[lexical-scoping] Support root-node reference.

Author: springcomp

jmespath.test

@@ -18,7 +18,6 @@ class Lexer(object):
         ',': 'comma',
         ':': 'colon',
         '@': 'current',
-        '$': 'root',
         '(': 'lparen',
         ')': 'rparen',
         '{': 'lbrace',
@@ -117,7 +116,13 @@ def tokenize(self, expression, options=None):
             elif self._current == '=':
                 yield self._match_or_else('=', 'eq', 'assign')
             elif self._current == '$':
-                yield self._consume_variable()
+                if self._peek_may_be_valid_unquoted_identifier():
+                    yield self._consume_variable()
+                else:
+                    yield {'type': 'root',
+                           'value': self._current,
+                           'start': self._position, 'end': self._position + 1}
+                    self._next()
             else:
                 raise LexerError(lexer_position=self._position,
                                  lexer_value=self._current,
@@ -147,6 +152,13 @@ def _consume_variable(self):
         return {'type': 'variable', 'value': buff,
                 'start': start, 'end': start + len(buff)}
 
+    def _peek_may_be_valid_unquoted_identifier(self):
+        if (self._position == self._length - 1):
+            return False
+        else:
+            next = self._chars[self._position + 1]
+            return next in self.START_IDENTIFIER
+
     def _peek_is_next_digit(self):
         if (self._position == self._length - 1):
             return False

jmespath/lexer.py

@@ -210,6 +210,17 @@ def test_root_reference(self):
             ]
         )
 
+    def test_variable(self):
+        tokens = list(self.lexer.tokenize('$foo'))
+        self.assertEqual(
+            tokens,
+            [{'type': 'variable', 'value': '$foo',
+              'start': 0, 'end': 4},
+            {'type': 'eof', 'value': '',
+                'start': 4, 'end': 4}
+              ]
+        )
+
     def test_unknown_character(self):
         with self.assertRaises(LexerError) as e:
             tokens = list(self.lexer.tokenize('foo[0^]'))

tests/compliance/letexpr.json

@@ -92,7 +92,6 @@ def test_arithmetic_expressions(self):
         for sign in operations:
             operation = operations[sign]
             expression = 'foo {} bar'.format(sign)
-            print(expression)
             self.assert_parsed_ast(
                 expression,
                 ast.arithmetic(
@@ -110,7 +109,6 @@ def test_arithmetic_unary(self):
         for sign in operations:
             operation = operations[sign]
             expression = '{} foo'.format(sign)
-            print(expression)
             self.assert_parsed_ast(
                 expression,
                 ast.arithmetic_unary(