Fix invalid regex in unconstrained arrays for json_schema.py

outlines/fsm/json_schema.py

@@ -297,15 +297,22 @@ def to_regex(
                 # Here we need to make the choice to exclude generating list of objects
                 # if the specification of the object is not given, even though a JSON
                 # object that contains an object here would be valid under the specification.
-                types = [
+                legal_types = [
                     {"type": "boolean"},
                     {"type": "null"},
                     {"type": "number"},
                     {"type": "integer"},
                     {"type": "string"},
                 ]
-                regexes = [to_regex(resolver, t, whitespace_pattern) for t in types]
-                return rf"\[{whitespace_pattern}({'|'.join(regexes)})(,{whitespace_pattern}({'|'.join(regexes)})){num_repeats}){allow_empty}{whitespace_pattern}\]"
+                depth = instance.get("depth", 2)
+                if depth > 0:
+                    legal_types.append({"type": "object", "depth": depth - 1})
+                    legal_types.append({"type": "array", "depth": depth - 1})
+
+                regexes = [
+                    to_regex(resolver, t, whitespace_pattern) for t in legal_types
+                ]
+                return rf"\[{whitespace_pattern}({'|'.join(regexes)})(,{whitespace_pattern}({'|'.join(regexes)})){num_repeats}{allow_empty}{whitespace_pattern}\]"
 
         elif instance_type == "object":
             # pattern for json object with values defined by instance["additionalProperties"]
@@ -328,20 +335,20 @@ def to_regex(
                 # unset or True, it is unconstrained object.
                 # We handle this by setting additionalProperties to anyOf: {all types}
 
-                legal_values = [
+                legal_types = [
                     {"type": "string"},
                     {"type": "number"},
                     {"type": "boolean"},
-                    {"type": "null"}
-                    # { "type": "array" },  # TODO: enable arrays within object-types
+                    {"type": "null"},
                 ]
 
                 # We set the object depth to 2 to keep the expression finite, but the "depth"
                 # key is not a true component of the JSON Schema specification.
                 depth = instance.get("depth", 2)
                 if depth > 0:
-                    legal_values.append({"type": "object", "depth": depth - 1})
-                additional_properties = {"anyOf": legal_values}
+                    legal_types.append({"type": "object", "depth": depth - 1})
+                    legal_types.append({"type": "array", "depth": depth - 1})
+                additional_properties = {"anyOf": legal_types}
 
             value_pattern = to_regex(
                 resolver, additional_properties, whitespace_pattern

tests/fsm/test_json_schema.py

@@ -719,6 +719,46 @@ def test_format(schema, regex, examples):
                 ('{"time":20:20:39Z}', False),  # missing quotes for value
             ],
         ),
+        # Unconstrained Object
+        (
+            {
+                "title": "Foo",
+                "type": "object",
+            },
+            [
+                ("{}", True),
+                ('{"a": 1, "b": null}', True),
+                ('{"a": {"z": {"g": 4}}, "b": null}', True),
+                ("1234", False),  # not an object
+                ('["a", "a"]', False),  # not an array
+            ],
+        ),
+        # Unconstrained Array
+        (
+            {
+                "type": "array",
+            },
+            [
+                ("[1, {}, false]", True),
+                ("[{}]", True),
+                ('[{"a": {"z": "q"}, "b": null}]', True),
+                ('[{"a": [1, 2, true], "b": null}]', True),
+                ('[{"a": [1, 2, true], "b": {"a": "b"}}, 1, true, [1, [2]]]', True),
+                # too deep, default unconstrained depth limit = 2
+                (
+                    '[{"a": [1, 2, true], "b": {"a": "b"}}, 1, true, [1, [2, [3]]]]',
+                    False,
+                ),
+                ('[{"a": {"z": {"g": 4}}, "b": null}]', False),
+                ("[[[[1]]]]", False),
+                # not an array
+                ("{}", False),
+                ('{"a": 1, "b": null}', False),
+                ('{"a": {"z": {"g": 4}}, "b": null}', False),
+                ("1234", False),  # not an array
+                ('{"a": "a"}', False),  # not an array
+            ],
+        ),
     ],
 )
 def test_format_without_regex(schema, examples):