How to Dynamically Convert YAML to JSON in Go without Predefined Structs?

Convert YAML to JSON Dynamically without a Defined Struct

You have a dynamic YAML configuration string that you want to convert to JSON. However, you cannot define a struct for the JSON because the data structure is unknown.

To overcome this challenge, you can use the yaml.Unmarshal() function to parse the YAML into an interface{} value. This will produce a nested data structure of maps and slices with the default interface{} type.

The problem arises when you try to convert this interface{} value back to JSON using json.Marshal(). It will fail because json.Marshal() does not support the map[interface{}]interface{} type.

To handle this dynamic data structure, you need to recursively convert the map[interface{}]interface{} values to map[string]interface{} values. This ensures that all maps have string keys, which are supported by JSON.

Here's an example converter function:

func convert(i interface{}) interface{} {
    switch x := i.(type) {
    case map[interface{}]interface{}:
        m2 := map[string]interface{}{}
        for k, v := range x {
            m2[k.(string)] = convert(v)
        }
        return m2
    case []interface{}:
        for i, v := range x {
            x[i] = convert(v)
        }
    }
    return i
}

Using this function, you can convert the interface{} value to a JSON-compatible data structure:

body = convert(body)

Now, you can use json.Marshal() to convert the converted body to a JSON string.

Here's a complete example:

func main() {
    const s = `Services:
-   Orders:
    -   ID: $save ID1
        SupplierOrderCode: $SupplierOrderCode
    -   ID: $save ID2
        SupplierOrderCode: 111111
`
    var body interface{}
    if err := yaml.Unmarshal([]byte(s), &body); err != nil {
        panic(err)
    }

    body = convert(body)

    if b, err := json.Marshal(body); err != nil {
        panic(err)
    } else {
        fmt.Printf("Output: %s\n", b)
    }
}

Output:

Output: {"Services":[{"Orders":[{"ID":"$save ID1","SupplierOrderCode":"$SupplierOrderCode"},{"ID":"$save ID2","SupplierOrderCode":111111}]}]}

Note that the order of elements in the JSON output may differ from the original YAML due to the unordered nature of Go maps.

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