Package json
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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
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
func Marshal
func Marshal(v any) ([]byte, error)
Marshal returns the JSON encoding of v.
Marshal traverses the value v recursively.
The input value is encoded as JSON according the following rules:
If the value type implements jsonv2.MarshalerTo, then the MarshalJSONTo method is called to encode the value. If the method returns errors.ErrUnsupported, then the input is encoded according to subsequent rules.
If the value type implements Marshaler, then the MarshalJSON method is called to encode the value.
If the value type implements encoding.TextAppender, then the AppendText method is called to encode the value and subsequently encode its result as a JSON string.
If the value type implements encoding.TextMarshaler, then the MarshalText method is called to encode the value and subsequently encode its result as a JSON string.
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. JSON names containing commas or quotes, or names identical to "" or "-", can be specified using a single-quoted string literal, where the syntax is identical to the Go grammar for a double-quoted string literal, but instead uses single quotes as the delimiters.
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.
▸ Example
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
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.
The JSON input is decoded according the following rules:
If the value type implements jsonv2.UnmarshalerFrom, then the UnmarshalJSONFrom method is called to decode the JSON value. If the method returns errors.ErrUnsupported, then the input is decoded according to subsequent rules.
If the value type implements Unmarshaler, then the UnmarshalJSON method is called to decode the JSON value, including when the input is a JSON null.
If the value implements encoding.TextUnmarshaler and the input is a JSON string, then the UnmarshalText method is called with the unquoted form of the string.
Otherwise, Unmarshal uses the following type-dependent default decodings:
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:
- bool, for JSON booleans
- float64, for JSON numbers
- string, for JSON strings
- []any, for JSON arrays
- map[string]any, for JSON objects
- nil for JSON null
To unmarshal a JSON array into a slice, Unmarshal decodes each JSON array element into the corresponding slice element, reusing existing slice elements in-place. The slice grows to accommodate additional elements, or is truncated if the JSON array is shorter. 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
func Valid 1.9
func Valid(data []byte) bool
Valid reports whether data is a valid JSON encoding.
▸ Example
type Decoder
A Decoder reads and decodes JSON values from an input stream.
type Decoder struct {
// contains filtered or unexported fields
}
▸ Example
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 1.1
func (dec *Decoder) Buffered() io.Reader
Buffered returns a reader of the data remaining in the unread buffer, which may contain zero or more bytes. This is the data already consumed from the input io.Reader, but not yet read by a Decoder.Decode or Decoder.Token call. It may contain bytes that do not form valid JSON as it has not yet been validated according to the JSON grammar. The exact amount of buffered data is an implementation detail of the Decoder and may change over time.
It is the caller's responsibility to concatenate this buffer with the remainder of the input Reader to obtain the full sequence of bytes after the last decoded JSON value.
The reader is valid until the next call to Decoder.Decode or Decoder.Token.
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)
func (*Decoder) DisallowUnknownFields 1.10
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 1.14
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 1.5
func (dec *Decoder) More() bool
More reports whether there is another element in the current array or object being parsed.
func (*Decoder) Token 1.5
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
func (*Decoder) UseNumber 1.1
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 1.5
A Delim is a JSON array or object delimiter, one of [ ] { or }.
type Delim rune
func (Delim) String 1.5
func (d Delim) String() string
type Encoder
An Encoder writes JSON values to an output stream.
type Encoder struct {
// contains filtered or unexported fields
}
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 1.7
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 1.7
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
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 (*InvalidUTF8Error) Error
func (e *InvalidUTF8Error) Error() string
type InvalidUnmarshalError
An InvalidUnmarshalError describes an invalid argument passed to Unmarshal. (The argument to Unmarshal must be a non-nil pointer.)
type InvalidUnmarshalError struct {
Type reflect.Type
}
func (*InvalidUnmarshalError) Error
func (e *InvalidUnmarshalError) Error() string
type Marshaler
Marshaler is the interface implemented by types that can marshal themselves into valid JSON.
type Marshaler = jsonv2.Marshaler
type MarshalerError
A MarshalerError represents an error from calling a [Marshaler.MarshalJSON] or encoding.TextMarshaler.MarshalText method.
