mirror of
https://github.com/restic/restic.git
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212 lines
6.0 KiB
Go
212 lines
6.0 KiB
Go
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// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package gensupport
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import (
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"encoding/json"
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"fmt"
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"reflect"
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"strings"
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)
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// MarshalJSON returns a JSON encoding of schema containing only selected fields.
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// A field is selected if any of the following is true:
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// * it has a non-empty value
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// * its field name is present in forceSendFields and it is not a nil pointer or nil interface
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// * its field name is present in nullFields.
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// The JSON key for each selected field is taken from the field's json: struct tag.
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func MarshalJSON(schema interface{}, forceSendFields, nullFields []string) ([]byte, error) {
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if len(forceSendFields) == 0 && len(nullFields) == 0 {
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return json.Marshal(schema)
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}
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mustInclude := make(map[string]bool)
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for _, f := range forceSendFields {
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mustInclude[f] = true
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}
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useNull := make(map[string]bool)
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useNullMaps := make(map[string]map[string]bool)
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for _, nf := range nullFields {
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parts := strings.SplitN(nf, ".", 2)
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field := parts[0]
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if len(parts) == 1 {
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useNull[field] = true
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} else {
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if useNullMaps[field] == nil {
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useNullMaps[field] = map[string]bool{}
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}
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useNullMaps[field][parts[1]] = true
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}
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}
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dataMap, err := schemaToMap(schema, mustInclude, useNull, useNullMaps)
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if err != nil {
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return nil, err
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}
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return json.Marshal(dataMap)
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}
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func schemaToMap(schema interface{}, mustInclude, useNull map[string]bool, useNullMaps map[string]map[string]bool) (map[string]interface{}, error) {
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m := make(map[string]interface{})
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s := reflect.ValueOf(schema)
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st := s.Type()
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for i := 0; i < s.NumField(); i++ {
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jsonTag := st.Field(i).Tag.Get("json")
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if jsonTag == "" {
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continue
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}
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tag, err := parseJSONTag(jsonTag)
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if err != nil {
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return nil, err
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}
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if tag.ignore {
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continue
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}
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v := s.Field(i)
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f := st.Field(i)
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if useNull[f.Name] {
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if !isEmptyValue(v) {
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return nil, fmt.Errorf("field %q in NullFields has non-empty value", f.Name)
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}
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m[tag.apiName] = nil
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continue
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}
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if !includeField(v, f, mustInclude) {
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continue
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}
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// If map fields are explicitly set to null, use a map[string]interface{}.
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if f.Type.Kind() == reflect.Map && useNullMaps[f.Name] != nil {
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ms, ok := v.Interface().(map[string]string)
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if !ok {
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return nil, fmt.Errorf("field %q has keys in NullFields but is not a map[string]string", f.Name)
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}
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mi := map[string]interface{}{}
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for k, v := range ms {
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mi[k] = v
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}
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for k := range useNullMaps[f.Name] {
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mi[k] = nil
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}
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m[tag.apiName] = mi
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continue
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}
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// nil maps are treated as empty maps.
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if f.Type.Kind() == reflect.Map && v.IsNil() {
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m[tag.apiName] = map[string]string{}
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continue
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}
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// nil slices are treated as empty slices.
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if f.Type.Kind() == reflect.Slice && v.IsNil() {
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m[tag.apiName] = []bool{}
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continue
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}
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if tag.stringFormat {
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m[tag.apiName] = formatAsString(v, f.Type.Kind())
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} else {
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m[tag.apiName] = v.Interface()
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}
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}
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return m, nil
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}
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// formatAsString returns a string representation of v, dereferencing it first if possible.
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func formatAsString(v reflect.Value, kind reflect.Kind) string {
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if kind == reflect.Ptr && !v.IsNil() {
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v = v.Elem()
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}
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return fmt.Sprintf("%v", v.Interface())
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}
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// jsonTag represents a restricted version of the struct tag format used by encoding/json.
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// It is used to describe the JSON encoding of fields in a Schema struct.
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type jsonTag struct {
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apiName string
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stringFormat bool
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ignore bool
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}
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// parseJSONTag parses a restricted version of the struct tag format used by encoding/json.
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// The format of the tag must match that generated by the Schema.writeSchemaStruct method
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// in the api generator.
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func parseJSONTag(val string) (jsonTag, error) {
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if val == "-" {
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return jsonTag{ignore: true}, nil
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}
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var tag jsonTag
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i := strings.Index(val, ",")
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if i == -1 || val[:i] == "" {
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return tag, fmt.Errorf("malformed json tag: %s", val)
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}
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tag = jsonTag{
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apiName: val[:i],
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}
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switch val[i+1:] {
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case "omitempty":
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case "omitempty,string":
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tag.stringFormat = true
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default:
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return tag, fmt.Errorf("malformed json tag: %s", val)
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}
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return tag, nil
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}
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// Reports whether the struct field "f" with value "v" should be included in JSON output.
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func includeField(v reflect.Value, f reflect.StructField, mustInclude map[string]bool) bool {
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// The regular JSON encoding of a nil pointer is "null", which means "delete this field".
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// Therefore, we could enable field deletion by honoring pointer fields' presence in the mustInclude set.
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// However, many fields are not pointers, so there would be no way to delete these fields.
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// Rather than partially supporting field deletion, we ignore mustInclude for nil pointer fields.
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// Deletion will be handled by a separate mechanism.
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if f.Type.Kind() == reflect.Ptr && v.IsNil() {
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return false
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}
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// The "any" type is represented as an interface{}. If this interface
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// is nil, there is no reasonable representation to send. We ignore
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// these fields, for the same reasons as given above for pointers.
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if f.Type.Kind() == reflect.Interface && v.IsNil() {
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return false
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}
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return mustInclude[f.Name] || !isEmptyValue(v)
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}
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// isEmptyValue reports whether v is the empty value for its type. This
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// implementation is based on that of the encoding/json package, but its
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// correctness does not depend on it being identical. What's important is that
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// this function return false in situations where v should not be sent as part
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// of a PATCH operation.
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func isEmptyValue(v reflect.Value) bool {
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switch v.Kind() {
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case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
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return v.Len() == 0
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case reflect.Bool:
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return !v.Bool()
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return v.Int() == 0
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return v.Uint() == 0
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case reflect.Float32, reflect.Float64:
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return v.Float() == 0
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case reflect.Interface, reflect.Ptr:
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return v.IsNil()
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}
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return false
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}
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