usage of .css()[0].extract() instead of .extract_first()/.get()

finders/oldstyle.py

@@ -95,3 +95,22 @@ def find_issues(self, node):
         for kw in node.value.keywords:
             if self.has_response_for_keyword_parameter(kw):
                 return [(node.lineno, node.col_offset, self.message)]
+
+
+class GetFirstByIndexIssueFinder(IssueFinder):
+    msg_code = 'SCP06'
+    msg_info = 'use .get() or .extract_first() to get the first item'
+
+    def find_issues(self, node):
+        issue_exists = (
+            node.slice.value.n == 0 and
+            isinstance(node.value, ast.Call) and
+            isinstance(node.value.func, ast.Attribute) and
+            node.value.func.attr == 'extract' and
+            node.value.func.attr in ('css', 'xpath')
+        )
+        if not issue_exists:
+            return
+
+        return [(node.lineno, node.col_offset, self.message)]
+

flake8_scrapy.py

@@ -3,7 +3,9 @@
 from finders.domains import (
     UnreachableDomainIssueFinder, UrlInAllowedDomainsIssueFinder,
 )
-from finders.oldstyle import OldSelectorIssueFinder, UrlJoinIssueFinder
+from finders.oldstyle import (
+    GetFirstByIndexIssueFinder, OldSelectorIssueFinder, UrlJoinIssueFinder,
+)
 
 
 __version__ = '0.0.1'
@@ -22,7 +24,10 @@ def __init__(self, *args, **kwargs):
             ],
             'Call': [
                 UrlJoinIssueFinder(),
-            ]
+            ],
+            'Subscript': [
+                GetFirstByIndexIssueFinder(),
+            ],
         }
 
     def find_issues_visitor(self, visitor, node):
@@ -40,6 +45,9 @@ def visit_Assign(self, node):
     def visit_Call(self, node):
         self.find_issues_visitor('Call', node)
 
+    def visit_Subscript(self, node):
+        self.find_issues_visitor('Subscript', node)
+
 
 class ScrapyStyleChecker(object):
     options = None

tests/test_oldstyle.py

@@ -38,3 +38,16 @@ def test_dont_find_old_style_urljoin(code):
 def test_find_old_style_selector(code, expected):
     issues = run_checker(code)
     assert len(issues) == expected
+
+
+@pytest.mark.parametrize('code,expected', [
+    ('response.css("*")[0].extract()', 1),
+    ('response.xpath("//*")[0].extract()', 1),
+    # ('response.css("*").extract()[0]', 1),
+    # ('response.xpath("//*").extract()[0]', 1),
+    # ('response.css("*").getall()[0]', 1),
+    # ('response.xpath("//*")[0].get()', 1),
+])
+def test_find_oldstyle_get_first_by_index(code, expected):
+    issues = run_checker(code)
+    assert len(issues) == expected