75 lines
1.9 KiB
Go
75 lines
1.9 KiB
Go
// Package jsonvalue holds a decoded JSON value whose numbers keep the text they are written in.
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package jsonvalue
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import (
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"bytes"
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"encoding/json"
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"errors"
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"fmt"
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"unicode/utf8"
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)
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// Value is a JSON value that only Decode, String and Object make, so a template never compiles
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// from a value encoding/json decoded with its numbers as float64. The zero Value is JSON null.
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type Value struct{ v any }
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// Decode decodes one JSON value, keeping each number as the json.Number it is written as.
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func Decode(b []byte) (Value, error) {
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var v any
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if !json.Valid(b) {
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return Value{}, located(b, json.Unmarshal(b, &v))
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}
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dec := json.NewDecoder(bytes.NewReader(b))
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dec.UseNumber()
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err := dec.Decode(&v)
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return Value{v}, err
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}
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// located prefixes a syntax error with the line and column where decoding stopped.
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func located(b []byte, err error) error {
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var syntax *json.SyntaxError
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if !errors.As(err, &syntax) {
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return err
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}
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before := b[:max(syntax.Offset-1, 0)]
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line := bytes.Count(before, []byte("\n")) + 1
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column := utf8.RuneCount(before[bytes.LastIndexByte(before, '\n')+1:]) + 1
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return fmt.Errorf("line %d, column %d: %w", line, column, err)
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}
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// String is the JSON string s.
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func String(s string) Value { return Value{s} }
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// Object is the JSON object holding fields.
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func Object(fields map[string]Value) Value {
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m := make(map[string]any, len(fields))
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for k, f := range fields {
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m[k] = f.v
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}
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return Value{m}
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}
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// Any is the value as encoding/json decodes it: a map[string]any, []any, string, json.Number,
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// bool or nil.
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func (v Value) Any() any { return v.v }
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// Kind names the kind of a value as Any gives it, in the data format's own terms, such as
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// "a number" or "a list".
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func Kind(v any) string {
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switch v.(type) {
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case json.Number:
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return "a number"
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case bool:
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return "a boolean"
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case string:
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return "a string"
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case []any:
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return "a list"
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case map[string]any:
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return "an object"
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case nil:
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return "null"
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}
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return fmt.Sprintf("%T", v)
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}
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