`z.intersection()` compiles to unsatisfiable schema

[za-creature]

The intersection of two objects

z.toJSONSchema(z.intersection(
    z.object({foo: z.boolean()}),
    z.object({bar: z.boolean()}),
))

compiles to:

{ "allOf": [{
    "type": "object",
    "properties": { "foo": { "type": "boolean" } },
    "required": ["foo"],
    "additionalProperties": false
}, {
    "type": "object",
    "properties": { "bar": { "type": "boolean" } },
    "required": [ "bar" ],
    "additionalProperties": false
}]}

where additionalProperties: false prevents { foo: true, bar: false } from matching at least one of the rules.

.looseObject works around this but isn't strict enough for my taste so for now I'm stuck with extending union cases

Maybe this helps?

[dosubot]

Hi @za-creature! I'm Dosu and I’m helping the zod team.

This is a known outcome of how Zod's strict objects are translated to JSON Schema: each object in the intersection gets additionalProperties: false, so the resulting allOf schema is unsatisfiable for objects containing properties from both branches. This matches Zod's output type behavior, but it doesn't play well with JSON Schema validators see discussion.

Zod does not currently emit the unevaluatedProperties keyword in its JSON Schema output, even though the default target is draft 2020-12 (which supports it). The exporter only sets additionalProperties and does not have built-in logic for unevaluatedProperties docs.

Workarounds:

• Use z.looseObject() instead of z.object() if you can accept extra properties (but this is less strict).
• Use the override option in z.toJSONSchema to remove additionalProperties from the generated schema. Example:

  z.toJSONSchema(schema, {
    override(ctx) {
      if (ctx.jsonSchema.additionalProperties !== undefined) {
        delete ctx.jsonSchema.additionalProperties;
      }
    }
  })

• If you want to experiment, you could use the override to inject unevaluatedProperties: false at the top level, but Zod doesn't do this automatically.

For more details and maintainer commentary, see this GitHub issue. If this answers your question, please close the issue!

To reply, just mention @dosu.

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[za-creature]

This matches Zod's output type behavior

let Intersection = z.intersection(
    z.object({foo: z.boolean()}),
    z.object({bar: z.boolean()}),
)
let obj : z.infer<typeof Intersection> = { foo: true, bar: false }

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