package json

import "github.com/go-json-experiment/json/v1"

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

Migrating to v2

This package (i.e., encoding/json) is now formally known as the v1 package since a v2 package now exists at encoding/json/v2. All the behavior of the v1 package is implemented in terms of the v2 package with the appropriate set of options specified that preserve the historical behavior of v1.

The jsonv2.Marshal function is the newer equivalent of v1 Marshal. The jsonv2.Unmarshal function is the newer equivalent of v1 Unmarshal. The v2 functions have the same calling signature as the v1 equivalent except that they take in variadic Options arguments that can be specified to alter the behavior of marshal or unmarshal. Both v1 and v2 generally behave in similar ways, but there are some notable differences.

The following is a list of differences between v1 and v2:

As mentioned, the entirety of v1 is implemented in terms of v2, where options are implicitly specified to opt into legacy behavior. For example, Marshal directly calls jsonv2.Marshal with DefaultOptionsV1. Similarly, Unmarshal directly calls jsonv2.Unmarshal with DefaultOptionsV1. The DefaultOptionsV1 option represents the set of all options that specify default v1 behavior.

For many of the behavior differences, there are Go struct field options that the author of a Go type can specify to control the behavior such that the type is represented identically in JSON under either v1 or v2 semantics.

The availability of DefaultOptionsV1 and jsonv2.DefaultOptionsV2, where later options take precedence over former options allows for a gradual migration from v1 to v2. For example:

All new usages of "json" in Go should use the v2 package, but the v1 package will forever remain supported.

Example (CustomMarshalJSON)

Code:play  

package main

import (
	"fmt"
	"log"
	"strings"

	"github.com/go-json-experiment/json/v1"
)

type Animal int

const (
	Unknown Animal = iota
	Gopher
	Zebra
)

func (a *Animal) UnmarshalJSON(b []byte) error {
	var s string
	if err := json.Unmarshal(b, &s); err != nil {
		return err
	}
	switch strings.ToLower(s) {
	default:
		*a = Unknown
	case "gopher":
		*a = Gopher
	case "zebra":
		*a = Zebra
	}

	return nil
}

func (a Animal) MarshalJSON() ([]byte, error) {
	var s string
	switch a {
	default:
		s = "unknown"
	case Gopher:
		s = "gopher"
	case Zebra:
		s = "zebra"
	}

	return json.Marshal(s)
}

func main() {
	blob := `["gopher","armadillo","zebra","unknown","gopher","bee","gopher","zebra"]`
	var zoo []Animal
	if err := json.Unmarshal([]byte(blob), &zoo); err != nil {
		log.Fatal(err)
	}

	census := make(map[Animal]int)
	for _, animal := range zoo {
		census[animal] += 1
	}

	fmt.Printf("Zoo Census:\n* Gophers: %d\n* Zebras:  %d\n* Unknown: %d\n",
		census[Gopher], census[Zebra], census[Unknown])

}

Output:

Zoo Census:
* Gophers: 3
* Zebras:  2
* Unknown: 3
Example (TextMarshalJSON)

Code:play  

package main

import (
	"fmt"
	"log"
	"strings"

	"github.com/go-json-experiment/json/v1"
)

type Size int

const (
	Unrecognized Size = iota
	Small
	Large
)

func (s *Size) UnmarshalText(text []byte) error {
	switch strings.ToLower(string(text)) {
	default:
		*s = Unrecognized
	case "small":
		*s = Small
	case "large":
		*s = Large
	}
	return nil
}

func (s Size) MarshalText() ([]byte, error) {
	var name string
	switch s {
	default:
		name = "unrecognized"
	case Small:
		name = "small"
	case Large:
		name = "large"
	}
	return []byte(name), nil
}

func main() {
	blob := `["small","regular","large","unrecognized","small","normal","small","large"]`
	var inventory []Size
	if err := json.Unmarshal([]byte(blob), &inventory); err != nil {
		log.Fatal(err)
	}

	counts := make(map[Size]int)
	for _, size := range inventory {
		counts[size] += 1
	}

	fmt.Printf("Inventory Counts:\n* Small:        %d\n* Large:        %d\n* Unrecognized: %d\n",
		counts[Small], counts[Large], counts[Unrecognized])

