A preliminary JsonSchema -> Avro conversion chart

json_to_avro.md

A guardrail means that it must be checked against.

JsonSchema Property	AvroSchema Support	IsConvertable	Description	Guardrail?
AnyOf	Union (Somewhat fit)	✅
AllOf	Not supported	⛔	This cannot be expressed in Avro	Yes
OneOf	Union (Best fit)	✅
Nullable	Union (null + another Type)	✅
Title	Schema.Name	✅	Must be guardrail as avro requires "Name" for its types.	Yes
Type	AvroRecord, AvroArray, AvroMap, AvroEnum (with Symbols) or primitive (see picture)	✅	Must be guardrailed as avro needs a type to convert into.	Yes
Description	Schema.Doc	✅
Default	Field:Default	✅
Properties	Record.Fields	✅
PatternProperties		⛔	This cannot be expressed in Avro
ExternalDocs		⛔	There is only "Doc" which is better suited as a description.
Items	If Array, AvroArray.Items	✅
AdditionalItems		⛔	This cannot be expressed in Avro
Deprecated		⛔	This cannot be expressed in Avro
Enum	Enum - only if string though.	✅		Maybe?

Example Conversion

JsonSchema

{
  "title": "Example Schema",
  "description": "An example schema representing a person",
  "type": "object",
  "properties": {
    "name": {"type": "string"},
    "age": {"type": "integer", "minimum": 18, "maximum": 120, "default": 50},
    "address": {
      "type": "object",
      "properties": {
        "street": {"type": "string"},
        "zip": {"type": "integer"}
      },
      "required": ["street", "zip"]
    },
    "Wishes": {
      "type": "array",
      "items": {
        "oneOf": [
          {"properties": {"name": {"type": "string"}, "description": {"type": "string"}}},
          {"properties": {"url": {"type": "string"}}},
          {"type": "null"}
        ]
      }
    },
    "Animals": {
	    "items": { "title": "animal", "properties": {"name": {"type": "string"}, "characteristic": {"type": "string"}}},
    },
    "Hobbies": {
      "type": "array",
      "items": {"type": "string", "default": "baseball"}
    },
    "grade": {"type": "enum", "enum": ["A", "B", "C", "D"]}
  }
}

Avro

{
  "type": "record", // Inferred from 'Properties' being present
  "name": "Example Schema", // 'Title'
  "doc": "An example schema representing a person", // 'Description'
  "fields": [ // 'Properties'
    {"name": "name", "type": "string"},
    {"name": "age", "type": "int", "default": 50},
    {
      "type": "record",
      "name": "Address",
      "fields": [
        {"name": "street", "type": "string"},
        {"name": "zip", "type": "int"}
      ]
    },
    {
      "name": "Wishes",
      "type": "array", // inferred from 'Items' being present.
      "items": [ // if type has 'oneOf'/'anyOf' map to Union
        {
          "type": "record", // Inferred from 'Properties' being present
          "name": "Wish1", // Infer from name add count?
          "fields": [ // 'Properties'
            {"name": "name", "type": "string"},
            {"name": "description", "type": "string"}
          ]
        },
        {
          "type": "record", // Inferred from 'Properties' being present
          "name": "Wish2", // Infer from name add count?
          "fields": [ // 'Properties'
            {"name": "url", "type": "string"}
          ]
        },
        { "type": "null" } // primitive null.
      ]
    },
    {
			"name": "Animals",
			"type": "array", // inferred from 'Items' being present.
			"items": { 
			  "type": "record", // inferred from 'Properties' being present.
			  "name":"animal", // 'Title'
			  "fields": [ // 'Properties'
          {"name": "name", "type": "string"},
          {"name": "characteristic", "type": "string"}
        ]
      }
    },
    {
      "name": "Hobbies",
      "type": "array", // inferred from 'Items' being present.
      "items": "string" // No default, 'Type' was a primitive
    },
    { 
    
    
      "name": "grade",
      "type": "enum", // Inferred from 'Enum' being present
      "symbols": ["A", "B", "C", "D"]
    }
  ]
}