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Diffstat (limited to 'src/encoding/json/v2_encode.go')
| -rw-r--r-- | src/encoding/json/v2_encode.go | 240 |
1 files changed, 240 insertions, 0 deletions
diff --git a/src/encoding/json/v2_encode.go b/src/encoding/json/v2_encode.go new file mode 100644 index 0000000000..c8f35d4281 --- /dev/null +++ b/src/encoding/json/v2_encode.go @@ -0,0 +1,240 @@ +// Copyright 2010 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build goexperiment.jsonv2 + +// Package json implements encoding and decoding of JSON as defined in +// RFC 7159. The mapping between JSON and Go values is described +// in the documentation for the Marshal and Unmarshal functions. +// +// See "JSON and Go" for an introduction to this package: +// https://golang.org/doc/articles/json_and_go.html +package json + +import ( + "reflect" + "strconv" + + jsonv2 "encoding/json/v2" +) + +// Marshal returns the JSON encoding of v. +// +// Marshal traverses the value v recursively. +// If an encountered value implements [Marshaler] +// and is not a nil pointer, Marshal calls [Marshaler.MarshalJSON] +// to produce JSON. If no [Marshaler.MarshalJSON] method is present but the +// value implements [encoding.TextMarshaler] instead, Marshal calls +// [encoding.TextMarshaler.MarshalText] and encodes the result as a JSON string. +// The nil pointer exception is not strictly necessary +// but mimics a similar, necessary exception in the behavior of +// [Unmarshaler.UnmarshalJSON]. +// +// Otherwise, Marshal uses the following type-dependent default encodings: +// +// Boolean values encode as JSON booleans. +// +// Floating point, integer, and [Number] values encode as JSON numbers. +// NaN and +/-Inf values will return an [UnsupportedValueError]. +// +// String values encode as JSON strings coerced to valid UTF-8, +// replacing invalid bytes with the Unicode replacement rune. +// So that the JSON will be safe to embed inside HTML <script> tags, +// the string is encoded using [HTMLEscape], +// which replaces "<", ">", "&", U+2028, and U+2029 are escaped +// to "\u003c","\u003e", "\u0026", "\u2028", and "\u2029". +// This replacement can be disabled when using an [Encoder], +// by calling [Encoder.SetEscapeHTML](false). +// +// Array and slice values encode as JSON arrays, except that +// []byte encodes as a base64-encoded string, and a nil slice +// encodes as the null JSON value. +// +// Struct values encode as JSON objects. +// Each exported struct field becomes a member of the object, using the +// field name as the object key, unless the field is omitted for one of the +// reasons given below. +// +// The encoding of each struct field can be customized by the format string +// stored under the "json" key in the struct field's tag. +// The format string gives the name of the field, possibly followed by a +// comma-separated list of options. The name may be empty in order to +// specify options without overriding the default field name. +// +// The "omitempty" option specifies that the field should be omitted +// from the encoding if the field has an empty value, defined as +// false, 0, a nil pointer, a nil interface value, and any array, +// slice, map, or string of length zero. +// +// As a special case, if the field tag is "-", the field is always omitted. +// Note that a field with name "-" can still be generated using the tag "-,". +// +// Examples of struct field tags and their meanings: +// +// // Field appears in JSON as key "myName". +// Field int `json:"myName"` +// +// // Field appears in JSON as key "myName" and +// // the field is omitted from the object if its value is empty, +// // as defined above. +// Field int `json:"myName,omitempty"` +// +// // Field appears in JSON as key "Field" (the default), but +// // the field is skipped if empty. +// // Note the leading comma. +// Field int `json:",omitempty"` +// +// // Field is ignored by this package. +// Field int `json:"-"` +// +// // Field appears in JSON as key "-". +// Field int `json:"-,"` +// +// The "omitzero" option specifies that the field should be omitted +// from the encoding if the field has a zero value, according to rules: +// +// 1) If the field type has an "IsZero() bool" method, that will be used to +// determine whether the value is zero. +// +// 2) Otherwise, the value is zero if it is the zero value for its type. +// +// If both "omitempty" and "omitzero" are specified, the field will be omitted +// if the value is either empty or zero (or both). +// +// The "string" option signals that a field is stored as JSON inside a +// JSON-encoded string. It applies only to fields of string, floating point, +// integer, or boolean types. This extra level of encoding is sometimes used +// when communicating with JavaScript programs: +// +// Int64String int64 `json:",string"` +// +// The key name will be used if it's a non-empty string consisting