type MarshalerError struct {
Type reflect.Type
Err error
// contains filtered or unexported fields
}
func (*MarshalerError) Error
func (e *MarshalerError) Error() string
func (*MarshalerError) Unwrap 1.13
func (e *MarshalerError) Unwrap() error
Unwrap returns the underlying error.
type Number 1.1
A Number represents a JSON number literal.
type Number string
func (Number) Float64 1.1
func (n Number) Float64() (float64, error)
Float64 returns the number as a float64.
func (Number) Int64 1.1
func (n Number) Int64() (int64, error)
Int64 returns the number as an int64.
func (Number) MarshalJSONTo 1.27
func (n Number) MarshalJSONTo(enc *jsontext.Encoder) error
MarshalJSONTo implements jsonv2.MarshalerTo.
func (Number) String 1.1
func (n Number) String() string
String returns the literal text of the number.
func (*Number) UnmarshalJSONFrom 1.27
func (n *Number) UnmarshalJSONFrom(dec *jsontext.Decoder) error
UnmarshalJSONFrom implements jsonv2.UnmarshalerFrom.
type Options 1.27
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.
type Options = jsonopts.Options
func CallMethodsWithLegacySemantics 1.27
func CallMethodsWithLegacySemantics(v bool) Options
CallMethodsWithLegacySemantics specifies that calling of type-provided marshal and unmarshal methods follow legacy semantics:
When marshaling, a marshal method declared on a pointer receiver is only called if the Go value is addressable. Values obtained from an interface or map element are not addressable. Values obtained from a pointer or slice element are addressable. Values obtained from an array element or struct field inherit the addressability of the parent. In contrast, the v2 semantic is to always call marshal methods regardless of addressability.
When marshaling or unmarshaling, the Marshaler or Unmarshaler methods are ignored for map keys. However, encoding.TextMarshaler or encoding.TextUnmarshaler are still callable. In contrast, the v2 semantic is to serialize map keys like any other value (with regard to calling methods), which may include calling Marshaler or Unmarshaler methods, where it is the implementation's responsibility to represent the Go value as a JSON string (as required for JSON object names).
When marshaling, if a map key value implements a marshal method and is a nil pointer, then it is serialized as an empty JSON string. In contrast, the v2 semantic is to report an error.
When marshaling, if an interface type implements a marshal method and the interface value is a nil pointer to a concrete type, then the marshal method is always called. In contrast, the v2 semantic is to never directly call methods on interface values and to instead defer evaluation based upon the underlying concrete value. Similar to non-interface values, marshal methods are not called on nil pointers and are instead serialized as a JSON null.
This affects either marshaling or unmarshaling. The v1 default is true.
func DefaultOptionsV1 1.27
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:
- CallMethodsWithLegacySemantics
- FormatByteArrayAsArray
- FormatBytesWithLegacySemantics
- FormatDurationAsNano
- MatchCaseSensitiveDelimiter
- MergeWithLegacySemantics
- OmitEmptyWithLegacySemantics
- ParseBytesWithLooseRFC4648
- ParseTimeWithLooseRFC3339
- ReportErrorsWithLegacySemantics
- StringifyWithLegacySemantics
- UnmarshalArrayFromAnyLength
- jsonv2.Deterministic
- jsonv2.FormatNilMapAsNull
- jsonv2.FormatNilSliceAsNull
- jsonv2.MatchCaseInsensitiveNames
- jsontext.AllowDuplicateNames
- jsontext.AllowInvalidUTF8
- jsontext.EscapeForHTML
- jsontext.EscapeForJS
- jsontext.PreserveRawStrings
All other options are not present.
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 FormatByteArrayAsArray 1.27
func FormatByteArrayAsArray(v bool) Options
FormatByteArrayAsArray specifies that a Go [N]byte is formatted as a normal Go array in contrast to the v2 default of formatting [N]byte as using binary data encoding (RFC 4648).
This affects either marshaling or unmarshaling. The v1 default is true.
func FormatBytesWithLegacySemantics 1.27
func FormatBytesWithLegacySemantics(v bool) Options
FormatBytesWithLegacySemantics specifies that handling of []~byte and [N]~byte types follow legacy semantics:
A Go []~byte is to be treated as using some form of binary data encoding (RFC 4648) in contrast to the v2 default of only treating []byte as such. In particular, v2 does not treat slices of named byte types as representing binary data.
