Make the JSON parser fast again

examples/json_parser.py

@@ -49,11 +49,21 @@ class TreeToJson(Transformer):
     false = lambda self, _: False
 
 
+### Create the JSON parser with Lark, using the Earley algorithm
 # json_parser = Lark(json_grammar, parser='earley', lexer='standard')
 # def parse(x):
 #     return TreeToJson().transform(json_parser.parse(x))
 
-json_parser = Lark(json_grammar, parser='lalr', lexer='standard', transformer=TreeToJson())
+### Create the JSON parser with Lark, using the LALR algorithm
+json_parser = Lark(json_grammar, parser='lalr',
+                   # Using the standard lexer isn't required, and isn't usually recommended.
+                   # But, it's good enough for JSON, and it's slightly faster.
+                   lexer='standard',
+                   # Disabling propagate_positions and placeholders slightly improves speed
+                   propagate_positions=False,
+                   maybe_placeholders=False,
+                   # Using an internal transformer is faster and more memory efficient
+                   transformer=TreeToJson())
 parse = json_parser.parse