Fix 868

pycodestyle.py

@@ -46,6 +46,7 @@
 700 statements
 900 syntax error
 """
+import ast
 import bisect
 import configparser
 import inspect
@@ -1193,6 +1194,25 @@ def is_string_literal(line):
         checker_state['seen_non_imports'] = True
 
 
+def _use_ast_to_check_for_lambda_assignment(logical_line):
+    """Check if the line contains a lambda assignment."""
+    if not logical_line:
+        return False
+    try:
+        tree = ast.parse(logical_line)
+    except (SyntaxError, ValueError):
+        return False
+    for node in ast.walk(tree):
+        if isinstance(node, ast.Assign):
+            for target in node.targets:
+                if (
+                    isinstance(target, ast.Name) and  # assigning to a variable
+                    isinstance(node.value, ast.Lambda)  # lambda expression
+                ):
+                    return True
+    return False
+
+
 @register_check
 def compound_statements(logical_line):
     r"""Compound statements (on the same line) are generally
@@ -1228,6 +1248,9 @@ def compound_statements(logical_line):
     found = line.find(':')
     prev_found = 0
     counts = {char: 0 for char in '{}[]()'}
+    if _use_ast_to_check_for_lambda_assignment(line):
+        yield 0, "E731 do not assign a lambda expression, use a def"
+        return
     while -1 < found < last_char:
         update_counts(line[prev_found:found], counts)
         if (
@@ -1236,13 +1259,6 @@ def compound_statements(logical_line):
                 counts['('] <= counts[')'] and  # (annotation)
                 line[found + 1] != '='  # assignment expression
         ):
-            lambda_kw = LAMBDA_REGEX.search(line, 0, found)
-            if lambda_kw:
-                before = line[:lambda_kw.start()].rstrip()
-                if before[-1:] == '=' and before[:-1].strip().isidentifier():
-                    yield 0, ("E731 do not assign a lambda expression, use a "
-                              "def")
-                break
             if STARTSWITH_DEF_REGEX.match(line):
                 yield 0, "E704 multiple statements on one line (def)"
             elif STARTSWITH_INDENT_STATEMENT_REGEX.match(line):

testing/data/E73.py

@@ -1,5 +1,9 @@
 #: E731:1:1
 f = lambda x: 2 * x
+#: E731:1:1
+f = (  # some long comment that forces this to be on a new line
+    lambda x: 731 * x
+)
 #: E731:1:1 E226:1:16
 f = lambda x: 2*x
 #: E731:2:5
@@ -9,6 +13,13 @@
 f = object()
 f.method = lambda: 'Method'
 
+f = (lambda o: o.lower()) if isinstance('a', str) else (lambda o: o)
+
+f = (
+    lambda o: o.lower(),
+    lambda o: o.upper(),
+)
+
 f = {}
 f['a'] = lambda x: x ** 2