Foxglove Studio does not appear to understand json-schema $ref in schemas

[kenaniah]

Description

• Version: 1.86.1 (darwin)
• Platform: MacOS
• Data source (e.g. bag file, mcap file, rosbridge, ROS 1/2 native): MCAP file

It appears as though Foxglove Studio does not properly parse json-schema schemas. The following reproduction steps suggest that $ref is not handled, and the Foxglove Studio documentation does not make it clear which features of json-schema are supported or not supported.

Steps To Reproduce

1. Add a channel with a json-schema that uses references, for example:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "TracksMessage",
  "type": "object",
  "required": [
    "objects",
    "total"
  ],
  "properties": {
    "objects": {
      "type": "array",
      "items": {
        "$ref": "#/definitions/TrackObject"
      }
    },
    "total": {
      "type": "integer",
      "format": "uint",
      "minimum": 0.0
    }
  },
  "definitions": {
    "TrackObject": {
      "type": "object",
      "required": [
        "altitude",
        "first_seen",
        "heading",
        "id",
        "last_seen",
        "latitude",
        "longitude",
        "source_type"
      ],
      "properties": {
        "altitude": {
          "type": "number",
          "format": "double"
        },
        "first_seen": {
          "type": "string",
          "format": "date-time"
        },
        "heading": {
          "type": "number",
          "format": "double"
        },
        "id": {
          "type": "string"
        },
        "last_seen": {
          "type": "string",
          "format": "date-time"
        },
        "latitude": {
          "type": "number",
          "format": "double"
        },
        "longitude": {
          "type": "number",
          "format": "double"
        },
        "on_ground": {
          "type": [
            "boolean",
            "null"
          ]
        },
        "source_type": {
          "$ref": "#/definitions/SourceType"
        },
        "tail_number": {
          "type": [
            "string",
            "null"
          ]
        }
      }
    },
    "SourceType": {
      "description": "Source type",
      "oneOf": [
        {
          "description": "ADS-B",
          "type": "string",
          "enum": [
            "ADSB"
          ]
        },
        {
          "description": "FAA Terrestrial",
          "type": "string",
          "enum": [
            "ASDI"
          ]
        }
      ]
    }
  }
}

2. Record some data to that topic in an MCAP file.

3. Attempt to open the MCAP file in Foxglove Studio

Expected Behavior

File should open without issues and the topic's schema should be parsed correctly.

Actual Behavior

Error in topic ... (channel 1): Unsupported type undefined for array item objects

[foxhubber[bot]]

Internal tracking ticket: FG-6486

[defunctzombie]

Thanks for reporting. This is a known limitation and we have a better error message now.