}

Output:

Inventory Counts:
* Small:        3
* Large:        2
* Unrecognized: 3

Index

Examples

Functions

func Compact 

func Compact(dst *bytes.Buffer, src []byte) error

Compact appends to dst the JSON-encoded src with insignificant space characters elided.

func HTMLEscape 

func HTMLEscape(dst *bytes.Buffer, src []byte)

HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029 characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029 so that the JSON will be safe to embed inside HTML <script> tags. For historical reasons, web browsers don't honor standard HTML escaping within <script> tags, so an alternative JSON encoding must be used.

Example

Code: 

{
	var out bytes.Buffer
	json.HTMLEscape(&out, []byte(`{"Name":"<b>HTML content</b>"}`))
	out.WriteTo(os.Stdout)
	// Output:
	//{"Name":"\u003cb\u003eHTML content\u003c/b\u003e"}
}

Output:

{"Name":"\u003cb\u003eHTML content\u003c/b\u003e"}

func Indent 

func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error

Indent appends to dst an indented form of the JSON-encoded src. Each element in a JSON object or array begins on a new, indented line beginning with prefix followed by one or more copies of indent according to the indentation nesting. The data appended to dst does not begin with the prefix nor any indentation, to make it easier to embed inside other formatted JSON data. Although leading space characters (space, tab, carriage return, newline) at the beginning of src are dropped, trailing space characters at the end of src are preserved and copied to dst. For example, if src has no trailing spaces, neither will dst; if src ends in a trailing newline, so will dst.

Example

Code: 

{
	type Road struct {
		Name   string
		Number int
	}
	roads := []Road{
		{"Diamond Fork", 29},
		{"Sheep Creek", 51},
	}

	b, err := json.Marshal(roads)
	if err != nil {
		log.Fatal(err)
	}

	var out bytes.Buffer
	json.Indent(&out, b, "=", "\t")
	out.WriteTo(os.Stdout)
	// Output:
	// [
	// =	{
	// =		"Name": "Diamond Fork",
	// =		"Number": 29
	// =	},
	// =	{
	// =		"Name": "Sheep Creek",
	// =		"Number": 51
	// =	}
	// =]
}

Output:

[
=	{
=		"Name": "Diamond Fork",
=		"Number": 29
=	},
=	{
=		"Name": "Sheep Creek",
=		"Number": 51
=	}
=]

func Marshal 

func Marshal(v any) ([]byte, error)

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:

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.

Example

Code: 

{
	type ColorGroup struct {
		ID     int
		Name   string
		Colors []string
	}
	group := ColorGroup{
		ID:     1,
		Name:   "Reds",
		Colors: []string{"Crimson", "Red", "Ruby", "Maroon"},
	}
	b, err := json.Marshal(group)
	if err != nil {
		fmt.Println("error:", err)
	}
	os.Stdout.Write(b)
	// Output:
	// {"ID":1,"Name":"Reds","Colors":["Crimson","Red","Ruby","Maroon"]}
}

Output:

{"ID":1,"Name":"Reds","Colors":["Crimson","Red","Ruby","Maroon"]}

func MarshalIndent 

func MarshalIndent(v any, prefix, indent string) ([]byte, error)

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.

Example

Code: 

{
	data := map[string]int{
		"a": 1,
		"b": 2,
	}

	b, err := json.MarshalIndent(data, "<prefix>", "<indent>")
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println(string(b))
	// Output:
	// {
	// <prefix><indent>"a": 1,
	// <prefix><indent>"b": 2
	// <prefix>}
}

Output:

{
<prefix><indent>"a": 1,
<prefix><indent>"b": 2
<prefix>}

func Unmarshal 

func Unmarshal(data []byte, v any) error

Unmarshal parses the JSON-encoded data and stores the result in the value pointed to by v. If v is nil or not a pointer, Unmarshal returns an InvalidUnmarshalError.

