149 lines
4.7 KiB
Go
149 lines
4.7 KiB
Go
// Copyright (C) MongoDB, Inc. 2017-present.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may
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// not use this file except in compliance with the License. You may obtain
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// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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package bsoncodec
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import (
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"reflect"
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"strings"
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)
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// StructTagParser returns the struct tags for a given struct field.
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//
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// Deprecated: Defining custom BSON struct tag parsers will not be supported in Go Driver 2.0.
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type StructTagParser interface {
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ParseStructTags(reflect.StructField) (StructTags, error)
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}
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// StructTagParserFunc is an adapter that allows a generic function to be used
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// as a StructTagParser.
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//
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// Deprecated: Defining custom BSON struct tag parsers will not be supported in Go Driver 2.0.
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type StructTagParserFunc func(reflect.StructField) (StructTags, error)
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// ParseStructTags implements the StructTagParser interface.
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func (stpf StructTagParserFunc) ParseStructTags(sf reflect.StructField) (StructTags, error) {
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return stpf(sf)
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}
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// StructTags represents the struct tag fields that the StructCodec uses during
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// the encoding and decoding process.
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//
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// In the case of a struct, the lowercased field name is used as the key for each exported
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// field but this behavior may be changed using a struct tag. The tag may also contain flags to
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// adjust the marshalling behavior for the field.
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//
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// The properties are defined below:
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//
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// OmitEmpty Only include the field if it's not set to the zero value for the type or to
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// empty slices or maps.
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//
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// MinSize Marshal an integer of a type larger than 32 bits value as an int32, if that's
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// feasible while preserving the numeric value.
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//
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// Truncate When unmarshaling a BSON double, it is permitted to lose precision to fit within
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// a float32.
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//
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// Inline Inline the field, which must be a struct or a map, causing all of its fields
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// or keys to be processed as if they were part of the outer struct. For maps,
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// keys must not conflict with the bson keys of other struct fields.
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//
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// Skip This struct field should be skipped. This is usually denoted by parsing a "-"
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// for the name.
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//
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// Deprecated: Defining custom BSON struct tag parsers will not be supported in Go Driver 2.0.
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type StructTags struct {
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Name string
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OmitEmpty bool
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MinSize bool
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Truncate bool
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Inline bool
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Skip bool
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}
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// DefaultStructTagParser is the StructTagParser used by the StructCodec by default.
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// It will handle the bson struct tag. See the documentation for StructTags to see
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// what each of the returned fields means.
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//
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// If there is no name in the struct tag fields, the struct field name is lowercased.
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// The tag formats accepted are:
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//
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// "[<key>][,<flag1>[,<flag2>]]"
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//
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// `(...) bson:"[<key>][,<flag1>[,<flag2>]]" (...)`
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//
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// An example:
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//
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// type T struct {
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// A bool
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// B int "myb"
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// C string "myc,omitempty"
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// D string `bson:",omitempty" json:"jsonkey"`
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// E int64 ",minsize"
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// F int64 "myf,omitempty,minsize"
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// }
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//
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// A struct tag either consisting entirely of '-' or with a bson key with a
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// value consisting entirely of '-' will return a StructTags with Skip true and
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// the remaining fields will be their default values.
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//
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// Deprecated: DefaultStructTagParser will be removed in Go Driver 2.0.
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var DefaultStructTagParser StructTagParserFunc = func(sf reflect.StructField) (StructTags, error) {
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key := strings.ToLower(sf.Name)
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tag, ok := sf.Tag.Lookup("bson")
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if !ok && !strings.Contains(string(sf.Tag), ":") && len(sf.Tag) > 0 {
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tag = string(sf.Tag)
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}
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return parseTags(key, tag)
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}
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func parseTags(key string, tag string) (StructTags, error) {
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var st StructTags
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if tag == "-" {
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st.Skip = true
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return st, nil
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}
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for idx, str := range strings.Split(tag, ",") {
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if idx == 0 && str != "" {
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key = str
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}
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switch str {
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case "omitempty":
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st.OmitEmpty = true
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case "minsize":
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st.MinSize = true
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case "truncate":
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st.Truncate = true
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case "inline":
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st.Inline = true
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}
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}
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st.Name = key
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return st, nil
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}
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// JSONFallbackStructTagParser has the same behavior as DefaultStructTagParser
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// but will also fallback to parsing the json tag instead on a field where the
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// bson tag isn't available.
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//
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// Deprecated: Use [go.mongodb.org/mongo-driver/bson.Encoder.UseJSONStructTags] and
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// [go.mongodb.org/mongo-driver/bson.Decoder.UseJSONStructTags] instead.
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var JSONFallbackStructTagParser StructTagParserFunc = func(sf reflect.StructField) (StructTags, error) {
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key := strings.ToLower(sf.Name)
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tag, ok := sf.Tag.Lookup("bson")
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if !ok {
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tag, ok = sf.Tag.Lookup("json")
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}
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if !ok && !strings.Contains(string(sf.Tag), ":") && len(sf.Tag) > 0 {
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tag = string(sf.Tag)
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}
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return parseTags(key, tag)
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}
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