[multiple-statements] Make pylint compatible with black's 2024 style (#9697)

* Add more test cases to cover pass / ...
* Define the confidence as HIGH
* Exclude the class with Ellipsis from the check

Closes #9398

Author: Pierre-Sassoulas

doc/whatsnew/fragments/9398.false_positive

@@ -0,0 +1,4 @@
+Classes with only an Ellipsis (``...``) in their body do not trigger 'multiple-statements'
+anymore if they are inlined (in accordance with black's 2024 style).
+
+Closes #9398

pylint/checkers/format.py

@@ -522,9 +522,8 @@ def visit_default(self, node: nodes.NodeNG) -> None:
 
     def _check_multi_statement_line(self, node: nodes.NodeNG, line: int) -> None:
         """Check for lines containing multiple statements."""
-        # Do not warn about multiple nested context managers
-        # in with statements.
         if isinstance(node, nodes.With):
+            # Do not warn about multiple nested context managers in with statements.
             return
         if (
             isinstance(node.parent, nodes.If)
@@ -539,16 +538,16 @@ def _check_multi_statement_line(self, node: nodes.NodeNG, line: int) -> None:
         ):
             return
 
-        # Functions stubs with ``Ellipsis`` as body are exempted.
+        # Functions stubs and class with ``Ellipsis`` as body are exempted.
         if (
-            isinstance(node.parent, nodes.FunctionDef)
-            and isinstance(node, nodes.Expr)
+            isinstance(node, nodes.Expr)
+            and isinstance(node.parent, (nodes.FunctionDef, nodes.ClassDef))
             and isinstance(node.value, nodes.Const)
             and node.value.value is Ellipsis
         ):
             return
 
-        self.add_message("multiple-statements", node=node)
+        self.add_message("multiple-statements", node=node, confidence=HIGH)
         self._visited_lines[line] = 2
 
     def check_trailing_whitespace_ending(self, line: str, i: int) -> None:

tests/functional/m/multiple_statements.py

@@ -4,13 +4,28 @@
 
 from typing import overload
 
+if True: print("Golfing sure is nice")  # [multiple-statements]
 if True: pass  # [multiple-statements]
+if True: ...  # [multiple-statements]
+
+if True: print("Golfing sure is nice")  # [multiple-statements]
+else:
+    pass
 
 if True: pass  # [multiple-statements]
 else:
     pass
 
+if True: ...  # [multiple-statements]
+else:
+    pass
+
+# The following difference in behavior is due to black 2024's style
+# that reformat pass on multiple line but reformat "..." on a single line
+# (only for classes, not for the examples above)
+class MyException(Exception): print("Golfing sure is nice")  # [multiple-statements]
 class MyError(Exception): pass  # [multiple-statements]
+class DebugTrueDetected(Exception): ...
 
 class MyError(Exception): a='a'  # [multiple-statements]
 

tests/functional/m/multiple_statements.txt

@@ -1,5 +1,10 @@
-multiple-statements:7:9:7:13::More than one statement on a single line:UNDEFINED
-multiple-statements:9:9:9:13::More than one statement on a single line:UNDEFINED
-multiple-statements:13:26:13:30:MyError:More than one statement on a single line:UNDEFINED
-multiple-statements:15:26:15:31:MyError:More than one statement on a single line:UNDEFINED
-multiple-statements:17:26:17:31:MyError:More than one statement on a single line:UNDEFINED
+multiple-statements:7:9:7:38::More than one statement on a single line:HIGH
+multiple-statements:8:9:8:13::More than one statement on a single line:HIGH
+multiple-statements:9:9:9:12::More than one statement on a single line:HIGH
+multiple-statements:11:9:11:38::More than one statement on a single line:HIGH
+multiple-statements:15:9:15:13::More than one statement on a single line:HIGH
+multiple-statements:19:9:19:12::More than one statement on a single line:HIGH
+multiple-statements:26:30:26:59:MyException:More than one statement on a single line:HIGH
+multiple-statements:27:26:27:30:MyError:More than one statement on a single line:HIGH
+multiple-statements:30:26:30:31:MyError:More than one statement on a single line:HIGH
+multiple-statements:32:26:32:31:MyError:More than one statement on a single line:HIGH

tests/functional/m/multiple_statements_single_line.py

@@ -4,19 +4,32 @@
 
 from typing import overload
 
+if True: print("Golfing sure is nice")
 if True: pass
+if True: ...
+
+if True: print("Golfing sure is nice")  # [multiple-statements]
+else:
+    pass
 
 if True: pass  # [multiple-statements]
 else:
     pass
 
+if True: ...  # [multiple-statements]
+else:
+    pass
+
+class MyException(Exception): print("Golfing sure is nice")
 class MyError(Exception): pass
+class DebugTrueDetected(Exception): ...
+
 
 class MyError(Exception): a='a'
 
 class MyError(Exception): a='a'; b='b'  # [multiple-statements]
 
-try:
+try:  #@
     pass
 except:
     pass

tests/functional/m/multiple_statements_single_line.txt

@@ -1,2 +1,4 @@
-multiple-statements:9:9:9:13::More than one statement on a single line:UNDEFINED
-multiple-statements:17:26:17:31:MyError:More than one statement on a single line:UNDEFINED
+multiple-statements:11:9:11:38::More than one statement on a single line:HIGH
+multiple-statements:15:9:15:13::More than one statement on a single line:HIGH
+multiple-statements:19:9:19:12::More than one statement on a single line:HIGH
+multiple-statements:30:26:30:31:MyError:More than one statement on a single line:HIGH