Fix #28, avoid infinite loop when the parser can success with no text…

… in nested `many`.

Signed-off-by: HE, Tao <sighingnow@gmail.com>

src/parsec/__init__.py

@@ -418,6 +418,20 @@ def times_parser(text, index):
                     return res  # failed, throw exception.
             if cnt >= maxt:  # finish.
                 break
+            # If we don't have any remaining text to start next loop, we need break.
+            #
+            # We cannot put the `index < len(text)` in where because some parser can
+            # success even when we have no any text. We also need to detect if the
+            # parser consume no text.
+            #
+            # See: #28
+            if index >= len(text):
+                if cnt >= mint:
+                    break  # we already have decent result to return
+                else:
+                    r = p(text, index)
+                    if index != r.index:  # report error when the parser cannot success with no text
+                        return Value.failure(index, "already meets the end, no enough text")
         return values
     return times_parser
 

tests/test_parsec.py

@@ -190,6 +190,16 @@ def test_many(self):
         self.assertEqual(parser.parse(''), [])
         self.assertEqual(parser.parse('1'), [])
 
+    # from #28
+    def test_many_many(self):
+        parser = many(many(space()))
+        self.assertEqual(parser.parse('    '), [[' ', ' ', ' ', ' ']])
+
+        parser = times(spaces(), 4, 10)
+        self.assertEqual(parser.parse(''), [[], [], [], []])
+        self.assertEqual(parser.parse(' '), [[' '], [], [], []])
+        self.assertEqual(parser.parse('  '), [[' ', ' '], [], [], []])
+
     def test_many1(self):
         parser = many1(letter())
         self.assertEqual(parser.parse('x'), ['x'])