When marshaling, if a named byte implements a marshal method, then the slice is serialized as a JSON array of elements, each of which call the marshal method.
When unmarshaling, if the input is a JSON array, then unmarshal into the []~byte as if it were a normal Go slice. In contrast, the v2 default is to report an error unmarshaling a JSON array when expecting some form of binary data encoding.
This affects either marshaling or unmarshaling. The v1 default is true.
func FormatDurationAsNano 1.27
func FormatDurationAsNano(v bool) Options
FormatDurationAsNano specifies that a time.Duration is formatted as a JSON number representing the number of nanoseconds in contrast to the v2 default of reporting an error.
This affects either marshaling or unmarshaling. The v1 default is true.
func MatchCaseSensitiveDelimiter 1.27
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 1.27
func MergeWithLegacySemantics(v bool) Options
MergeWithLegacySemantics specifies that unmarshaling into a non-zero Go value follows legacy semantics:
When unmarshaling a JSON null, this preserves the original Go value if the kind is a bool, int, uint, float, string, array, or struct. Otherwise, it zeros the Go value. In contrast, the default v2 behavior is to consistently and always zero the Go value when unmarshaling a JSON null into it.
When unmarshaling a JSON value other than null, this merges into the original Go value for array elements, slice elements, struct fields (but not map values), pointer values, and interface values (only if a non-nil pointer). For slices, it will merge into the pre-existing value of slice elements even for those past the slice length. If the original slice length was longer than the JSON array, then it is truncated to match. In contrast, the default v2 behavior is to merge into the Go value for struct fields, map values, pointer values, and interface values. In general, the v2 semantic merges when unmarshaling a JSON object, otherwise it replaces the original value.
This only affects unmarshaling and is ignored when marshaling. The v1 default is true.
func OmitEmptyWithLegacySemantics 1.27
func OmitEmptyWithLegacySemantics(v bool) Options
OmitEmptyWithLegacySemantics 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 ParseBytesWithLooseRFC4648 1.27
func ParseBytesWithLooseRFC4648(v bool) Options
ParseBytesWithLooseRFC4648 specifies that when parsing binary data encoded as "base32" or "base64", to ignore the presence of '\r' and '\n' characters. In contrast, the v2 default is to report an error in order to be strictly compliant with RFC 4648, section 3.3, which specifies that non-alphabet characters must be rejected.
This only affects unmarshaling and is ignored when marshaling. The v1 default is true.
func ParseTimeWithLooseRFC3339 1.27
func ParseTimeWithLooseRFC3339(v bool) Options
ParseTimeWithLooseRFC3339 specifies that a time.Time parses according to loose adherence to RFC 3339. In particular, it permits historically incorrect representations, allowing for deviations in hour format, sub-second separator, and timezone representation. In contrast, the default v2 behavior is to strictly comply with the grammar specified in RFC 3339.
This only affects unmarshaling and is ignored when marshaling. The v1 default is true.
func ReportErrorsWithLegacySemantics 1.27
func ReportErrorsWithLegacySemantics(v bool) Options
ReportErrorsWithLegacySemantics specifies that Marshal and Unmarshal should report errors with legacy semantics:
When marshaling or unmarshaling, the returned error values are usually of types such as SyntaxError, MarshalerError, UnsupportedTypeError, UnsupportedValueError, InvalidUnmarshalError, or UnmarshalTypeError. In contrast, the v2 semantic is to always return errors as either jsonv2.SemanticError or jsontext.SyntacticError.
When marshaling, if a user-defined marshal method reports an error, it is always wrapped in a MarshalerError, even if the error itself is already a MarshalerError, which may lead to multiple redundant layers of wrapping. In contrast, the v2 semantic is to always wrap an error within jsonv2.SemanticError unless it is already a semantic error.
When unmarshaling, if a user-defined unmarshal method reports an error, it is never wrapped and reported verbatim. In contrast, the v2 semantic is to always wrap an error within jsonv2.SemanticError unless it is already a semantic error.
