goType errorMedium

JSON Unmarshal fails to populate struct fields silently

Time: 0:00

BugFind the bug and fix the code

What it should do

Parse JSON data into a Go struct. Example: parseJSON(jsonData) -> myStruct

What happens instead

No compiler or runtime errors, but struct fields are not populated

package main

import (
	"encoding/json"
	"fmt"
)

type MyStruct struct {
	name string
	age  int
}

func parseJSON(data []byte) MyStruct {
	var s MyStruct
	json.Unmarshal(data, &s)
	return s
}

func main() {
	jsonData := []byte(`{"name":"Alice","age":30}`)
	s := parseJSON(jsonData)
	fmt.Println(s)
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

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This bug belongs to the type errors pattern

Totals that concatenate, sorts that put 10 before 9, comparisons that refuse to run.

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package main import ( "encoding/json" "fmt" ) type MyStruct struct { name string age int } func parseJSON(data []byte) MyStruct { var s MyStruct json.Unmarshal(data, &s) return s } func main() { jsonData := []byte(`{"name":"Alice","age":30}`) s := parseJSON(jsonData) fmt.Println(s) }

JSON Unmarshal fails to populate struct fields silently

What it should do

What happens instead

More type errors to practise

JSON Unmarshal fails to populate struct fields silently

What it should do

What happens instead

More type errors to practise