Unmarshal uses the inverse of the encodings that Marshal uses, allocating maps, slices, and pointers as necessary, with the following additional rules:

To unmarshal JSON into a pointer, Unmarshal first handles the case of the JSON being the JSON literal null. In that case, Unmarshal sets the pointer to nil. Otherwise, Unmarshal unmarshals the JSON into the value pointed at by the pointer. If the pointer is nil, Unmarshal allocates a new value for it to point to.

To unmarshal JSON into a value implementing Unmarshaler, Unmarshal calls that value's [Unmarshaler.UnmarshalJSON] method, including when the input is a JSON null. Otherwise, if the value implements encoding.TextUnmarshaler and the input is a JSON quoted string, Unmarshal calls encoding.TextUnmarshaler.UnmarshalText with the unquoted form of the string.

To unmarshal JSON into a struct, Unmarshal matches incoming object keys to the keys used by Marshal (either the struct field name or its tag), preferring an exact match but also accepting a case-insensitive match. By default, object keys which don't have a corresponding struct field are ignored (see Decoder.DisallowUnknownFields for an alternative).

To unmarshal JSON into an interface value, Unmarshal stores one of these in the interface value:

To unmarshal a JSON array into a slice, Unmarshal resets the slice length to zero and then appends each element to the slice. As a special case, to unmarshal an empty JSON array into a slice, Unmarshal replaces the slice with a new empty slice.

To unmarshal a JSON array into a Go array, Unmarshal decodes JSON array elements into corresponding Go array elements. If the Go array is smaller than the JSON array, the additional JSON array elements are discarded. If the JSON array is smaller than the Go array, the additional Go array elements are set to zero values.

To unmarshal a JSON object into a map, Unmarshal first establishes a map to use. If the map is nil, Unmarshal allocates a new map. Otherwise Unmarshal reuses the existing map, keeping existing entries. Unmarshal then stores key-value pairs from the JSON object into the map. The map's key type must either be any string type, an integer, or implement encoding.TextUnmarshaler.

If the JSON-encoded data contain a syntax error, Unmarshal returns a SyntaxError.

If a JSON value is not appropriate for a given target type, or if a JSON number overflows the target type, Unmarshal skips that field and completes the unmarshaling as best it can. If no more serious errors are encountered, Unmarshal returns an UnmarshalTypeError describing the earliest such error. In any case, it's not guaranteed that all the remaining fields following the problematic one will be unmarshaled into the target object.

The JSON null value unmarshals into an interface, map, pointer, or slice by setting that Go value to nil. Because null is often used in JSON to mean “not present,” unmarshaling a JSON null into any other Go type has no effect on the value and produces no error.

When unmarshaling quoted strings, invalid UTF-8 or invalid UTF-16 surrogate pairs are not treated as an error. Instead, they are replaced by the Unicode replacement character U+FFFD.

Example

Code: 

{
	var jsonBlob = []byte(`[
	{"Name": "Platypus", "Order": "Monotremata"},
	{"Name": "Quoll",    "Order": "Dasyuromorphia"}
]`)
	type Animal struct {
		Name  string
		Order string
	}
	var animals []Animal
	err := json.Unmarshal(jsonBlob, &animals)
	if err != nil {
		fmt.Println("error:", err)
	}
	fmt.Printf("%+v", animals)
	// Output:
	// [{Name:Platypus Order:Monotremata} {Name:Quoll Order:Dasyuromorphia}]
}

Output:

[{Name:Platypus Order:Monotremata} {Name:Quoll Order:Dasyuromorphia}]

func Valid 

func Valid(data []byte) bool

Valid reports whether data is a valid JSON encoding.

