basic LR unit test

2 files changed, 33 insertions, 0 deletions

diff --git a/pyparsing/testing.py b/pyparsing/testing.py
index 393f37b..f375290 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._bounded_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._bounded_recursion_enabled = self._save_context["recursion_enabled"]
 
             __compat__.collect_all_And_tokens = self._save_context["__compat__"]
 
diff --git a/tests/test_unit.py b/tests/test_unit.py
index 09ad6a4..2ec771e 100644
--- a/tests/test_unit.py
+++ b/tests/test_unit.py
@@ -8067,9 +8067,39 @@ class Test8_WithUnboundedPackrat(Test2_WithoutPackrat):
         )
 
 
+class TestLR1_Recursion(ppt.TestParseResultsAsserts, TestCase):
+    """
+    Tests for recursive parsing
+    """
+    suite_context = None
+    save_suite_context = None
+
+    def setUp(self):
+        recursion_suite_context.restore()
+
+    def test_binary_recursive(self):
+        """Parsing single left-recursive binary operator"""
+        expr = pp.Forward("expr")
+        num = pp.Word(pp.nums)
+        expr <<= expr + '+' - num | num
+        self.assertParseResultsEquals(
+            expr.parseString("1+2"),
+            expected_list=['1', '+', '2']
+        )
+        self.assertParseResultsEquals(
+            expr.parseString("1+2+3+4"),
+            expected_list=['1', '+', '2', '+', '3', '+', '4']
+        )
+
+
 # force clear of packrat parsing flags before saving contexts
 pp.ParserElement._packratEnabled = False
 pp.ParserElement._parse = pp.ParserElement._parseNoCache
 
 Test2_WithoutPackrat.suite_context = ppt.reset_pyparsing_context().save()
 Test2_WithoutPackrat.save_suite_context = ppt.reset_pyparsing_context().save()
+
+default_suite_context = ppt.reset_pyparsing_context().save()
+pp.ParserElement.enable_bounded_recursion()
+recursion_suite_context = ppt.reset_pyparsing_context().save()
+default_suite_context.restore()