Add uniqueItems to set and frozenset json schema

src/msgspec/_json_schema.py

@@ -284,6 +284,8 @@ def to_schema(self, t: mi.Type, check_ref: bool = True) -> dict[str, Any]:
                 schema["maxItems"] = t.max_length
             if t.min_length is not None:
                 schema["minItems"] = t.min_length
+            if isinstance(t, (mi.SetType, mi.FrozenSetType)):
+                schema["uniqueItems"] = True
         elif isinstance(t, mi.TupleType):
             schema["type"] = "array"
             schema["minItems"] = schema["maxItems"] = len(t.item_types)

tests/unit/test_schema.py

@@ -173,22 +173,33 @@ def test_newtype():
     }
 
 
-@pytest.mark.parametrize(
-    "typ", [list, tuple, set, frozenset, List, Tuple, Set, FrozenSet]
-)
+@pytest.mark.parametrize("typ", [list, tuple, List, Tuple])
 def test_sequence_any(typ):
     assert msgspec.json.schema(typ) == {"type": "array"}
 
 
-@pytest.mark.parametrize(
-    "cls", [list, tuple, set, frozenset, List, Tuple, Set, FrozenSet]
-)
+@pytest.mark.parametrize("cls", [list, tuple, List, Tuple])
 def test_sequence_typed(cls):
     args = (int, ...) if cls in (tuple, Tuple) else int
     typ = cls[args]
     assert msgspec.json.schema(typ) == {"type": "array", "items": {"type": "integer"}}
 
 
+@pytest.mark.parametrize("typ", [set, frozenset, Set, FrozenSet])
+def test_set_any(typ):
+    assert msgspec.json.schema(typ) == {"type": "array", "uniqueItems": True}
+
+
+@pytest.mark.parametrize("cls", [set, frozenset, Set, FrozenSet])
+def test_set_typed(cls):
+    typ = cls[int]
+    assert msgspec.json.schema(typ) == {
+        "type": "array",
+        "uniqueItems": True,
+        "items": {"type": "integer"},
+    }
+
+
 @pytest.mark.parametrize("cls", [tuple, Tuple])
 def test_tuple(cls):
     typ = cls[int, float, str]
@@ -1105,7 +1116,7 @@ def test_binary_metadata(typ, field, n, constraint):
     }
 
 
-@pytest.mark.parametrize("typ", [list, tuple, set, frozenset])
+@pytest.mark.parametrize("typ", [list, tuple])
 @pytest.mark.parametrize(
     "field, constraint",
     [("min_length", "minItems"), ("max_length", "maxItems")],
@@ -1115,6 +1126,21 @@ def test_array_metadata(typ, field, constraint):
     assert msgspec.json.schema(typ) == {"type": "array", constraint: 2}
 
 
+@pytest.mark.parametrize("typ", [set, frozenset])
+@pytest.mark.parametrize(
+    "field, constraint",
+    [("min_length", "minItems"), ("max_length", "maxItems")],
+)
+def test_set_metadata(typ, field, constraint):
+    typ = Annotated[typ[int], Meta(**{field: 2})]
+    assert msgspec.json.schema(typ) == {
+        "type": "array",
+        "uniqueItems": True,
+        "items": {"type": "integer"},
+        constraint: 2,
+    }
+
+
 @pytest.mark.parametrize(
     "field, constraint",
     [("min_length", "minProperties"), ("max_length", "maxProperties")],
@@ -1209,7 +1235,15 @@ class ExDataclass:
             "properties": {
                 "b": {
                     "anyOf": [
-                        {"items": {"items": r1, "type": "array"}, "type": "array"},
+                        {
+                            "items": {
+                                "items": r1,
+                                "type": "array",
+                                "uniqueItems": True,
+                            },
+                            "type": "array",
+                            "uniqueItems": True,
+                        },
                         {"type": "integer"},
                     ]
                 }