Example

Code: 

{
	goodJSON := `{"example": 1}`
	badJSON := `{"example":2:]}}`

	fmt.Println(json.Valid([]byte(goodJSON)), json.Valid([]byte(badJSON)))
	// Output:
	// true false
}

Output:

true false

Types

type Decoder 

type Decoder struct {
	// contains filtered or unexported fields
}

A Decoder reads and decodes JSON values from an input stream.

Example

This example uses a Decoder to decode a stream of distinct JSON values.

Code: 

{
	const jsonStream = `
	{"Name": "Ed", "Text": "Knock knock."}
	{"Name": "Sam", "Text": "Who's there?"}
	{"Name": "Ed", "Text": "Go fmt."}
	{"Name": "Sam", "Text": "Go fmt who?"}
	{"Name": "Ed", "Text": "Go fmt yourself!"}
`
	type Message struct {
		Name, Text string
	}
	dec := json.NewDecoder(strings.NewReader(jsonStream))
	for {
		var m Message
		if err := dec.Decode(&m); err == io.EOF {
			break
		} else if err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%s: %s\n", m.Name, m.Text)
	}
	// Output:
	// Ed: Knock knock.
	// Sam: Who's there?
	// Ed: Go fmt.
	// Sam: Go fmt who?
	// Ed: Go fmt yourself!
}

Output:

Ed: Knock knock.
Sam: Who's there?
Ed: Go fmt.
Sam: Go fmt who?
Ed: Go fmt yourself!

func NewDecoder 

func NewDecoder(r io.Reader) *Decoder

NewDecoder returns a new decoder that reads from r.

The decoder introduces its own buffering and may read data from r beyond the JSON values requested.

func (*Decoder) Buffered 

func (dec *Decoder) Buffered() io.Reader

Buffered returns a reader of the data remaining in the Decoder's buffer. The reader is valid until the next call to Decoder.Decode.

func (*Decoder) Decode 

func (dec *Decoder) Decode(v any) error

Decode reads the next JSON-encoded value from its input and stores it in the value pointed to by v.

See the documentation for Unmarshal for details about the conversion of JSON into a Go value.

Example (Stream)

This example uses a Decoder to decode a streaming array of JSON objects.

Code: 

{
	const jsonStream = `
	[
		{"Name": "Ed", "Text": "Knock knock."},
		{"Name": "Sam", "Text": "Who's there?"},
		{"Name": "Ed", "Text": "Go fmt."},
		{"Name": "Sam", "Text": "Go fmt who?"},
		{"Name": "Ed", "Text": "Go fmt yourself!"}
	]
`
	type Message struct {
		Name, Text string
	}
	dec := json.NewDecoder(strings.NewReader(jsonStream))

	// read open bracket
	t, err := dec.Token()
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("%T: %v\n", t, t)

	// while the array contains values
	for dec.More() {
		var m Message
		// decode an array value (Message)
		err := dec.Decode(&m)
		if err != nil {
			log.Fatal(err)
		}

		fmt.Printf("%v: %v\n", m.Name, m.Text)
	}

	// read closing bracket
	t, err = dec.Token()
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("%T: %v\n", t, t)

	// Output:
	// json.Delim: [
	// Ed: Knock knock.
	// Sam: Who's there?
	// Ed: Go fmt.
	// Sam: Go fmt who?
	// Ed: Go fmt yourself!
	// json.Delim: ]
}

Output:

json.Delim: [
Ed: Knock knock.
Sam: Who's there?
Ed: Go fmt.
Sam: Go fmt who?
Ed: Go fmt yourself!
json.Delim: ]

func (*Decoder) DisallowUnknownFields 

func (dec *Decoder) DisallowUnknownFields()

DisallowUnknownFields causes the Decoder to return an error when the destination is a struct and the input contains object keys which do not match any non-ignored, exported fields in the destination.

func (*Decoder) InputOffset 

func (dec *Decoder) InputOffset() int64

InputOffset returns the input stream byte offset of the current decoder position. The offset gives the location of the end of the most recently returned token and the beginning of the next token.

func (*Decoder) More 

func (dec *Decoder) More() bool

More reports whether there is another element in the current array or object being parsed.

func (*Decoder) Token 

func (dec *Decoder) Token() (Token, error)

Token returns the next JSON token in the input stream. At the end of the input stream, Token returns nil, io.EOF.

