Don't leak the additionalItems keyword into JSON Schema draft 202…

…0-12

In 2020-12 it is called 'items', which of course is already supported.

CHANGELOG.rst

@@ -2,6 +2,7 @@ v4.19.2
 =======
 
 * Fix the error message for additional items when used with heterogeneous arrays.
+* Don't leak the ``additionalItems`` keyword into JSON Schema draft 2020-12, where it was replaced by ``items``.
 
 v4.19.1
 =======

jsonschema/_keywords.py

@@ -83,24 +83,6 @@ def items(validator, items, instance, schema):
             )
 
 
-def additionalItems(validator, aI, instance, schema):
-    if (
-        not validator.is_type(instance, "array")
-        or validator.is_type(schema.get("items", {}), "object")
-    ):
-        return
-
-    len_items = len(schema.get("items", []))
-    if validator.is_type(aI, "object"):
-        for index, item in enumerate(instance[len_items:], start=len_items):
-            yield from validator.descend(item, aI, path=index)
-    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", [])):]),
-        )
-
-
 def const(validator, const, instance, schema):
     if not equal(instance, const):
         yield ValidationError(f"{const!r} was expected")

jsonschema/_legacy_keywords.py

@@ -101,6 +101,24 @@ def items_draft3_draft4(validator, items, instance, schema):
             )
 
 
+def additionalItems(validator, aI, instance, schema):
+    if (
+        not validator.is_type(instance, "array")
+        or validator.is_type(schema.get("items", {}), "object")
+    ):
+        return
+
+    len_items = len(schema.get("items", []))
+    if validator.is_type(aI, "object"):
+        for index, item in enumerate(instance[len_items:], start=len_items):
+            yield from validator.descend(item, aI, path=index)
+    elif not aI and len(instance) > len(schema.get("items", [])):
+        error = "Additional items are not allowed (%s %s unexpected)"
+        yield ValidationError(
+            error % _utils.extras_msg(instance[len(schema.get("items", [])):]),
+        )
+
+
 def items_draft6_draft7_draft201909(validator, items, instance, schema):
     if not validator.is_type(instance, "array"):
         return

jsonschema/validators.py

@@ -587,7 +587,7 @@ def extend(
     ),
     validators={
         "$ref": _keywords.ref,
-        "additionalItems": _keywords.additionalItems,
+        "additionalItems": _legacy_keywords.additionalItems,
         "additionalProperties": _keywords.additionalProperties,
         "dependencies": _legacy_keywords.dependencies_draft3,
         "disallow": _legacy_keywords.disallow_draft3,
@@ -621,7 +621,7 @@ def extend(
     ),
     validators={
         "$ref": _keywords.ref,
-        "additionalItems": _keywords.additionalItems,
+        "additionalItems": _legacy_keywords.additionalItems,
         "additionalProperties": _keywords.additionalProperties,
         "allOf": _keywords.allOf,
         "anyOf": _keywords.anyOf,
@@ -660,7 +660,7 @@ def extend(
     ),
     validators={
         "$ref": _keywords.ref,
-        "additionalItems": _keywords.additionalItems,
+        "additionalItems": _legacy_keywords.additionalItems,
         "additionalProperties": _keywords.additionalProperties,
         "allOf": _keywords.allOf,
         "anyOf": _keywords.anyOf,
@@ -704,7 +704,7 @@ def extend(
     ),
     validators={
         "$ref": _keywords.ref,
-        "additionalItems": _keywords.additionalItems,
+        "additionalItems": _legacy_keywords.additionalItems,
         "additionalProperties": _keywords.additionalProperties,
         "allOf": _keywords.allOf,
         "anyOf": _keywords.anyOf,
@@ -750,7 +750,7 @@ def extend(
     validators={
         "$recursiveRef": _legacy_keywords.recursiveRef,
         "$ref": _keywords.ref,
-        "additionalItems": _keywords.additionalItems,
+        "additionalItems": _legacy_keywords.additionalItems,
         "additionalProperties": _keywords.additionalProperties,
         "allOf": _keywords.allOf,
         "anyOf": _keywords.anyOf,
@@ -797,7 +797,6 @@ def extend(
     validators={
         "$dynamicRef": _keywords.dynamicRef,
         "$ref": _keywords.ref,
-        "additionalItems": _keywords.additionalItems,
         "additionalProperties": _keywords.additionalProperties,
         "allOf": _keywords.allOf,
         "anyOf": _keywords.anyOf,