Remove too-tight assertion

Author: Zac-HD

src/hypothesis_jsonschema/_canonicalise.py

@@ -51,7 +51,7 @@
 # Note that in some cases ("dependencies"), the value may be a list of strings.
 SCHEMA_OBJECT_KEYS = ("properties", "patternProperties", "dependencies")
 ALL_KEYWORDS = tuple(
-    ["$schema", *SCHEMA_KEYS, *SCHEMA_OBJECT_KEYS]
+    [*SCHEMA_KEYS, *SCHEMA_OBJECT_KEYS]
     + sum((s.split() for _, s in TYPE_SPECIFIC_KEYS), [])
 )
 
@@ -737,15 +737,26 @@ def merged(schemas: List[Any]) -> Optional[Schema]:
                     out["multipleOf"] = max(x, y)
                 else:
                     return None
-
+        # TODO: merge `contains` schemas when one is a subset of the other
+        # TODO: merge `items` schemas or lists-of-schemas
+        # TODO: merge `not` schemas as {not: anyOf: [not1, not2]}
+        # TODO: merge if/then/else schemas to the chained form
+        #       or maybe canonicalise them to an anyOf instead?
+        # TODO: merge dependencies
+
+        # This loop handles the remaining cases.  Notably, we do not attempt to
+        # merge distinct values for:
+        # - `pattern`; computing regex intersection is out of scope
+        # - `contains`; requires allOf and thus enters an infinite loop
+        # - `$ref`; if not already resolved we can't do that here
+        # - `anyOf`; due to product-like explosion in worst case
+        # - `oneOf`; which we plan to handle as an anyOf-not composition
         for k, v in s.items():
             if k not in out:
                 out[k] = v
             elif out[k] != v and k in ALL_KEYWORDS:
                 # If non-validation keys like `title` or `description` don't match,
                 # that doesn't really matter and we'll just go with first we saw.
-                known = "$ref $schema anyOf oneOf items if not pattern contains"
-                assert k in known.split(), (k, out[k], v)
                 return None
         out = canonicalish(out)
         if out == FALSEY:

tests/test_canonicalise.py

@@ -338,14 +338,6 @@ def test_merged(group, result):
     assert merged(group) == result
 
 
-def test_unable_to_merge_differnt_draft_versions():
-    different_drafts = [
-        {"$schema": "http://json-schema.org/draft-04/schema#"},
-        {"$schema": "http://json-schema.org/draft-07/schema#"},
-    ]
-    assert merged(different_drafts) is None
-
-
 @settings(suppress_health_check=[HealthCheck.too_slow], deadline=None)
 @given(json_schemata())
 def test_self_merge_eq_canonicalish(schema):
@@ -418,6 +410,11 @@ def _canonicalises_to_equivalent_fixpoint(data):
     jsonschema.validators.validator_for(schema).check_schema(schema)
 
 
+def test_canonicalise_is_only_valid_for_schemas():
+    with pytest.raises(InvalidArgument):
+        canonicalish("not a schema")
+
+
 # Expose fuzz targets in a form that FuzzBuzz can understand (no dotted names)
 fuzz_canonical_json_encoding = test_canonical_json_encoding.hypothesis.fuzz_one_input
 fuzz_merge_semantics = test_merge_semantics.hypothesis.fuzz_one_input