Token guarantees that the delimiters [ ] { } it returns are properly nested and matched: if Token encounters an unexpected delimiter in the input, it will return an error.

The input stream consists of basic JSON values—bool, string, number, and null—along with delimiters [ ] { } of type Delim to mark the start and end of arrays and objects. Commas and colons are elided.

Example

This example uses a Decoder to decode a stream of distinct JSON values.

Code: 

{
	const jsonStream = `
	{"Message": "Hello", "Array": [1, 2, 3], "Null": null, "Number": 1.234}
`
	dec := json.NewDecoder(strings.NewReader(jsonStream))
	for {
		t, err := dec.Token()
		if err == io.EOF {
			break
		}
		if err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%T: %v", t, t)
		if dec.More() {
			fmt.Printf(" (more)")
		}
		fmt.Printf("\n")
	}
	// Output:
	// json.Delim: { (more)
	// string: Message (more)
	// string: Hello (more)
	// string: Array (more)
	// json.Delim: [ (more)
	// float64: 1 (more)
	// float64: 2 (more)
	// float64: 3
	// json.Delim: ] (more)
	// string: Null (more)
	// <nil>: <nil> (more)
	// string: Number (more)
	// float64: 1.234
	// json.Delim: }
}

Output:

json.Delim: { (more)
string: Message (more)
string: Hello (more)
string: Array (more)
json.Delim: [ (more)
float64: 1 (more)
float64: 2 (more)
float64: 3
json.Delim: ] (more)
string: Null (more)
<nil>: <nil> (more)
string: Number (more)
float64: 1.234
json.Delim: }

func (*Decoder) UseNumber 

func (dec *Decoder) UseNumber()

UseNumber causes the Decoder to unmarshal a number into an interface value as a Number instead of as a float64.

type Delim 

type Delim rune

A Delim is a JSON array or object delimiter, one of [ ] { or }.

func (Delim) String 

func (d Delim) String() string

type Encoder 

type Encoder struct {
	// contains filtered or unexported fields
}

An Encoder writes JSON values to an output stream.

func NewEncoder 

func NewEncoder(w io.Writer) *Encoder

NewEncoder returns a new encoder that writes to w.

func (*Encoder) Encode 

func (enc *Encoder) Encode(v any) error

Encode writes the JSON encoding of v to the stream, followed by a newline character.

See the documentation for Marshal for details about the conversion of Go values to JSON.

func (*Encoder) SetEscapeHTML 

func (enc *Encoder) SetEscapeHTML(on bool)

SetEscapeHTML specifies whether problematic HTML characters should be escaped inside JSON quoted strings. The default behavior is to escape &, <, and > to \u0026, \u003c, and \u003e to avoid certain safety problems that can arise when embedding JSON in HTML.

In non-HTML settings where the escaping interferes with the readability of the output, SetEscapeHTML(false) disables this behavior.

func (*Encoder) SetIndent 

func (enc *Encoder) SetIndent(prefix, indent string)

SetIndent instructs the encoder to format each subsequent encoded value as if indented by the package-level function Indent(dst, src, prefix, indent). Calling SetIndent("", "") disables indentation.

type InvalidUTF8Error 

type InvalidUTF8Error struct {
	S string // the whole string value that caused the error
}

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.

func (*InvalidUTF8Error) Error 

func (e *InvalidUTF8Error) Error() string

type InvalidUnmarshalError 

type InvalidUnmarshalError struct {
	Type reflect.Type
}

An InvalidUnmarshalError describes an invalid argument passed to Unmarshal. (The argument to Unmarshal must be a non-nil pointer.)

