Add support for slice in expr[] notation, to pass stop_on repetition sentinel

4 files changed, 48 insertions, 12 deletions

diff --git a/CHANGES b/CHANGES
index d2af488..ac542a3 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4,6 +4,19 @@ Change Log
 
 Version 3.0.10 - (in development)
 ---------------------------------
+- Extended `expr[]` notation to accept a slice, indicating a `stop_on`
+  expression:
+
+      test = "BEGIN aaa bbb ccc END"
+      BEGIN, END = map(Keyword, "BEGIN END".split())
+      body_word = Word(alphas)
+      expr = BEGIN + Group(body_word[...: END]) + END
+      print(expr.parse_string(test).as_list())
+
+  Prints:
+
+      ['BEGIN', ['aaa', 'bbb', 'ccc'], 'END']
+
 - Fixed bug in srange, when parsing escaped '/' and '\' inside a
   range set.
 
diff --git a/pyparsing/__init__.py b/pyparsing/__init__.py
index b2333ee..485f471 100644
--- a/pyparsing/__init__.py
+++ b/pyparsing/__init__.py
@@ -129,7 +129,7 @@ class version_info(NamedTuple):
 
 
 __version_info__ = version_info(3, 0, 10, "final", 0)
-__version_time__ = "14 May 2022 07:35 UTC"
+__version_time__ = "19 May 2022 04:43 UTC"
 __version__ = __version_info__.__version__
 __versionTime__ = __version_time__
 __author__ = "Paul McGuire <ptmcg.gm+pyparsing@gmail.com>"
diff --git a/pyparsing/core.py b/pyparsing/core.py
index 13ff51b..4638d19 100644
--- a/pyparsing/core.py
+++ b/pyparsing/core.py
@@ -1639,8 +1639,23 @@ class ParserElement(ABC):
         Note that ``expr[..., n]`` and ``expr[m, n]``do not raise an exception
         if more than ``n`` ``expr``s exist in the input stream.  If this behavior is
         desired, then write ``expr[..., n] + ~expr``.
+
+        For repetition with a stop_on expression, use slice notation:
+
+        - ``expr[...: end_expr]`` and ``expr[0, ...: end_expr]`` are equivalent to ``ZeroOrMore(expr, stop_on=end_expr)``
+        - ``expr[1, ...: end_expr]`` is equivalent to ``OneOrMore(expr, stop_on=end_expr)``
+
         """
 
+        stop_on_defined = False
+        stop_on = NoMatch()
+        if isinstance(key, slice):
+            key, stop_on = key.start, key.stop
+            stop_on_defined = True
+        elif isinstance(key, tuple) and isinstance(key[-1], slice):
+            key, stop_on = (key[0], key[1].start), key[1].stop
+            stop_on_defined = True
+
         # convert single arg keys to tuples
         try:
             if isinstance(key, str_type):
@@ -1658,6 +1673,11 @@ class ParserElement(ABC):
 
         # clip to 2 elements
         ret = self * tuple(key[:2])
+        ret = typing.cast(_MultipleMatch, ret)
+
+        if stop_on_defined:
+            ret.stopOn(stop_on)
+
         return ret
 
     def __call__(self, name: str = None) -> "ParserElement":
diff --git a/tests/test_unit.py b/tests/test_unit.py
index e11524f..c070c52 100644
--- a/tests/test_unit.py
+++ b/tests/test_unit.py
@@ -5728,10 +5728,14 @@ class Test02_WithoutPackrat(ppt.TestParseResultsAsserts, TestCase):
                 expr, test, "Did not successfully stop on ending expression %r" % ender
             )
 
-            expr = BEGIN + body_word[...].stopOn(ender) + END
-            self.assertEqual(
-                expr, test, "Did not successfully stop on ending expression %r" % ender
-            )
+            expr = BEGIN + body_word[1, ...].stopOn(ender) + END
+            self.assertParseAndCheckList(expr, test, test.split(), "Did not successfully stop on ending expression %r" % ender)
+
+            expr = BEGIN + body_word[1, ...: ender] + END
+            self.assertParseAndCheckList(expr, test, test.split(), "Did not successfully stop on ending expression %r" % ender)
+
+            expr = BEGIN + body_word[(1, ...): ender] + END
+            self.assertParseAndCheckList(expr, test, test.split(), "Did not successfully stop on ending expression %r" % ender)
 
         number = pp.Word(pp.nums + ",.()").setName("number with optional commas")
         parser = pp.OneOrMore(pp.Word(pp.alphanums + "-/."), stopOn=number)(
@@ -5751,14 +5755,13 @@ class Test02_WithoutPackrat(ppt.TestParseResultsAsserts, TestCase):
         body_word = pp.Word(pp.alphas).setName("word")
         for ender in (END, "END", pp.CaselessKeyword("END")):
             expr = BEGIN + pp.ZeroOrMore(body_word, stopOn=ender) + END
-            self.assertEqual(
-                expr, test, "Did not successfully stop on ending expression %r" % ender
-            )
+            self.assertParseAndCheckList(expr, test, test.split(), "Did not successfully stop on ending expression %r" % ender)
 
-            expr = BEGIN + body_word[0, ...].stopOn(ender) + END
-            self.assertEqual(
-                expr, test, "Did not successfully stop on ending expression %r" % ender
-            )
+            expr = BEGIN + body_word[...].stopOn(ender) + END
+            self.assertParseAndCheckList(expr, test, test.split(), "Did not successfully stop on ending expression %r" % ender)
+
+            expr = BEGIN + body_word[...: ender] + END
+            self.assertParseAndCheckList(expr, test, test.split(), "Did not successfully stop on ending expression %r" % ender)
 
     def testNestedAsDict(self):