jsonfields

Documentation

Overview

Package jsonfields finds the fields encoding/json reads from a JSON object into a Go struct. The schema package describes them and the strict decoder checks arguments against them, so a schema and its decoder agree on every name and on which fields are required.

Index

• type Field
  • func Of(t reflect.Type) ([]Field, error)
  • func (f Field) Required() bool
• type TagNameError
  • func (e *TagNameError) Error() string

Types

type Field

type Field struct {
	Name     string
	Tagged   bool  // the name came from a json tag
	Index    []int // the field's index path from the outer struct
	Field    reflect.StructField
	Type     reflect.Type // the field's type, with an unnamed pointer followed
	Optional bool         // ",omitempty" or ",omitzero"
	Quoted   bool         // ",string" on a string, number, or boolean field
	// ViaUnexportedPtr names the unexported struct type of an embedded pointer on the field's
	// path, if any: encoding/json cannot allocate it, so decoding the field fails.
	ViaUnexportedPtr string
}

Field is one field encoding/json reads from a JSON object into a struct.

func Of

func Of(t reflect.Type) ([]Field, error)

Of returns the fields encoding/json reads for struct type t, in index order. It is a port of encoding/json's typeFields: a breadth-first walk over embedded structs, then Go's dominance rules (the shallowest name wins, a json tag breaks a tie at one depth, and any other tie removes the name). A json tag name encoding/json does not accept is a *TagNameError.

func (Field) Required

func (f Field) Required() bool

Required reports whether the field is required: it is not a pointer, and its json tag has neither ",omitempty" nor ",omitzero". This is the one definition the schema's "required" list and the strict decoder's missing-field check share.

type TagNameError

type TagNameError struct {
	Struct reflect.Type
	Field  string // the Go field name
	Name   string // the tag name
}

TagNameError reports a json tag name encoding/json does not accept (one with a quote, a backslash, or another reserved character). encoding/json v1 falls back to the Go name there and its v2 implementation reads the name differently, so the field has no one JSON name.

func (*TagNameError) Error

func (e *TagNameError) Error() string

Error names the struct, the field and the rejected tag name.