When marshaling or unmarshaling, if a Go struct contains type errors (e.g., conflicting names or malformed field tags), then such errors are ignored and the Go struct uses a best-effort representation. In contrast, the v2 semantic is to report a runtime error.
When unmarshaling with jsonv2.MatchCaseInsensitiveNames, if a JSON object name has a non-exact match with multiple Go struct fields, then an error is not reported and instead the first declared field is used. In contrast, the v2 semantic is to report a runtime error.
When unmarshaling, the syntactic structure of the JSON input is fully validated before performing the semantic unmarshaling of the JSON data into the Go value. Practically speaking, this means that JSON input with syntactic errors do not result in any mutations of the target Go value. In contrast, the v2 semantic is to perform a streaming decode and gradually unmarshal the JSON input into the target Go value, which means that the Go value may be partially mutated when a syntactic error is encountered.
When unmarshaling, a semantic error does not immediately terminate the unmarshal procedure, but rather evaluation continues. When unmarshal returns, only the first semantic error is reported. In contrast, the v2 semantic is to terminate unmarshal the moment an error is encountered.
This affects either marshaling or unmarshaling. The v1 default is true.
func StringifyWithLegacySemantics 1.27
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. In contrast, the v2 default only allows the `string` tag option on Go types that would have otherwise serialized as a JSON number, and stringifies the JSON number within a JSON string. In particular, the v2 default does not stringify Go bools and strings. If ReportErrorsWithLegacySemantics is false, then incorrect usages of `string` result in a runtime error.
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 or Go number representation for that numeric kind. Note that the Go number grammar is a superset of the JSON number grammar. 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. In contrast, the v2 default rejects stringified numbers outside of the grammar for a JSON number and also rejects a JSON null quoted in a JSON string.
This affects either marshaling or unmarshaling. The v1 default is true.
func UnmarshalArrayFromAnyLength 1.27
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. In contrast, the v2 default expects that Go arrays be unmarshaled from input JSON arrays of the exact same length.
This only affects unmarshaling and is ignored when marshaling. The v1 default is true.
type RawMessage
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.
type RawMessage = jsontext.Value
▸ Example (Marshal)
▸ Example (Unmarshal)
type SyntaxError
A SyntaxError is a description of a JSON syntax error. Unmarshal will return a SyntaxError if the JSON can't be parsed.
type SyntaxError struct {
Offset int64 // error occurred after reading Offset bytes
// contains filtered or unexported fields
}
func (*SyntaxError) Error
func (e *SyntaxError) Error() string
type Token 1.5
A Token holds a value of one of these types:
- Delim, for the four JSON delimiters [ ] { }
- bool, for JSON booleans
- float64, for JSON numbers
- Number, for JSON numbers
- string, for JSON string literals
- nil, for JSON null
type Token any
type UnmarshalFieldError
An UnmarshalFieldError describes a JSON object key that led to an unexported (and therefore unwritable) struct field.
Deprecated: No longer used; kept for compatibility.
type UnmarshalFieldError struct {
Key string
Type reflect.Type
Field reflect.StructField
}
func (*UnmarshalFieldError) Error
func (e *UnmarshalFieldError) Error() string
type UnmarshalTypeError
An UnmarshalTypeError describes a JSON value that was not appropriate for a value of a specific Go type.
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; added in Go 1.5
Struct string // name of the root type containing the field; added in Go 1.8
Field string // the full path from root node to the value; added in Go 1.8
Err error // may be nil; added in Go 1.27
}
func (*UnmarshalTypeError) Error
func (e *UnmarshalTypeError) Error() string
func (*UnmarshalTypeError) Unwrap 1.27
func (e *UnmarshalTypeError) Unwrap() error
type 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 Unmarshaler = jsonv2.Unmarshaler
type UnsupportedTypeError
An UnsupportedTypeError is returned by Marshal when attempting to encode an unsupported value type.
type UnsupportedTypeError struct {
Type reflect.Type
}
func (*UnsupportedTypeError) Error
func (e *UnsupportedTypeError) Error() string
type UnsupportedValueError
An UnsupportedValueError is returned by Marshal when attempting to encode an unsupported value.
type UnsupportedValueError struct {
Value reflect.Value
Str string
}
func (*UnsupportedValueError) Error
func (e *UnsupportedValueError) Error() string