Fix tokenizer: Dedents before error tokens are properly done, now.

parso/python/tokenize.py

@@ -364,6 +364,14 @@ def tokenize_lines(lines, version_info, start_pos=(1, 0)):
     token. This idea comes from lib2to3. The prefix contains all information
     that is irrelevant for the parser like newlines in parentheses or comments.
     """
+    def dedent_if_necessary(start):
+        while start < indents[-1]:
+            if start > indents[-2]:
+                yield PythonToken(ERROR_DEDENT, '', (lnum, 0), '')
+                break
+            yield PythonToken(DEDENT, '', spos, '')
+            indents.pop()
+
     pseudo_token, single_quoted, triple_quoted, endpats, whitespace, \
         fstring_pattern_map, always_break_tokens, = \
         _get_token_collection(version_info)
@@ -450,6 +458,9 @@ def tokenize_lines(lines, version_info, start_pos=(1, 0)):
             if not pseudomatch:                             # scan for tokens
                 match = whitespace.match(line, pos)
                 pos = match.end()
+                new_line = False
+                for t in dedent_if_necessary(pos):
+                    yield t
                 yield PythonToken(
                     ERRORTOKEN, line[pos], (lnum, pos),
                     additional_prefix + match.group(0)
@@ -482,12 +493,8 @@ def tokenize_lines(lines, version_info, start_pos=(1, 0)):
                     if start > indents[-1]:
                         yield PythonToken(INDENT, '', spos, '')
                         indents.append(start)
-                    while start < indents[-1]:
-                        if start > indents[-2]:
-                            yield PythonToken(ERROR_DEDENT, '', (lnum, 0), '')
-                            break
-                        yield PythonToken(DEDENT, '', spos, '')
-                        indents.pop()
+                    for t in dedent_if_necessary(start):
+                        yield t
 
             if fstring_stack:
                 fstring_index, end = _check_fstring_ending(fstring_stack, token)

test/test_diff_parser.py

@@ -935,5 +935,20 @@ def test_with_and_funcdef_in_call(differ, prefix):
     code2 = insert_line_into_code(code1, 3, 'def y(self, args):\n')
 
     differ.initialize(code1)
-    differ.parse(code2, parsers=3, copies=0, expect_error_leaves=True)
-    differ.parse(code1, parsers=1, copies=0)
+    differ.parse(code2, parsers=3, expect_error_leaves=True)
+    differ.parse(code1, parsers=1)
+
+
+def test_wrong_backslash(differ):
+    code1 = dedent('''\
+        def y():
+            1
+            for x in y:
+                continue
+        ''')
+
+    code2 = insert_line_into_code(code1, 3, '\.whl$\n')
+
+    differ.initialize(code1)
+    differ.parse(code2, parsers=2, copies=2, expect_error_leaves=True)
+    differ.parse(code1, parsers=1, copies=1)

test/test_tokenize.py

@@ -197,11 +197,12 @@ def test_ur_literals():
 
 
 def test_error_literal():
-    error_token, endmarker = _get_token_list('"\n')
+    error_token, newline, endmarker = _get_token_list('"\n')
     assert error_token.type == ERRORTOKEN
     assert error_token.string == '"'
+    assert newline.type == NEWLINE
     assert endmarker.type == ENDMARKER
-    assert endmarker.prefix == '\n'
+    assert endmarker.prefix == ''
 
     bracket, error_token, endmarker = _get_token_list('( """')
     assert error_token.type == ERRORTOKEN
@@ -240,11 +241,12 @@ def test_indentation(code, types):
 
 
 def test_error_string():
-    t1, endmarker = _get_token_list(' "\n')
+    t1, newline, endmarker = _get_token_list(' "\n')
     assert t1.type == ERRORTOKEN
     assert t1.prefix == ' '
     assert t1.string == '"'
-    assert endmarker.prefix == '\n'
+    assert newline.type == NEWLINE
+    assert endmarker.prefix == ''
     assert endmarker.string == ''
 
 
@@ -268,3 +270,18 @@ def test_indent_error_recovery():
         # `b`
         NAME, NEWLINE, ENDMARKER]
     assert [t.type for t in lst] == expected
+
+
+def test_error_token_after_dedent():
+    code = dedent("""\
+        class C:
+            pass
+        $foo
+        """)
+    lst = _get_token_list(code)
+    expected = [
+        NAME, NAME, OP, NEWLINE, INDENT, NAME, NEWLINE, DEDENT,
+        # $foo\n
+        ERRORTOKEN, NAME, NEWLINE, ENDMARKER
+    ]
+    assert [t.type for t in lst] == expected