JDT Serialization with Only Additional Properties fails

[fabianeichinger]

My JTD schemas contain records that have either only additionalAttributes: true (i.e. no fixed internal structure) or optionalAttributes with additionalAttributes: true (where we want type safety for some attributes and pass others through). Serialization always fails in the first case and also in the second if no optionalAttributes are set in the data. This issue is very likely related to #2001 but that one only mentions optionalProperties.

What version of Ajv are you using? Does the issue happen if you use the latest version?
8.11.2

Ajv options object

not dependent on options

JSON Schema

schema1

{ 
  "properties": {},
  "additionalProperties": true
}

Same result with optionalProperties instead of properties (schema2)

schema3

{
  "optionalProperties": {
    "prop_not_in_data": { "type": "string" }
  },
  "additionalProperties": true
}

Sample data

{
  "a":1,
  "b":2
}

Your code

var serialize1 = ajv.compileSerializer(schema1)
var serialize2 = ajv.compileSerializer(schema2)
var serialize3 = ajv.compileSerializer(schema3)

console.log("serialize1", serialize1(data))
console.log("serialize2", serialize2(data))
console.log("serialize3", serialize3(data))

https://runkit.com/fabianeichinger/637bc56844c590000adfb57d

Serialization output

serialize1: {"a":1"b":2}
serialize2: {"a":1"b":2}
serialize3: {,"a":1,"b":2}

What results did you expect?
Valid JSON

Are you going to resolve the issue?
Would love to test if this is resolved by #2028. Can't get the build to work on my machine, getting some TS errors on npm install.

[epoberezkin]

duplicate of #2001