Better {not: {anyOf: ...}} handling

We now flatten nexted anyOf chains, and look into anyOf subschemas with an not-subschema.

Author: Zac-HD

src/hypothesis_jsonschema/_canonicalise.py

@@ -449,26 +449,33 @@ def canonicalish(schema: JSONType) -> Dict[str, Any]:
     # Canonicalise "not" subschemas
     if "not" in schema:
         not_ = schema.pop("not")
-        if not_ == TRUTHY or not_ == schema:
-            # If everything is rejected, discard all other (irrelevant) keys
-            # TODO: more sensitive detection of cases where the not-clause
-            # excludes everything in the schema.
-            return FALSEY
-        type_keys = {k: set(v.split()) for k, v in TYPE_SPECIFIC_KEYS}
-        type_constraints = {"type"}
-        for v in type_keys.values():
-            type_constraints |= v
-        if set(not_).issubset(type_constraints):
-            not_["type"] = get_type(not_)
-            for t in set(type_).intersection(not_["type"]):
-                if not type_keys.get(t, set()).intersection(not_):
-                    type_.remove(t)
-                    if t not in ("integer", "number"):
-                        not_["type"].remove(t)
-            not_ = canonicalish(not_)
-        if not_ != FALSEY:
-            # If the "not" key rejects nothing, discard it
-            schema["not"] = not_
+
+        negated = []
+        to_negate = not_["anyOf"] if set(not_) == {"anyOf"} else [not_]
+        for not_ in to_negate:
+            type_keys = {k: set(v.split()) for k, v in TYPE_SPECIFIC_KEYS}
+            type_constraints = {"type"}
+            for v in type_keys.values():
+                type_constraints |= v
+            if set(not_).issubset(type_constraints):
+                not_["type"] = get_type(not_)
+                for t in set(type_).intersection(not_["type"]):
+                    if not type_keys.get(t, set()).intersection(not_):
+                        type_.remove(t)
+                        if t not in ("integer", "number"):
+                            not_["type"].remove(t)
+                not_ = canonicalish(not_)
+
+            m = merged([not_, {**schema, "type": type_}])
+            if m is not None:
+                not_ = m
+            if not_ != FALSEY:
+                negated.append(not_)
+        if len(negated) > 1:
+            schema["not"] = {"anyOf": negated}
+        elif negated:
+            schema["not"] = negated[0]
+
     assert isinstance(type_, list), type_
     if not type_:
         assert type_ == []
@@ -490,6 +497,9 @@ def canonicalish(schema: JSONType) -> Dict[str, Any]:
     if TRUTHY in schema.get("anyOf", ()):
         schema.pop("anyOf", None)
     if "anyOf" in schema:
+        for i, s in enumerate(list(schema["anyOf"])):
+            if set(s) == {"anyOf"}:
+                schema["anyOf"][i : i + 1] = s["anyOf"]
         schema["anyOf"] = sorted(schema["anyOf"], key=encode_canonical_json)
         schema["anyOf"] = [s for s in schema["anyOf"] if s != FALSEY]
         if not schema["anyOf"]:

tests/test_canonicalise.py

@@ -101,6 +101,8 @@ def test_canonicalises_to_equivalent_fixpoint(schema_strategy, data):
             "multipleOf": 3,
         },
         {"not": {"type": ["integer", "number"]}, "type": "number"},
+        {"not": {"anyOf": [{"type": "integer"}, {"type": "number"}]}, "type": "number"},
+        {"not": {"enum": [1, 2, 3]}, "const": 2},
         {"oneOf": []},
         {"oneOf": [{}, {}]},
         {"oneOf": [True, False, {}]},
@@ -137,6 +139,7 @@ def test_canonicalises_to_empty(schema):
     [
         ({"type": get_type({})}, {}),
         ({"required": []}, {}),
+        ({"type": "integer", "not": {"type": "string"}}, {"type": "integer"}),
         (
             {"type": "array", "items": [True, False, True]},
             {"type": "array", "items": [{}], "maxItems": 1},
@@ -193,6 +196,16 @@ def test_canonicalises_to_empty(schema):
             {"minItems": 1, "type": "array"},
         ),
         ({"anyOf": [{}, {"type": "null"}]}, {}),
+        (
+            {
+                "anyOf": [
+                    {"type": "string"},
+                    {"anyOf": [{"type": "number"}, {"type": "array"}]},
+                ]
+            },
+            # TODO: collapse into {"type": ["string", "number", "array"]}
+            {"anyOf": [{"type": "array"}, {"type": "number"}, {"type": "string"}]},
+        ),
         ({"uniqueItems": False}, {}),
         (
             {

tox.ini

@@ -59,7 +59,7 @@ addopts =
     --cov-fail-under=100
 
 [flake8]
-ignore = D1,E501,W503,S101,S310
+ignore = D1,E203,E501,W503,S101,S310
 exclude = .*/,__pycache__
 
 [mypy]