[BUG]: Missing additionalProperties mapping

[dmipeck]

Quicktype does not generate a field for additionalProperties in the output Go struct

Issue Type

Quicktype output

Context (Environment, Version, Language)

Input Format: JSON Schema
Output Language: Go

CLI, npm, or app.quicktype.io: CLI
Version: 23.0.171

Description

The devcontainer base schema uses additionalProperties for defining a set of devcontainer features. Without a field to read the map of additional properties it's not possible to implement the features spec without modifying the generated Go code or the original schema JSON.

Input Data

test.schema.json:

{
    "$schema": "https://json-schema.org/draft/2019-09/schema",
    "type": "object",
    "properties": {
        "deprecatedField": {
            "deprecated": true
        }
    },
    "additionalProperties": true
}

Expected Behaviour / Output

The generated struct contains fields for the deprecated field, plus some field for accessing additionalProperties, e.g:

type TestSchema struct {
        DeprecatedField interface{} `json:"deprecatedField"`
        AdditionalProperties map[string]interface{}
}

Current Behaviour / Output

Only the deprecated field is generated:

type TestSchema struct {
        DeprecatedField interface{} `json:"deprecatedField"`
}

Steps to Reproduce

run with the schema input above:

quicktype --lang go --src-lang schema --src ./test.schema.json

[Dogacel]

I have also faced this issue while trying to generate models for MCP (https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json#L1657)

I had to modify the generated classes manually. I think this is a huge blocker and it makes the tool much less useful, as if you need to modify the generated code, you don't really get the benefit of auto-generation. I bet AI can generate better code at this point 🙂

Let me know if you have any suggestions and workarounds. I am looking for answers that would enable me to use auto-generated stubs directly. I also accept other library recommendations?