vo := reflect.ValueOf(o)
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unmarshalFn := yaml.Unmarshal
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if strict {
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unmarshalFn = yaml.UnmarshalStrict
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}
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j, err := yamlToJSON(y, &vo, unmarshalFn)
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if err != nil {
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return fmt.Errorf("error converting YAML to JSON: %v", err)
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}
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err = jsonUnmarshal(bytes.NewReader(j), o, opts...)
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if err != nil {
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return fmt.Errorf("error unmarshaling JSON: %v", err)
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}
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return nil
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}
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// jsonUnmarshal unmarshals the JSON byte stream from the given reader into the
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// object, optionally applying decoder options prior to decoding. We are not
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// using json.Unmarshal directly as we want the chance to pass in non-default
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// options.
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func jsonUnmarshal(r io.Reader, o interface{}, opts ...JSONOpt) error {
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d := json.NewDecoder(r)
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for _, opt := range opts {
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d = opt(d)
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}
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if err := d.Decode(&o); err != nil {
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return fmt.Errorf("while decoding JSON: %v", err)
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}
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return nil
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}
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// JSONToYAML Converts JSON to YAML.
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func JSONToYAML(j []byte) ([]byte, error) {
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// Convert the JSON to an object.
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var jsonObj interface{}
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// We are using yaml.Unmarshal here (instead of json.Unmarshal) because the
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// Go JSON library doesn't try to pick the right number type (int, float,
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// etc.) when unmarshalling to interface{}, it just picks float64
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// universally. go-yaml does go through the effort of picking the right
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// number type, so we can preserve number type throughout this process.
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err := yaml.Unmarshal(j, &jsonObj)
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if err != nil {
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return nil, err
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}
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// Marshal this object into YAML.
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return yaml.Marshal(jsonObj)
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}
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// YAMLToJSON converts YAML to JSON. Since JSON is a subset of YAML,
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// passing JSON through this method should be a no-op.
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//
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// Things YAML can do that are not supported by JSON:
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// * In YAML you can have binary and null keys in your maps. These are invalid
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// in JSON. (int and float keys are converted to strings.)
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// * Binary data in YAML with the !!binary tag is not supported. If you want to
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// use binary data with this library, encode the data as base64 as usual but do
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// not use the !!binary tag in your YAML. This will ensure the original base64
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// encoded data makes it all the way through to the JSON.
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//
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// For strict decoding of YAML, use YAMLToJSONStrict.
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func YAMLToJSON(y []byte) ([]byte, error) {
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return yamlToJSON(y, nil, yaml.Unmarshal)
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}
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// YAMLToJSONStrict is like YAMLToJSON but enables strict YAML decoding,
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// returning an error on any duplicate field names.
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func YAMLToJSONStrict(y []byte) ([]byte, error) {
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return yamlToJSON(y, nil, yaml.UnmarshalStrict)
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}
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func yamlToJSON(y []byte, jsonTarget *reflect.Value, yamlUnmarshal func([]byte, interface{}) error) ([]byte, error) {
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// Convert the YAML to an object.
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var yamlObj interface{}
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err := yamlUnmarshal(y, &yamlObj)
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if err != nil {
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return nil, err
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}
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// YAML objects are not completely compatible with JSON objects (e.g. you
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// can have non-string keys in YAML). So, convert the YAML-compatible object
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// to a JSON-compatible object, failing with an error if irrecoverable
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// incompatibilties happen along the way.
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jsonObj, err := convertToJSONableObject(yamlObj, jsonTarget)
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if err != nil {
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return nil, err
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}
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// Convert this object to JSON and return the data.
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return json.Marshal(jsonObj)
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}
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func convertToJSONableObject(yamlObj interface{}, jsonTarget *reflect.Value) (interface{}, error) {
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var err error
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// Resolve jsonTarget to a concrete value (i.e. not a pointer or an
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// interface). We pass decodingNull as false because we're not actually
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// decoding into the value, we're just checking if the ultimate target is a
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// string.
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if jsonTarget != nil {
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ju, tu, pv := indirect(*jsonTarget, false)
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// We have a JSON or Text Umarshaler at this level, so we can't be trying
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// to decode into a string.
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if ju != nil || tu != nil {
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jsonTarget = nil
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} else {
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jsonTarget = &pv
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}
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}
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// If yamlObj is a number or a boolean, check if jsonTarget is a string -
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// if so, coerce. Else return normal.
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// If yamlObj is a map or array, find the field that each key is
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// unmarshaling to, and when you recurse pass the reflect.Value for that
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// field back into this function.
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switch typedYAMLObj := yamlObj.(type) {
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case map[interface{}]interface{}:
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// JSON does not support arbitrary keys in a map, so we must convert
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// these keys to strings.
