JSON Schema validation for a complex comination of AND/OR - json

Question

Similar to this question. But it's a little more complicated because I need to validate fields in a list of objects.
{
"$schema": "http://json-schema.org/draft-07/schema#",
"title": "All the Fruits",
"type": "object",
"properties":
{
"fruit":
{
"enum":
[
"apple",
"orange",
"banana",
"watermelon",
"all_fruit"
]
}
},
"required":
[
"fruit"
],
"additionalProperties": false
}
And it's used here in a different file:
{
"$schema": "http://json-schema.org/draft-07/schema#",
"title": "Fruit basket",
"type": "object",
"properties":
{
"type":
{
"enum":
[
"fruit_basket"
]
},
"fruits":
{
"description": "List of fruits",
"type": "array",
"items":
{
"$ref": "fruit/fruits.schema.json#"
},
"uniqueItems": true,
{
// What do I add here?
}
}
"required":
[
"fruits"
]
"additionalProperties": false
}
Is there a way to validate JSON such that I can pick any subset of fruits or "all_fruit" not both.
Valid cases:
["apple","orange"]
["apple","banana"]
["all_fruit"]
Invalid:
["all_fruit", "apple"]
all_fruit cannot exist with anything else.
Edit:
I tried this:
...
...
"uniqueItems": true,
"if" : {
"properties": {
"fruits": {
"const": "all_fruit"
}
}
},
"then": {
"maxItems": 1,
"minItems": 1
}
...
...
But the condition seems to be satisfied always. Even when I don't use all_fruit and the validation errors out saying maxItems expected is 1.

Answer 1

See https://json-schema.org/understanding-json-schema/reference/conditionals.html and https://json-schema.org/understanding-json-schema/reference/array.html
-- in pseudocode, you'd want:
if the list is exactly the value of ["all_fruit"],
then maximum items is 1.
If "all_fruit" could coexist with some values but not all, you could instead use contains instead of const for the conditional.