Use Lark with its cache feature, instead of creating a standalone parser

hcl2/parser.py

@@ -8,46 +8,12 @@
 
 from hcl2.transformer import DictTransformer
 
-PARSER_FILE = os.path.join(dirname(__file__), 'lark_parser.py')
-
-PARSER_FILE_TEMPLATE = """
-from lark import Lark
-
-DATA = (%s)
-MEMO = (%s)
-
-def Lark_StandAlone(**kwargs):
- return Lark._load_from_dict(DATA, MEMO, **kwargs)
-"""
-
-
-def create_parser_file():
- """
- Parsing the Lark grammar takes about 0.5 seconds. In order to improve performance we can cache the parser
- file. The below code caches the entire python file which is generated by Lark's standalone parser feature
- See: https://github.com/lark-parser/lark/blob/master/lark/tools/standalone.py
-
- Lark also supports serializing the parser config but the deserialize function did not work for me.
- The lark state contains dicts with numbers as keys which is not supported by json so the serialized
- state can't be written to a json file. Exporting to other file types would have required
- adding additional dependencies or writing a lot more code. Lark's standalone parser
- feature works great but it expects to be run as a separate shell command
- The below code copies some of the standalone parser generator code in a way that we can use
- """
- lark_file = os.path.join(dirname(__file__), 'hcl2.lark')
- with open(lark_file, 'r') as lark_file, open(PARSER_FILE, 'w') as parser_file:
- lark_inst = Lark(lark_file.read(), parser="lalr", lexer="standard")
-
- data, memo = lark_inst.memo_serialize([TerminalDef, Rule])
-
- print(PARSER_FILE_TEMPLATE % (data, memo), file=parser_file)
-
-
-if not exists(PARSER_FILE):
- create_parser_file()
-
-# pylint: disable=wrong-import-position
-# Lark_StandAlone needs to be imported after the above block of code because lark_parser.py might not exist
-from hcl2.lark_parser import Lark_StandAlone
-
-hcl2 = Lark_StandAlone(transformer=DictTransformer())
+PARSER_FILE = os.path.join(dirname(__file__), '.lark_cache.bin')
+
+hcl2 = Lark.open(
+ 'hcl2.lark',
+ parser='lalr',
+ cache=PARSER_FILE, # Disable/Delete file to effect changes to the grammar
+ rel_to=__file__,
+ transformer=DictTransformer()
+)

requirements.pip

@@ -1,3 +1,3 @@
 # Place dependencies in this file, following the distutils format:
 # http://docs.python.org/2/distutils/setupscript.html#relationships-between-distributions-and-packages
-lark-parser>=0.10.0,<0.11.0
+lark-parser>=0.11.0,<0.12.0

test/unit/test_load.py

@@ -1,11 +1,11 @@
 """ Test parsing a variety of hcl files"""
+
 import json
 import os
 from os.path import dirname
 from unittest import TestCase
 
 import hcl2
-from hcl2.parser import PARSER_FILE, create_parser_file
 
 HCL2_DIR = 'terraform-config'
 JSON_DIR = 'terraform-config-json'
@@ -21,8 +21,6 @@ def setUp(self):
  def test_load_terraform(self):
  """Test parsing a set of hcl2 files and force recreating the parser file"""
  # delete the parser file to force it to be recreated
- os.remove(os.path.join(dirname(hcl2.__file__), PARSER_FILE))
- create_parser_file()
  self._load_test_files()
 
  def test_load_terraform_from_cache(self):