func (*InvalidUnmarshalError) Error 

func (e *InvalidUnmarshalError) Error() string

type Marshaler 

type Marshaler = jsonv2.Marshaler

Marshaler is the interface implemented by types that can marshal themselves into valid JSON.

type MarshalerError 

type MarshalerError struct {
	Type reflect.Type
	Err  error
	// contains filtered or unexported fields
}

A MarshalerError represents an error from calling a [Marshaler.MarshalJSON] or encoding.TextMarshaler.MarshalText method.

func (*MarshalerError) Error 

func (e *MarshalerError) Error() string

func (*MarshalerError) Unwrap 

func (e *MarshalerError) Unwrap() error

Unwrap returns the underlying error.

type Number 

type Number string

A Number represents a JSON number literal.

func (Number) Float64 

func (n Number) Float64() (float64, error)

Float64 returns the number as a float64.

func (Number) Int64 

func (n Number) Int64() (int64, error)

Int64 returns the number as an int64.

func (Number) MarshalJSONTo 

func (n Number) MarshalJSONTo(enc *jsontext.Encoder) error

MarshalJSONTo implements jsonv2.MarshalerTo.

func (Number) String 

func (n Number) String() string

String returns the literal text of the number.

func (*Number) UnmarshalJSONFrom 

func (n *Number) UnmarshalJSONFrom(dec *jsontext.Decoder) error

UnmarshalJSONFrom implements jsonv2.UnmarshalerFrom.

type Options 

type Options = jsonopts.Options

Options are a set of options to configure the v2 "json" package to operate with v1 semantics for particular features. Values of this type can be passed to v2 functions like jsonv2.Marshal or jsonv2.Unmarshal. Instead of referencing this type, use jsonv2.Options.

See the "Migrating to v2" section for guidance on how to migrate usage of "json" from using v1 to using v2 instead.

func CallMethodsWithLegacySemantics 

func CallMethodsWithLegacySemantics(v bool) Options

CallMethodsWithLegacySemantics specifies that calling of type-provided marshal and unmarshal methods follow legacy semantics:

This affects either marshaling or unmarshaling. The v1 default is true.

func DefaultOptionsV1 

func DefaultOptionsV1() Options

DefaultOptionsV1 is the full set of all options that define v1 semantics. It is equivalent to the following boolean options being set to true:

All other boolean options are set to false. All non-boolean options are set to the zero value, except for jsontext.WithIndent, which defaults to "\t".

The Marshal and Unmarshal functions in this package are semantically identical to calling the v2 equivalents with this option: 

jsonv2.Marshal(v, jsonv1.DefaultOptionsV1())
jsonv2.Unmarshal(b, v, jsonv1.DefaultOptionsV1())

func EscapeInvalidUTF8 

func EscapeInvalidUTF8(v bool) Options

EscapeInvalidUTF8 specifies that when encoding a jsontext.String with bytes of invalid UTF-8, such bytes are escaped as a hexadecimal Unicode codepoint (i.e., \ufffd). In contrast, the v2 default is to use the minimal representation, which is to encode invalid UTF-8 as the Unicode replacement rune itself (without any form of escaping).

This only affects encoding and is ignored when decoding. The v1 default is true.

func FormatBytesWithLegacySemantics 

func FormatBytesWithLegacySemantics(v bool) Options

FormatBytesWithLegacySemantics specifies that handling of []~byte and [N]~byte types follow legacy semantics:

This affects either marshaling or unmarshaling. The v1 default is true.

func FormatTimeWithLegacySemantics 

func FormatTimeWithLegacySemantics(v bool) Options

FormatTimeWithLegacySemantics specifies that time types are formatted with legacy semantics:

This affects either marshaling or unmarshaling. The v1 default is true.

func MatchCaseSensitiveDelimiter 

func MatchCaseSensitiveDelimiter(v bool) Options

MatchCaseSensitiveDelimiter specifies that underscores and dashes are not to be ignored when performing case-insensitive name matching which occurs under jsonv2.MatchCaseInsensitiveNames or the `case:ignore` tag option. Thus, case-insensitive name matching is identical to strings.EqualFold. Use of this option diminishes the ability of case-insensitive matching to be able to match common case variants (e.g, "foo_bar" with "fooBar").