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//
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// From my reading of go-yaml v2 (specifically the resolve function),
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// keys can only have the types string, int, int64, float64, binary
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// (unsupported), or null (unsupported).
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strMap := make(map[string]interface{})
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for k, v := range typedYAMLObj {
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// Resolve the key to a string first.
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var keyString string
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switch typedKey := k.(type) {
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case string:
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keyString = typedKey
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case int:
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keyString = strconv.Itoa(typedKey)
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case int64:
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// go-yaml will only return an int64 as a key if the system
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// architecture is 32-bit and the key's value is between 32-bit
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// and 64-bit. Otherwise the key type will simply be int.
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keyString = strconv.FormatInt(typedKey, 10)
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case float64:
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// Stolen from go-yaml to use the same conversion to string as
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// the go-yaml library uses to convert float to string when
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// Marshaling.
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s := strconv.FormatFloat(typedKey, 'g', -1, 32)
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switch s {
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case "+Inf":
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s = ".inf"
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case "-Inf":
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s = "-.inf"
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case "NaN":
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s = ".nan"
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}
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keyString = s
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case bool:
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if typedKey {
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keyString = "true"
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} else {
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keyString = "false"
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}
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default:
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return nil, fmt.Errorf("Unsupported map key of type: %s, key: %+#v, value: %+#v",
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reflect.TypeOf(k), k, v)
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}
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// jsonTarget should be a struct or a map. If it's a struct, find
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// the field it's going to map to and pass its reflect.Value. If
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// it's a map, find the element type of the map and pass the
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// reflect.Value created from that type. If it's neither, just pass
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// nil - JSON conversion will error for us if it's a real issue.
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if jsonTarget != nil {
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t := *jsonTarget
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if t.Kind() == reflect.Struct {
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keyBytes := []byte(keyString)
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// Find the field that the JSON library would use.
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var f *field
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fields := cachedTypeFields(t.Type())
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for i := range fields {
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ff := &fields[i]
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if bytes.Equal(ff.nameBytes, keyBytes) {
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f = ff
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break
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}
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// Do case-insensitive comparison.
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if f == nil && ff.equalFold(ff.nameBytes, keyBytes) {
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f = ff
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}
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}
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if f != nil {
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// Find the reflect.Value of the most preferential
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// struct field.
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jtf := t.Field(f.index[0])
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strMap[keyString], err = convertToJSONableObject(v, &jtf)
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if err != nil {
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return nil, err
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}
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continue
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}
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} else if t.Kind() == reflect.Map {
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// Create a zero value of the map's element type to use as
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// the JSON target.
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jtv := reflect.Zero(t.Type().Elem())
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strMap[keyString], err = convertToJSONableObject(v, &jtv)
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if err != nil {
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return nil, err
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}
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continue
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}
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}
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strMap[keyString], err = convertToJSONableObject(v, nil)
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if err != nil {
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return nil, err
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}
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}
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return strMap, nil
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case []interface{}:
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// We need to recurse into arrays in case there are any
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// map[interface{}]interface{}'s inside and to convert any
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// numbers to strings.
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// If jsonTarget is a slice (which it really should be), find the
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// thing it's going to map to. If it's not a slice, just pass nil
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// - JSON conversion will error for us if it's a real issue.
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var jsonSliceElemValue *reflect.Value
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if jsonTarget != nil {
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t := *jsonTarget
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if t.Kind() == reflect.Slice {
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// By default slices point to nil, but we need a reflect.Value
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// pointing to a value of the slice type, so we create one here.
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ev := reflect.Indirect(reflect.New(t.Type().Elem()))
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jsonSliceElemValue = &ev
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}
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}
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// Make and use a new array.
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arr := make([]interface{}, len(typedYAMLObj))
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for i, v := range typedYAMLObj {
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arr[i], err = convertToJSONableObject(v, jsonSliceElemValue)
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if err != nil {
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return nil, err
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}
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}
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return arr, nil
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default:
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// If the target type is a string and the YAML type is a number,
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// convert the YAML type to a string.
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if jsonTarget != nil && (*jsonTarget).Kind() == reflect.String {
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// Based on my reading of go-yaml, it may return int, int64,
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// float64, or uint64.
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var s string
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switch typedVal := typedYAMLObj.(type) {
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case int:
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s = strconv.FormatInt(int64(typedVal), 10)
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case int64:
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s = strconv.FormatInt(typedVal, 10)
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case float64:
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s = strconv.FormatFloat(typedVal, 'g', -1, 32)
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case uint64:
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s = strconv.FormatUint(typedVal, 10)
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case bool:
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if typedVal {
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s = "true"
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} else {
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s = "false"
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}
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}
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if len(s) > 0 {
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yamlObj = interface{}(s)
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}
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}
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return yamlObj, nil
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}
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}
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