Add support for LR parsingleft_recursion_support

* first draft of LR parsing
* removed debug output
* cache is owned and cleared by ParserElement
* bounded recursion must be enabled explicitly
* packrat rejects recursion
* basic LR unit test
* tests for associativity and nesting
* added math example
* fixed test typo
* unittest for empty and non-peg clauses
* LR-Forward can match Empty
* fixed test typos
* added base case to unittest
* memo cache only provides copies
* flattened Forward parse method
* added high-level description of algorithm
* expanded docstring
* added tests for repetition rules
* renamed bounded to left recursion
* naive test for existing suite
* explicitly testing tests for LR compatibility
* LR memo no longer mixes action/no-action results
* simplified replacement logic
* adjusted example with ambiguous failure case
* LR memo content is always returned as copy
* draft for peeking recursion
* memo update consistent for all actions
* fixed a bug for non-string token identifiers
* action wins against no-action
* cleanup
* properly setting names in tests
* memoization can be turned off
* testing memo switches
* typos
* flattened recursion memo
* left recursion memo size may be limited
* adjusted docs for recursion cache

1 files changed, 3 insertions, 0 deletions

diff --git a/pyparsing/testing.py b/pyparsing/testing.py
index 393f37b..43f23ab 100644
--- a/pyparsing/testing.py
+++ b/pyparsing/testing.py
@@ -20,6 +20,7 @@ class pyparsing_test:
         """
         Context manager to be used when writing unit tests that modify pyparsing config values:
          - packrat parsing
+         - bounded recursion parsing
          - default whitespace characters.
          - default keyword characters
          - literal string auto-conversion class
@@ -61,6 +62,7 @@ class pyparsing_test:
             else:
                 self._save_context["packrat_cache_size"] = None
             self._save_context["packrat_parse"] = ParserElement._parse
+            self._save_context["recursion_enabled"] = ParserElement._left_recursion_enabled
 
             self._save_context["__diag__"] = {
                 name: getattr(__diag__, name) for name in __diag__._all_names
@@ -97,6 +99,7 @@ class pyparsing_test:
                 ParserElement.enablePackrat(self._save_context["packrat_cache_size"])
             else:
                 ParserElement._parse = self._save_context["packrat_parse"]
+            ParserElement._left_recursion_enabled = self._save_context["recursion_enabled"]
 
             __compat__.collect_all_And_tokens = self._save_context["__compat__"]