This affects either marshaling or unmarshaling. The v1 default is true.

func MergeWithLegacySemantics 

func MergeWithLegacySemantics(v bool) Options

MergeWithLegacySemantics specifies that unmarshaling into a non-zero Go value follows legacy semantics:

This only affects unmarshaling and is ignored when marshaling. The v1 default is true.

func OmitEmptyWithLegacyDefinition 

func OmitEmptyWithLegacyDefinition(v bool) Options

OmitEmptyWithLegacyDefinition specifies that the `omitempty` tag option follows a definition of empty where a field is omitted if the Go value is false, 0, a nil pointer, a nil interface value, or any empty array, slice, map, or string. This overrides the v2 semantic where a field is empty if the value marshals as a JSON null or an empty JSON string, object, or array.

The v1 and v2 definitions of `omitempty` are practically the same for Go strings, slices, arrays, and maps. Usages of `omitempty` on Go bools, ints, uints floats, pointers, and interfaces should migrate to use the `omitzero` tag option, which omits a field if it is the zero Go value.

This only affects marshaling and is ignored when unmarshaling. The v1 default is true.

func ReportErrorsWithLegacySemantics 

func ReportErrorsWithLegacySemantics(v bool) Options

ReportErrorsWithLegacySemantics specifies that Marshal and Unmarshal should report errors with legacy semantics:

This affects either marshaling or unmarshaling. The v1 default is true.

func StringifyWithLegacySemantics 

func StringifyWithLegacySemantics(v bool) Options

StringifyWithLegacySemantics specifies that the `string` tag option may stringify bools and string values. It only takes effect on fields where the top-level type is a bool, string, numeric kind, or a pointer to such a kind. Specifically, `string` will not stringify bool, string, or numeric kinds within a composite data type (e.g., array, slice, struct, map, or interface).

When marshaling, such Go values are serialized as their usual JSON representation, but quoted within a JSON string. When unmarshaling, such Go values must be deserialized from a JSON string containing their usual JSON representation. A JSON null quoted in a JSON string is a valid substitute for JSON null while unmarshaling into a Go value that `string` takes effect on.

This affects either marshaling or unmarshaling. The v1 default is true.

func UnmarshalArrayFromAnyLength 

func UnmarshalArrayFromAnyLength(v bool) Options

UnmarshalArrayFromAnyLength specifies that Go arrays can be unmarshaled from input JSON arrays of any length. If the JSON array is too short, then the remaining Go array elements are zeroed. If the JSON array is too long, then the excess JSON array elements are skipped over.

This only affects unmarshaling and is ignored when marshaling. The v1 default is true.

type RawMessage 

type RawMessage = jsontext.Value

RawMessage is a raw encoded JSON value. It implements Marshaler and Unmarshaler and can be used to delay JSON decoding or precompute a JSON encoding.

Example (Marshal)

This example uses RawMessage to use a precomputed JSON during marshal.

Code: 

{
	h := json.RawMessage(`{"precomputed": true}`)

	c := struct {
		Header *json.RawMessage `json:"header"`
		Body   string           `json:"body"`
	}{Header: &h, Body: "Hello Gophers!"}

	b, err := json.MarshalIndent(&c, "", "\t")
	if err != nil {
		fmt.Println("error:", err)
	}
	os.Stdout.Write(b)

	// Output:
	// {
	// 	"header": {
	// 		"precomputed": true
	// 	},
	// 	"body": "Hello Gophers!"
	// }
}

Output:

{
	"header": {
		"precomputed": true
	},
	"body": "Hello Gophers!"
}
Example (Unmarshal)

This example uses RawMessage to delay parsing part of a JSON message.

