Clarum JSON

Library used by the clarum framework to do JSON validation.

Features

The Comparator validates if two JSON objects match and:

• returns detailed errors on where and how they do not match
• errors are accompanied by json paths (when one can be provided)
• allows ignoring values of fields

How to use

The recommended way is to create a Comparator using the builder and then use it to compare two JSON objects:

expectedValue := []byte("{" +
"\"active\": true," +
" \"name\": \"Bruce\"," +
" \"age\": 37," +
" \"height\": 1.879," +
"\"location\": {" +
"\"street\": \"Mountain Drive\"," +
"\"number\": 1007," +
"\"hidden\": false," +
"\"timestamp\": \"@ignore@\"" +
"}" +
"}")

actualValue := []byte("{" +
"\"active\": true," +
" \"name\": \"Bruce Wayne\"," +
" \"age\": 38," +
" \"height\": 1.879," +
"\"location\": {" +
"\"address\": \"Mountain Drive\"," +
"\"number\": 1008," +
"\"hidden\": true," +
"\"timestamp\": \"2024-01-03 23:42:00\"" +
"}" +
"}")

jc := comparator.NewComparator().Build()

_, err := jc.Compare(expectedValue, actualValue)

// err will contain the following validation errors:
//
// "[$.name] - value mismatch - expected [Bruce] but received [Bruce Wayne]"
// "[$.age] - value mismatch - expected [37] but received [38]"
// "[$.location.street] - field is missing"
// "[$.location.number] - value mismatch - expected [1007] but received [1008]"
// "[$.location.hidden] - value mismatch - expected [false] but received [true]"
// "[$.location.address] - unexpected field"

Recorder

The Recorder is an optional feature that returns a user-friendly output which makes it easier to see where the validation has failed. By default, a NoopRecorder is configured.

In the example above we can configure a different recorder like this:

jc := NewComparator().
Recorder(recorder.NewDefaultRecorder()).
Build()

recorderLog, err := jc.Compare(expectedValue, actualValue)

The recorderLog will be a string that will look like this:

{
  "location": {
    "timestamp":  <-- ignoring field
     X-- missing field [street]
    "number": 1008, <-- value mismatch - expected [1007]
    "hidden": true, <-- value mismatch - expected [false]
    "address":  <-- unexpected field
  },
  "active": true,
  "name": Bruce Wayne, <-- value mismatch - expected [Bruce]
  "age": 38, <-- value mismatch - expected [37]
  "height": 1.879,
}

Configuration

Key	Default	Description
StrictObjectCheck	true	Determines if the Comparator will do a strict check on object fields If set to true, the following checks will be done: - actual JSON has the same number of fields - actual JSON has extra unexpected fields
Logger	slog.Default()	Logger used internally by the Comparator
Recorder	NoopRecorder	Recorder implementation to be used

Ignoring field values

The comparator allows you to validate if a field is present but ignore its value.

For example some entities may have a modifiedAt field which is a timestamp. We want to validate that the field exists but cannot really predict its value. In such a case we can use the special @ignore@ marker as the value of the field in our expected JSON object. For an example check the code from How to use.