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https://github.com/liamg/jfather

JSON parsing with extra metadata
https://github.com/liamg/jfather

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JSON parsing with extra metadata

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# jfather

[![build](https://github.com/liamg/jfather/actions/workflows/test.yml/badge.svg)](https://github.com/liamg/jfather/actions/workflows/test.yml)

Parse JSON with line numbers and more!

This is a JSON parsing module that provides additional information during the unmarshalling process, such as line numbers, columns etc.

You can use jfather to unmarshal JSON just like the `encoding/json` package, and add your own unmarshalling functionality to gather metadata by implementing the `jfather.Umarshaller` interface. This requires a single method with the signature `UnmarshalJSONWithMetadata(node jfather.Node) error`. A full example is below.

You should not use this package unless you need the line/column metadata, as unmarshalling is typically much slower than the `encoding/json` package:

```
BenchmarkUnmarshal_JFather-8 39483 34222 ns/op
BenchmarkUnmarshal_Traditional-8 176756 7244 ns/op
```

## Full Example

```golang
package main

import (
"fmt"

"github.com/liamg/jfather"
)

type ExampleParent struct {
Child ExampleChild `json:"child"`
}

type ExampleChild struct {
Name string
Line int
Column int
}

func (t *ExampleChild) UnmarshalJSONWithMetadata(node jfather.Node) error {
t.Line = node.Range().Start.Line
t.Column = node.Range().Start.Column
return node.Decode(&t.Name)
}

func main() {
input := []byte(`{
"child": "secret"
}`)
var parent ExampleParent
if err := jfather.Unmarshal(input, &parent); err != nil {
panic(err)
}

fmt.Printf("Child value is at line %d, column %d, and is set to '%s'\n",
parent.Child.Line, parent.Child.Column, parent.Child.Name)

// outputs:
// Child value is at line 2, column 12, and is set to 'secret'
}
```