Allow using '$defs' keyword

json-schema 2019.09 standardized '$defs' keyword for reusable schema
fragments. Let's allow it to be used in schemas.

Signed-off-by: Rob Herring <[email protected]>

Author: robherring

dtschema/lib.py

@@ -344,7 +344,7 @@ def fixup_schema(schema):
             for prop in v:
                 fixup_schema(v[prop])
 
-        if not k in ['properties', 'patternProperties']:
+        if not k in ['properties', 'patternProperties', '$defs']:
             continue
 
         walk_properties(v)

meta-schemas/base.yaml

@@ -42,6 +42,7 @@ properties:
   anyOf: true
   oneOf: true
   definitions: true
+  $defs: true
   additionalProperties: true
   dependencies: true
   patternProperties: true

meta-schemas/keywords.yaml

@@ -94,6 +94,7 @@ properties:
     $ref: "#/definitions/sub-schemas"
   const: true
   default: true
+  $defs: true
   definitions: true
   dependencies: true
   deprecated: true