Fix the schema path used by prefixItems errors.

Also simplify its implementation, what it's doing is just zip.

Author: Julian

jsonschema/_validators.py

@@ -97,8 +97,7 @@ def additionalItems(validator, aI, instance, schema):
     elif not aI and len(instance) > len(schema.get("items", [])):
         error = "Additional items are not allowed (%s %s unexpected)"
         yield ValidationError(
-            error %
-            extras_msg(instance[len(schema.get("items", [])):]),
+            error % extras_msg(instance[len(schema.get("items", [])):]),
         )
 
 
@@ -450,7 +449,5 @@ def prefixItems(validator, prefixItems, instance, schema):
     if not validator.is_type(instance, "array"):
         return
 
-    for k, v in enumerate(instance[:min(len(prefixItems), len(instance))]):
-        yield from validator.descend(
-            v, prefixItems[k], schema_path="prefixItems",
-        )
+    for (index, each), subschema in zip(enumerate(instance), prefixItems):
+        yield from validator.descend(each, subschema, schema_path=index)

jsonschema/tests/test_validators.py

@@ -418,7 +418,7 @@ def test_maxItems(self):
         message = self.message_for(instance=[1, 2, 3], schema={"maxItems": 2})
         self.assertEqual(message, "[1, 2, 3] is too long")
 
-    def test_prefixItems(self):
+    def test_prefixItems_with_items(self):
         message = self.message_for(
             instance=[1, 2, "foo", 5],
             schema={"items": False, "prefixItems": [{}, {}]},
@@ -1114,6 +1114,55 @@ def test_ref(self):
             ),
         )
 
+    def test_prefixItems(self):
+        schema = {"prefixItems": [{"type": "string"}, {}, {}, {"maximum": 3}]}
+        validator = validators.Draft202012Validator(schema)
+        type_error, min_error = validator.iter_errors([1, 2, "foo", 5])
+        self.assertEqual(
+            (
+                type_error.message,
+                type_error.validator,
+                type_error.validator_value,
+                type_error.instance,
+                type_error.absolute_path,
+                type_error.schema,
+                type_error.schema_path,
+                type_error.json_path,
+            ),
+            (
+                "1 is not of type 'string'",
+                "type",
+                "string",
+                1,
+                deque([]),
+                {"type": "string"},
+                deque(["prefixItems", 0, "type"]),
+                "$",
+            ),
+        )
+        self.assertEqual(
+            (
+                min_error.message,
+                min_error.validator,
+                min_error.validator_value,
+                min_error.instance,
+                min_error.absolute_path,
+                min_error.schema,
+                min_error.schema_path,
+                min_error.json_path,
+            ),
+            (
+                "5 is greater than the maximum of 3",
+                "maximum",
+                3,
+                5,
+                deque([]),
+                {"maximum": 3},
+                deque(["prefixItems", 3, "maximum"]),
+                "$",
+            ),
+        )
+
 
 class MetaSchemaTestsMixin(object):
     # TODO: These all belong upstream