of +// only Unicode letters, digits, and ASCII punctuation except quotation +// marks, backslash, and comma. +// +// Embedded struct fields are usually marshaled as if their inner exported fields +// were fields in the outer struct, subject to the usual Go visibility rules amended +// as described in the next paragraph. +// An anonymous struct field with a name given in its JSON tag is treated as +// having that name, rather than being anonymous. +// An anonymous struct field of interface type is treated the same as having +// that type as its name, rather than being anonymous. +// +// The Go visibility rules for struct fields are amended for JSON when +// deciding which field to marshal or unmarshal. If there are +// multiple fields at the same level, and that level is the least +// nested (and would therefore be the nesting level selected by the +// usual Go rules), the following extra rules apply: +// +// 1) Of those fields, if any are JSON-tagged, only tagged fields are considered, +// even if there are multiple untagged fields that would otherwise conflict. +// +// 2) If there is exactly one field (tagged or not according to the first rule), that is selected. +// +// 3) Otherwise there are multiple fields, and all are ignored; no error occurs. +// +// Handling of anonymous struct fields is new in Go 1.1. +// Prior to Go 1.1, anonymous struct fields were ignored. To force ignoring of +// an anonymous struct field in both current and earlier versions, give the field +// a JSON tag of "-". +// +// Map values encode as JSON objects. The map's key type must either be a +// string, an integer type, or implement [encoding.TextMarshaler]. The map keys +// are sorted and used as JSON object keys by applying the following rules, +// subject to the UTF-8 coercion described for string values above: +// - keys of any string type are used directly +// - keys that implement [encoding.TextMarshaler] are marshaled +// - integer keys are converted to strings +// +// Pointer values encode as the value pointed to. +// A nil pointer encodes as the null JSON value. +// +// Interface values encode as the value contained in the interface. +// A nil interface value encodes as the null JSON value. +// +// Channel, complex, and function values cannot be encoded in JSON. +// Attempting to encode such a value causes Marshal to return +// an [UnsupportedTypeError]. +// +// JSON cannot represent cyclic data structures and Marshal does not +// handle them. Passing cyclic structures to Marshal will result in +// an error. +func Marshal(v any) ([]byte, error) { + return jsonv2.Marshal(v, DefaultOptionsV1()) +} + +// MarshalIndent is like [Marshal] but applies [Indent] to format the output. +// Each JSON element in the output will begin on a new line beginning with prefix +// followed by one or more copies of indent according to the indentation nesting. +func MarshalIndent(v any, prefix, indent string) ([]byte, error) { + b, err := Marshal(v) + if err != nil { + return nil, err + } + b, err = appendIndent(nil, b, prefix, indent) + if err != nil { + return nil, err + } + return b, nil +} + +// Marshaler is the interface implemented by types that +// can marshal themselves into valid JSON. +type Marshaler = jsonv2.Marshaler + +// An UnsupportedTypeError is returned by [Marshal] when attempting +// to encode an unsupported value type. +type UnsupportedTypeError struct { + Type reflect.Type +} + +func (e *UnsupportedTypeError) Error() string { + return "json: unsupported type: " + e.Type.String() +} + +// An UnsupportedValueError is returned by [Marshal] when attempting +// to encode an unsupported value. +type UnsupportedValueError struct { + Value reflect.Value + Str string +} + +func (e *UnsupportedValueError) Error() string { + return "json: unsupported value: " + e.Str +} + +// Before Go 1.2, an InvalidUTF8Error was returned by [Marshal] when +// attempting to encode a string value with invalid UTF-8 sequences. +// As of Go 1.2, [Marshal] instead coerces the string to valid UTF-8 by +// replacing invalid bytes with the Unicode replacement rune U+FFFD. +// +// Deprecated: No longer used; kept for compatibility. +type InvalidUTF8Error struct { + S string // the whole string value that caused the error +} + +func (e *InvalidUTF8Error) Error() string { + return "json: invalid UTF-8 in string: " + strconv.Quote(e.S) +} + +// A MarshalerError represents an error from calling a +// [Marshaler.MarshalJSON] or [encoding.TextMarshaler.MarshalText] method. +type MarshalerError struct { + Type reflect.Type + Err error + sourceFunc string +} + +func (e *MarshalerError) Error() string { + srcFunc := e.sourceFunc + if srcFunc == "" { + srcFunc = "MarshalJSON" + } + return "json: error calling " + srcFunc + + " for type " + e.Type.String() + + ": " + e.Err.Error() +} + +// Unwrap returns the underlying error. +func (e *MarshalerError) Unwrap() error { return e.Err } |