B907: fix crash and test failures on py312 (#399)

Author: AlexWaygood

README.rst

@@ -329,6 +329,12 @@ MIT
 Change Log
 ----------
 
+Unreleased
+~~~~~~~~~~
+
+* Fix a crash and several test failures on Python 3.12, all relating to the B907
+  check.
+
 23.6.5
 ~~~~~~
 

bugbear.py

@@ -1245,36 +1245,34 @@ def myunparse(node: ast.AST) -> str:  # pragma: no cover
         current_mark = None
         variable = None
         for value in node.values:
-            # check for quote mark after pre-marked variable
-            if (
-                current_mark is not None
-                and variable is not None
-                and isinstance(value, ast.Constant)
-                and isinstance(value.value, str)
-                and value.value[0] == current_mark
-            ):
-                self.errors.append(
-                    B907(
-                        variable.lineno,
-                        variable.col_offset,
-                        vars=(myunparse(variable.value),),
-                    )
-                )
-                current_mark = variable = None
-                # don't continue with length>1, so we can detect a new pre-mark
-                # in the same string as a post-mark, e.g. `"{foo}" "{bar}"`
-                if len(value.value) == 1:
+            if isinstance(value, ast.Constant) and isinstance(value.value, str):
+                if not value.value:
                     continue
 
-            # detect pre-mark
-            if (
-                isinstance(value, ast.Constant)
-                and isinstance(value.value, str)
-                and value.value[-1] in quote_marks
-            ):
-                current_mark = value.value[-1]
-                variable = None
-                continue
+                # check for quote mark after pre-marked variable
+                if (
+                    current_mark is not None
+                    and variable is not None
+                    and value.value[0] == current_mark
+                ):
+                    self.errors.append(
+                        B907(
+                            variable.lineno,
+                            variable.col_offset,
+                            vars=(myunparse(variable.value),),
+                        )
+                    )
+                    current_mark = variable = None
+                    # don't continue with length>1, so we can detect a new pre-mark
+                    # in the same string as a post-mark, e.g. `"{foo}" "{bar}"`
+                    if len(value.value) == 1:
+                        continue
+
+                # detect pre-mark
+                if value.value[-1] in quote_marks:
+                    current_mark = value.value[-1]
+                    variable = None
+                    continue
 
             # detect variable, if there's a pre-mark
             if (

tests/b907.py

@@ -17,12 +17,12 @@ def foo():
 f'a "{foo()}" b'
 
 # fmt: off
-k = (f'"' # error emitted on this line since all values are assigned the same lineno
+k = (f'"' # Error emitted here on <py312 (all values assigned the same lineno)
      f'{var}'
      f'"'
      f'"')
 
-k = (f'"' # error emitted on this line
+k = (f'"' # error emitted on this line on <py312
      f'{var}'
      '"'
      f'"')

tests/test_bugbear.py

@@ -8,9 +8,6 @@
 from argparse import Namespace
 from pathlib import Path
 
-from hypothesis import HealthCheck, given, settings
-from hypothesmith import from_grammar
-
 from bugbear import (
     B001,
     B002,
@@ -524,43 +521,51 @@ def test_b907(self):
         filename = Path(__file__).absolute().parent / "b907.py"
         bbc = BugBearChecker(filename=str(filename))
         errors = list(bbc.run())
+        py39 = sys.version_info >= (3, 9)
+        py312 = sys.version_info >= (3, 12)
+
+        def on_py312(number):
+            """F-string nodes have column numbers set to 0 on <py312"""
+            return number if py312 else 0
+
         expected = self.errors(
-            B907(8, 0, vars=("var",)),
-            B907(9, 0, vars=("var",)),
-            B907(10, 0, vars=("var",)),
-            B907(12, 0, vars=("var",)),
-            B907(13, 0, vars=("var",)),
-            B907(14, 0, vars=("var",)),
-            B907(16, 0, vars=("'hello'",)),
-            B907(17, 0, vars=("foo()",)),
-            B907(20, 5, vars=("var",)),
-            B907(25, 5, vars=("var",)),
-            B907(31, 0, vars=("var",)),
-            B907(32, 0, vars=("var",)),
-            B907(33, 0, vars=("var",)),
-            B907(33, 0, vars=("var2",)),
