Support for Union of Complex Types

[sj-freitas]

Hello, first of all, thanks for the library!

Currently we found that in the avro-schema reference there is support for multiple complex union types, however using avsc we found that schemas such as this:

const employeeSchema = avro.Type.forSchema({
  name: 'Employee',
  type: 'record',
  fields: [
    { name: 'name', type: 'string' },
    {
      name: 'role',
      type: [
        {
          name: 'Manager',
          type: 'record',
          fields: [
            {
              name: 'managees',
              type: { type: 'array', items: 'string' },
            },
          ],
        },
        {
          name: 'Developer',
          type: 'record',
          fields: [{ name: 'programmingLanguage', type: 'string' }],
        },
      ],
    },
  ],
});

When we do the following:

const employee = {
  name: 'Alice',
  role: {
    programmingLanguage: 'Typescript',
  },
};

// Throws an exception!
const buffered = employeeSchema.toBuffer(dummyValue);

We get this error message:
invalid [{"name":"Manager","type":"record","fields":[{"name":"managees","type":{"type":"array","items":"string"}}]},{"name":"Developer","type":"record","fields":[{"name":"programmingLanguage","type":"string"}]}]: {"programmingLanguage":"Typescript"}

We'd like to know if this is a problem with our interpretation of the documentation of the avro-schema or if there's any workaround that we can do to support union complex types.

[mtth]

Hi @sj-freitas. The issue you're bumping into is that unions with multiple records need to be wrapped to ensure that they don't lose branch information. For your example, you'll need to tweak the data as follows:

const employee = {
  name: 'Alice',
  role: {
    Developer: { // Note this extra key, matching the branch's record's name.
      programmingLanguage: 'TypeScript',
    },
  },
};

Take a look at this comment for more context as well as a couple examples.

[sj-freitas]

Thank you very much! I looked into the logicalTypes and I managed to find a solution!