[raise-missing-from] Clearer message and example in the documentation (#6576)

* [raise-missing-from] Clearer message and example in the documentation

Co-authored-by: cool-RR <[email protected]>
Co-authored-by: Daniël van Noord <[email protected]>

Refs #5953
Closes #3707

Author: Pierre-Sassoulas

doc/data/messages/r/raise-missing-from/bad.py

@@ -0,0 +1,4 @@
+try:
+    1 / 0
+except ZeroDivisionError as e:
+    raise ValueError("Rectangle Area cannot be zero")  # [raise-missing-from]

doc/data/messages/r/raise-missing-from/good.py

@@ -0,0 +1,4 @@
+try:
+    1 / 0
+except ZeroDivisionError as e:
+    raise ValueError("Rectangle Area cannot be zero") from e

doc/data/messages/r/raise-missing-from/related.rst

@@ -0,0 +1 @@
+- `PEP 3132 <https://peps.python.org/pep-3132/>`_

pylint/checkers/exceptions.py

@@ -15,6 +15,7 @@
 
 from pylint import checkers
 from pylint.checkers import utils
+from pylint.interfaces import HIGH
 from pylint.typing import MessageDefinitionTuple
 
 if TYPE_CHECKING:
@@ -131,13 +132,13 @@ def _is_raising(body: list) -> bool:
         "try-except-raise block!",
     ),
     "W0707": (
-        "Consider explicitly re-raising using the 'from' keyword",
+        "Consider explicitly re-raising using %s'%s from %s'",
         "raise-missing-from",
-        "Python 3's exception chaining means it shows the traceback of the "
-        "current exception, but also the original exception. Not using `raise "
-        "from` makes the traceback inaccurate, because the message implies "
-        "there is a bug in the exception-handling code itself, which is a "
-        "separate situation than wrapping an exception.",
+        "Python's exception chaining shows the traceback of the current exception, "
+        "but also of the original exception. When you raise a new exception after "
+        "another exception was caught it's likely that the second exception is a "
+        "friendly re-wrapping of the first exception. In such cases `raise from` "
+        "provides a better link between the two tracebacks in the final error.",
     ),
     "W0711": (
         'Exception to catch is the result of a binary "%s" operation',
@@ -334,16 +335,33 @@ def _check_raise_missing_from(self, node: nodes.Raise) -> None:
         if containing_except_node.name is None:
             # The `except` doesn't have an `as exception:` part, meaning there's no way that
             # the `raise` is raising the same exception.
-            self.add_message("raise-missing-from", node=node)
-        elif isinstance(node.exc, nodes.Call) and isinstance(node.exc.func, nodes.Name):
-            # We have a `raise SomeException(whatever)`.
-            self.add_message("raise-missing-from", node=node)
+            class_of_old_error = "Exception"
+            if isinstance(containing_except_node.type, (nodes.Name, nodes.Tuple)):
+                # 'except ZeroDivisionError' or 'except (ZeroDivisionError, ValueError)'
+                class_of_old_error = containing_except_node.type.as_string()
+            self.add_message(
+                "raise-missing-from",
+                node=node,
+                args=(
+                    f"'except {class_of_old_error} as exc' and ",
+                    node.as_string(),
+                    "exc",
+                ),
+                confidence=HIGH,
+            )
         elif (
-            isinstance(node.exc, nodes.Name)
+            isinstance(node.exc, nodes.Call)
+            and isinstance(node.exc.func, nodes.Name)
+            or isinstance(node.exc, nodes.Name)
             and node.exc.name != containing_except_node.name.name
         ):
-            # We have a `raise SomeException`.
-            self.add_message("raise-missing-from", node=node)
+            # We have a `raise SomeException(whatever)` or a `raise SomeException`
+            self.add_message(
+                "raise-missing-from",
+                node=node,
+                args=("", node.as_string(), containing_except_node.name.name),
+                confidence=HIGH,
+            )
 
     def _check_catching_non_exception(self, handler, exc, part):
         if isinstance(exc, nodes.Tuple):

tests/functional/r/raise_missing_from.py

@@ -1,8 +1,10 @@
 # pylint:disable=missing-docstring, unreachable, using-constant-test, invalid-name, bare-except
 # pylint:disable=try-except-raise, undefined-variable, too-few-public-methods, superfluous-parens
 
