Fix valid_name regex for SLexer

This fixes #1331
All modifications to regex:
1. Delete 2 useless non-capturing groups
2. Variables can not start with underscore (_)
3. Only letters, dot (.) and underscore (_) can go after first dot (.) in name
4. Name from only one symbol dot (.) is possible

1 files changed, 37 insertions, 0 deletions

diff --git a/tests/test_r.py b/tests/test_r.py
index 72cb8afc..6dcc78e3 100644
--- a/tests/test_r.py
+++ b/tests/test_r.py
@@ -73,3 +73,40 @@ def test_custom_operator(lexer):
         (Token.Text, u'\n'),
     ]
     assert list(lexer.get_tokens(fragment)) == tokens
+
+
+def test_indexing(lexer):
+    fragment = u'a[1]'
+    tokens = [
+        (Token.Name, u'a'),
+        (Token.Punctuation, u'['),
+        (Token.Literal.Number, u'1'),
+        (Token.Punctuation, u']'),
+        (Token.Text, u'\n'),
+    ]
+    assert list(lexer.get_tokens(fragment)) == tokens
+
+
+def test_dot_name(lexer):
+    fragment = u'. <- 1'
+    tokens = [
+        (Token.Name, '.'),
+        (Token.Text, ' '),
+        (Token.Operator, '<-'),
+        (Token.Text, ' '),
+        (Token.Literal.Number, '1'),
+        (Token.Text, '\n')
+    ]
+    assert list(lexer.get_tokens(fragment)) == tokens
+
+
+def test_dot_indexing(lexer):
+    fragment = u'.[1]'
+    tokens = [
+        (Token.Name, u'.'),
+        (Token.Punctuation, u'['),
+        (Token.Literal.Number, u'1'),
+        (Token.Punctuation, u']'),
+        (Token.Text, u'\n'),
+    ]
+    assert list(lexer.get_tokens(fragment)) == tokens