Improve performance for conditional keywords

Author: Stranger6667

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Changelog
 
+#### 0.18.2 - 2020-11-22
 - Remove internal caching due to hash collisions (#71)
+- Improve performance for conditional keywords
 
 #### 0.18.1 - 2020-11-21
 - Canonicalise `anyOf` special cases when all subschemas have only the `type` keyword

src/hypothesis_jsonschema/__init__.py

@@ -3,7 +3,7 @@
 The only public API is `from_schema`; check the docstring for details.
 """
 
-__version__ = "0.18.1"
+__version__ = "0.18.2"
 __all__ = ["from_schema"]
 
 from ._from_schema import from_schema

src/hypothesis_jsonschema/_canonicalise.py

@@ -243,12 +243,12 @@ def canonicalish(schema: JSONType) -> Dict[str, Any]:
     then = schema.pop("then", schema)
     else_ = schema.pop("else", schema)
     if if_ is not None and (then is not schema or else_ is not schema):
-        schema = {
-            "anyOf": [
+        if then not in (if_, TRUTHY) or else_ != TRUTHY:
+            alternatives = [
                 {"allOf": [if_, then, schema]},
                 {"allOf": [{"not": if_}, else_, schema]},
             ]
-        }
+            schema = canonicalish({"anyOf": alternatives})
     assert isinstance(schema, dict)
     # Recurse into the value of each keyword with a schema (or list of them) as a value
     for key in SCHEMA_KEYS:

tests/test_canonicalise.py

@@ -260,6 +260,22 @@ def test_canonicalises_to_empty(schema):
             # TODO: could be {"enum": ["a", "b", "c"]},
             {"anyOf": [{"const": "a"}, {"const": "b"}, {"const": "c"}]},
         ),
+        (
+            {"if": {"type": "null"}, "then": {"type": "null"}},
+            {},
+        ),
+        (
+            {"if": {"type": "null"}, "then": {"type": "null"}, "else": {}},
+            {},
+        ),
+        (
+            {"if": {"type": "null"}, "then": {}, "else": {}},
+            {},
+        ),
+        (
+            {"if": {"type": "integer"}, "then": {}, "else": {}, "type": "number"},
+            {"type": "number"},
+        ),
     ],
 )
 def test_canonicalises_to_expected(schema, expected):