B018 to detect useless-statements at all levels (#434)

* add unit test for b018 at all levels

* fix b018 to detect useless statements at all levels

bugbear.py

@@ -370,6 +370,8 @@ def visit(self, node):
         if is_contextful:
             self.contexts.pop()
 
+        self.check_for_b018(node)
+
     def visit_ExceptHandler(self, node):
         if node.type is None:
             self.errors.append(B001(node.lineno, node.col_offset))
@@ -447,7 +449,6 @@ def visit_Call(self, node):
         self.generic_visit(node)
 
     def visit_Module(self, node):
-        self.check_for_b018(node)
         self.generic_visit(node)
 
     def visit_Assign(self, node):
@@ -503,15 +504,13 @@ def visit_FunctionDef(self, node):
         self.check_for_b901(node)
         self.check_for_b902(node)
         self.check_for_b006_and_b008(node)
-        self.check_for_b018(node)
         self.check_for_b019(node)
         self.check_for_b021(node)
         self.check_for_b906(node)
         self.generic_visit(node)
 
     def visit_ClassDef(self, node):
         self.check_for_b903(node)
-        self.check_for_b018(node)
         self.check_for_b021(node)
         self.check_for_b024_and_b027(node)
         self.generic_visit(node)
@@ -1164,31 +1163,30 @@ def check_for_b903(self, node):
         self.errors.append(B903(node.lineno, node.col_offset))
 
     def check_for_b018(self, node):
-        for subnode in node.body:
-            if not isinstance(subnode, ast.Expr):
-                continue
-            if isinstance(
-                subnode.value,
-                (
-                    ast.List,
-                    ast.Set,
-                    ast.Dict,
-                    ast.Tuple,
-                ),
-            ) or (
-                isinstance(subnode.value, ast.Constant)
-                and (
-                    isinstance(subnode.value.value, (int, float, complex, bytes, bool))
-                    or subnode.value.value is None
-                )
-            ):
-                self.errors.append(
-                    B018(
-                        subnode.lineno,
-                        subnode.col_offset,
-                        vars=(subnode.value.__class__.__name__,),
-                    )
+        if not isinstance(node, ast.Expr):
+            return
+        if isinstance(
+            node.value,
+            (
+                ast.List,
+                ast.Set,
+                ast.Dict,
+                ast.Tuple,
+            ),
+        ) or (
+            isinstance(node.value, ast.Constant)
+            and (
+                isinstance(node.value.value, (int, float, complex, bytes, bool))
+                or node.value.value is None
+            )
+        ):
+            self.errors.append(
+                B018(
+                    node.lineno,
+                    node.col_offset,
+                    vars=(node.value.__class__.__name__,),
                 )
+            )
 
     def check_for_b021(self, node):
         if (

tests/b018_nested.py

@@ -0,0 +1,44 @@
+
+X = 1
+False  # bad
+
+
+def func(y):
+    a = y + 1
+    5.5  # bad
+    return a
+
+
+class TestClass:
+    GOOD = [1, 3]
+    [5, 6]  # bad
+
+    def method(self, xx, yy=5):
+        t = (xx,)
+        (yy,)  # bad
+
+        while 1:
+            i = 3
+            4  # bad
+            for n in range(i):
+                j = 5
+                1.5  # bad
+                if j < n:
+                    u = {1, 2}
+                    {4, 5}  # bad
+                elif j == n:
+                    u = {1, 2, 3}
+                    {4, 5, 6}  # bad
+                else:
+                    u = {2, 3}
+                    {4, 6}  # bad
+                    try:
+                        1j  # bad
+                        r = 2j
+                    except Exception:
+                        r = 3j
+                        5  # bad
+                    finally:
+                        4j  # bad
+                        r += 1
+                    return u + t

tests/test_bugbear.py

@@ -331,6 +331,27 @@ def test_b018_modules(self):
         ]
         self.assertEqual(errors, self.errors(*expected))
 
+    def test_b018_nested(self):
+        filename = Path(__file__).absolute().parent / "b018_nested.py"
+        bbc = BugBearChecker(filename=str(filename))
+        errors = list(bbc.run())
+
+        expected = [
+            B018(3, 0, vars=("Constant",)),
+            B018(8, 4, vars=("Constant",)),
+            B018(14, 4, vars=("List",)),
+            B018(18, 8, vars=("Tuple",)),
+            B018(22, 12, vars=("Constant",)),
+            B018(25, 16, vars=("Constant",)),
+            B018(28, 20, vars=("Set",)),
+            B018(31, 20, vars=("Set",)),
+            B018(34, 20, vars=("Set",)),
+            B018(36, 24, vars=("Constant",)),
+            B018(40, 24, vars=("Constant",)),
+            B018(42, 24, vars=("Constant",)),
+        ]
+        self.assertEqual(errors, self.errors(*expected))
+
     def test_b019(self):
         filename = Path(__file__).absolute().parent / "b019.py"
         bbc = BugBearChecker(filename=str(filename))