-################################################################################
-# Positives:
+try:
+    1 / 0
+except:
+    raise ValueError('Invalid integer')  # [raise-missing-from]
 
 try:
     1 / 0
@@ -13,9 +15,8 @@
 try:
     1 / 0
 except ZeroDivisionError:
-    # Our algorithm doesn't have to be careful about the complicated expression below, because
-    # the exception above wasn't bound to a name.
-    # +1: [raise-missing-from]
+    # Our algorithm doesn't have to be careful about the complicated expression below,
+    # because the exception above wasn't bound to a name. # +1: [raise-missing-from]
     raise (foo + bar).baz
 
 try:
@@ -59,8 +60,26 @@
     raise KeyError(whatever, whatever=whatever)
 
 
-################################################################################
-# Negatives (Same cases as above, except with `from`):
+try:
+    1 / 0
+except (ZeroDivisionError, ValueError, KeyError):
+    if 1:
+        if 2:
+            pass
+        else:
+            with whatever:
+                # +1: [raise-missing-from]
+                raise KeyError(whatever, whatever=whatever)
+    else:
+        # +1: [raise-missing-from]
+        raise KeyError(whatever, overever=12)
+
+try:
+    # Taken from https://github.com/python/cpython/blob/3.10/Lib/plistlib.py#L459
+    pass
+except (OSError, IndexError, struct.error, OverflowError,
+        ValueError):
+    raise InvalidFileException()  # [raise-missing-from]
 
 try:
     1 / 0
@@ -107,10 +126,6 @@
 except ZeroDivisionError as e:
     raise KeyError(whatever, whatever=whatever) from foo
 
-
-################################################################################
-# Other negatives:
-
 try:
     1 / 0
 except ZeroDivisionError:

tests/functional/r/raise_missing_from.txt

@@ -1,7 +1,11 @@
-raise-missing-from:11:4:11:18::Consider explicitly re-raising using the 'from' keyword:UNDEFINED
-raise-missing-from:19:4:19:25::Consider explicitly re-raising using the 'from' keyword:UNDEFINED
-raise-missing-from:25:4:25:18::Consider explicitly re-raising using the 'from' keyword:UNDEFINED
-raise-missing-from:31:4:31:18::Consider explicitly re-raising using the 'from' keyword:UNDEFINED
-raise-missing-from:45:20:45:34::Consider explicitly re-raising using the 'from' keyword:UNDEFINED
-raise-missing-from:53:4:53:20::Consider explicitly re-raising using the 'from' keyword:UNDEFINED
-raise-missing-from:59:4:59:47::Consider explicitly re-raising using the 'from' keyword:UNDEFINED
+raise-missing-from:7:4:7:39::Consider explicitly re-raising using 'except Exception as exc' and 'raise ValueError('Invalid integer') from exc':HIGH
+raise-missing-from:13:4:13:18::Consider explicitly re-raising using 'except ZeroDivisionError as exc' and 'raise KeyError from exc':HIGH
+raise-missing-from:20:4:20:25::Consider explicitly re-raising using 'except ZeroDivisionError as exc' and 'raise (foo + bar).baz from exc':HIGH
+raise-missing-from:26:4:26:18::Consider explicitly re-raising using 'raise KeyError from e':HIGH
+raise-missing-from:32:4:32:18::Consider explicitly re-raising using 'raise KeyError from e':HIGH
+raise-missing-from:46:20:46:34::Consider explicitly re-raising using 'raise KeyError from e':HIGH
+raise-missing-from:54:4:54:20::Consider explicitly re-raising using 'raise KeyError() from e':HIGH
+raise-missing-from:60:4:60:47::Consider explicitly re-raising using 'raise KeyError(whatever, whatever=whatever) from e':HIGH
+raise-missing-from:72:16:72:59::Consider explicitly re-raising using 'except (ZeroDivisionError, ValueError, KeyError) as exc' and 'raise KeyError(whatever, whatever=whatever) from exc':HIGH
+raise-missing-from:75:8:75:45::Consider explicitly re-raising using 'except (ZeroDivisionError, ValueError, KeyError) as exc' and 'raise KeyError(whatever, overever=12) from exc':HIGH
+raise-missing-from:82:4:82:32::Consider explicitly re-raising using 'except (OSError, IndexError, struct.error, OverflowError, ValueError) as exc' and 'raise InvalidFileException() from exc':HIGH