-            B907(34, 0, vars=("var",)),
-            B907(34, 0, vars=("var2",)),
-            B907(35, 0, vars=("var",)),
-            B907(35, 0, vars=("var2",)),
-            B907(38, 0, vars=("var2",)),
-            B907(41, 0, vars=("var",)),
-            B907(42, 0, vars=("var.__str__",)),
-            B907(43, 0, vars=("var.__str__.__repr__",)),
-            B907(44, 0, vars=("3 + 5" if sys.version_info >= (3, 9) else "BinOp",)),
-            B907(45, 0, vars=("foo()",)),
-            B907(46, 0, vars=("None",)),
-            B907(47, 0, vars=("..." if sys.version_info >= (3, 9) else "Ellipsis",)),
-            B907(48, 0, vars=("True",)),
-            B907(51, 0, vars=("var",)),
-            B907(52, 0, vars=("var",)),
-            B907(53, 0, vars=("var",)),
-            B907(54, 0, vars=("var",)),
-            B907(57, 0, vars=("var",)),
-            B907(60, 0, vars=("var",)),
-            B907(64, 0, vars=("var",)),
-            B907(66, 0, vars=("var",)),
-            B907(68, 0, vars=("var",)),
+            B907(8, on_py312(9), vars=("var",)),
+            B907(9, on_py312(3), vars=("var",)),
+            B907(10, on_py312(9), vars=("var",)),
+            B907(12, on_py312(9), vars=("var",)),
+            B907(13, on_py312(3), vars=("var",)),
+            B907(14, on_py312(9), vars=("var",)),
+            B907(16, on_py312(5), vars=("'hello'",)),
+            B907(17, on_py312(5), vars=("foo()",)),
+            # Multiline f-strings have lineno changes as well as colno changes on py312+
+            B907(21 if py312 else 20, 7 if py312 else 5, vars=("var",)),
+            B907(26 if py312 else 25, 7 if py312 else 5, vars=("var",)),
+            B907(31, on_py312(12), vars=("var",)),
+            B907(32, on_py312(3), vars=("var",)),
+            B907(33, on_py312(3), vars=("var",)),
+            B907(33, on_py312(29), vars=("var2",)),
+            B907(34, on_py312(3), vars=("var",)),
+            B907(34, on_py312(15), vars=("var2",)),
+            B907(35, on_py312(3), vars=("var",)),
+            B907(35, on_py312(10), vars=("var2",)),
+            B907(38, on_py312(13), vars=("var2",)),
+            B907(41, on_py312(3), vars=("var",)),
+            B907(42, on_py312(3), vars=("var.__str__",)),
+            B907(43, on_py312(3), vars=("var.__str__.__repr__",)),
+            B907(44, on_py312(3), vars=("3 + 5" if py39 else "BinOp",)),
+            B907(45, on_py312(3), vars=("foo()",)),
+            B907(46, on_py312(3), vars=("None",)),
+            B907(47, on_py312(3), vars=("..." if py39 else "Ellipsis",)),
+            B907(48, on_py312(3), vars=("True",)),
+            B907(51, on_py312(3), vars=("var",)),
+            B907(52, on_py312(3), vars=("var",)),
+            B907(53, on_py312(3), vars=("var",)),
+            B907(54, on_py312(3), vars=("var",)),
+            B907(57, on_py312(3), vars=("var",)),
+            B907(60, on_py312(3), vars=("var",)),
+            B907(64, on_py312(5), vars=("var",)),
+            B907(66, on_py312(3), vars=("var",)),
+            B907(68, on_py312(3), vars=("var",)),
         )
         self.assertEqual(errors, expected)
 
@@ -795,13 +800,18 @@ def test_selfclean_test_bugbear(self):
 
 
 class TestFuzz(unittest.TestCase):
-    @settings(suppress_health_check=[HealthCheck.too_slow])
-    @given(from_grammar().map(ast.parse))
-    def test_does_not_crash_on_any_valid_code(self, syntax_tree):
-        # Given any syntatically-valid source code, flake8-bugbear should
-        # not crash.  This tests doesn't check that we do the *right* thing,
-        # just that we don't crash on valid-if-poorly-styled code!
-        BugBearVisitor(filename="<string>", lines=[]).visit(syntax_tree)
+    # TODO: enable this test on py312 once hypothesmith supports py312
+    if sys.version_info < (3, 12):
+        from hypothesis import HealthCheck, given, settings
+        from hypothesmith import from_grammar
+
+        @settings(suppress_health_check=[HealthCheck.too_slow])
+        @given(from_grammar().map(ast.parse))
+        def test_does_not_crash_on_any_valid_code(self, syntax_tree):
+            # Given any syntatically-valid source code, flake8-bugbear should
+            # not crash.  This tests doesn't check that we do the *right* thing,
+            # just that we don't crash on valid-if-poorly-styled code!
+            BugBearVisitor(filename="<string>", lines=[]).visit(syntax_tree)
 
     def test_does_not_crash_on_site_code(self):
         # Because the generator isn't perfect, we'll also test on all the code