Code: 

{
	type Color struct {
		Space string
		Point json.RawMessage // delay parsing until we know the color space
	}
	type RGB struct {
		R uint8
		G uint8
		B uint8
	}
	type YCbCr struct {
		Y  uint8
		Cb int8
		Cr int8
	}

	var j = []byte(`[
	{"Space": "YCbCr", "Point": {"Y": 255, "Cb": 0, "Cr": -10}},
	{"Space": "RGB",   "Point": {"R": 98, "G": 218, "B": 255}}
]`)
	var colors []Color
	err := json.Unmarshal(j, &colors)
	if err != nil {
		log.Fatalln("error:", err)
	}

	for _, c := range colors {
		var dst any
		switch c.Space {
		case "RGB":
			dst = new(RGB)
		case "YCbCr":
			dst = new(YCbCr)
		}
		err := json.Unmarshal(c.Point, dst)
		if err != nil {
			log.Fatalln("error:", err)
		}
		fmt.Println(c.Space, dst)
	}
	// Output:
	// YCbCr &{255 0 -10}
	// RGB &{98 218 255}
}

Output:

YCbCr &{255 0 -10}
RGB &{98 218 255}

type SyntaxError 

type SyntaxError struct {
	Offset int64 // error occurred after reading Offset bytes
	// contains filtered or unexported fields
}

A SyntaxError is a description of a JSON syntax error. Unmarshal will return a SyntaxError if the JSON can't be parsed.

func (*SyntaxError) Error 

func (e *SyntaxError) Error() string

type Token 

type Token any

A Token holds a value of one of these types:

type UnmarshalFieldError 

type UnmarshalFieldError struct {
	Key   string
	Type  reflect.Type
	Field reflect.StructField
}

An UnmarshalFieldError describes a JSON object key that led to an unexported (and therefore unwritable) struct field.

Deprecated: No longer used; kept for compatibility.

func (*UnmarshalFieldError) Error 

func (e *UnmarshalFieldError) Error() string

type UnmarshalTypeError 

type UnmarshalTypeError struct {
	Value  string       // description of JSON value - "bool", "array", "number -5"
	Type   reflect.Type // type of Go value it could not be assigned to
	Offset int64        // error occurred after reading Offset bytes
	Struct string       // name of the root type containing the field
	Field  string       // the full path from root node to the value
	Err    error        // may be nil
}

An UnmarshalTypeError describes a JSON value that was not appropriate for a value of a specific Go type.

func (*UnmarshalTypeError) Error 

func (e *UnmarshalTypeError) Error() string

func (*UnmarshalTypeError) Unwrap 

func (e *UnmarshalTypeError) Unwrap() error

type Unmarshaler 

type Unmarshaler = jsonv2.Unmarshaler

Unmarshaler is the interface implemented by types that can unmarshal a JSON description of themselves. The input can be assumed to be a valid encoding of a JSON value. UnmarshalJSON must copy the JSON data if it wishes to retain the data after returning.

type UnsupportedTypeError 

type UnsupportedTypeError struct {
	Type reflect.Type
}

An UnsupportedTypeError is returned by Marshal when attempting to encode an unsupported value type.

func (*UnsupportedTypeError) Error 

func (e *UnsupportedTypeError) Error() string

type UnsupportedValueError 

type UnsupportedValueError struct {
	Value reflect.Value
	Str   string
}

An UnsupportedValueError is returned by Marshal when attempting to encode an unsupported value.

func (*UnsupportedValueError) Error 

func (e *UnsupportedValueError) Error() string

Source Files

decode.go encode.go indent.go inject.go options.go scanner.go stream.go

Version
v0.0.0-20250223041408-d3c622f1b874 (latest)
Published
Feb 23, 2025
Platform
linux/amd64
Imports
15 packages
Last checked
1 month ago –

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