Fix a crash on psycopg2 for elif used (#5369)

* Fix a crash in the ``check_elif`` extensions where an undetected if in a comprehension
  with an if statement within a f-string resulted in an out of range error. The checker no
  longer relies on counting if statements anymore and uses known if statements locations instead.
  It should not crash on badly parsed if statements anymore. specify the confidence of the message

* Remove disable for else-if-used in pylint/checkers/classes.py

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

ChangeLog

@@ -17,6 +17,11 @@ Release date: TBA
 
 * Fix ``install graphiz`` message which isn't needed for puml output format.
 
+* Fix a crash in the ``check_elif`` extensions where an undetected if in a comprehension
+  with an if statement within a f-string resulted in an out of range error. The checker no
+  longer relies on counting if statements anymore and uses known if statements locations instead.
+  It should not crash on badly parsed if statements anymore.
+
 * Fix ``simplify-boolean-expression`` when condition can be inferred as False.
 
   Closes #5200

pylint/checkers/classes.py

@@ -1848,20 +1848,18 @@ def _check_first_arg_for_type(self, node, metaclass=0):
                     "bad-mcs-method-argument",
                     node.name,
                 )
-        # regular class
-        else:  # pylint: disable=else-if-used
-            # class method
-            if node.type == "classmethod" or node.name == "__class_getitem__":
-                self._check_first_arg_config(
-                    first,
-                    self.config.valid_classmethod_first_arg,
-                    node,
-                    "bad-classmethod-argument",
-                    node.name,
-                )
-            # regular method without self as argument
-            elif first != "self":
-                self.add_message("no-self-argument", node=node)
+        # regular class with class method
+        elif node.type == "classmethod" or node.name == "__class_getitem__":
+            self._check_first_arg_config(
+                first,
+                self.config.valid_classmethod_first_arg,
+                node,
+                "bad-classmethod-argument",
+                node.name,
+            )
+        # regular class with regular method without self as argument
+        elif first != "self":
+            self.add_message("no-self-argument", node=node)
 
     def _check_first_arg_config(self, first, config, node, message, method_name):
         if first not in config:

pylint/extensions/check_elif.py

@@ -15,7 +15,7 @@
 
 from pylint.checkers import BaseTokenChecker
 from pylint.checkers.utils import check_messages
-from pylint.interfaces import IAstroidChecker, ITokenChecker
+from pylint.interfaces import HIGH, IAstroidChecker, ITokenChecker
 
 
 class ElseifUsedChecker(BaseTokenChecker):
@@ -38,37 +38,27 @@ def __init__(self, linter=None):
         self._init()
 
     def _init(self):
-        self._elifs = []
-        self._if_counter = 0
+        self._elifs = {}
 
     def process_tokens(self, tokens):
-        # Process tokens and look for 'if' or 'elif'
-        for _, token, _, _, _ in tokens:
-            if token == "elif":
-                self._elifs.append(True)
-            elif token == "if":
-                self._elifs.append(False)
+        """Process tokens and look for 'if' or 'elif'"""
+        self._elifs = {
+            begin: token for _, token, begin, _, _ in tokens if token in {"elif", "if"}
+        }
 
     def leave_module(self, _: nodes.Module) -> None:
         self._init()
 
-    def visit_ifexp(self, node: nodes.IfExp) -> None:
-        if isinstance(node.parent, nodes.FormattedValue):
-            return
-        self._if_counter += 1
-
-    def visit_comprehension(self, node: nodes.Comprehension) -> None:
-        self._if_counter += len(node.ifs)
-
     @check_messages("else-if-used")
     def visit_if(self, node: nodes.If) -> None:
-        if isinstance(node.parent, nodes.If):
-            orelse = node.parent.orelse
-            # current if node must directly follow an "else"
-            if orelse and orelse == [node]:
-                if not self._elifs[self._if_counter]:
-                    self.add_message("else-if-used", node=node)
-        self._if_counter += 1
+        """Current if node must directly follow an 'else'"""
+        if (
+            isinstance(node.parent, nodes.If)
+            and node.parent.orelse == [node]
+            and (node.lineno, node.col_offset) in self._elifs
+            and self._elifs[(node.lineno, node.col_offset)] == "if"
+        ):
+            self.add_message("else-if-used", node=node, confidence=HIGH)
 
 
 def register(linter):

tests/functional/ext/check_elif/check_elif.py

@@ -1,4 +1,7 @@
+# pylint: disable=no-else-raise,unsupported-membership-test,using-constant-test
+
 """Checks use of "else if" triggers a refactor message"""
+from typing import Union, Sequence, Any, Mapping
 
 
 def my_function():
@@ -7,7 +10,7 @@ def my_function():
     if myint > 5:
         pass
     else:
-        if myint <= 5:  #  [else-if-used]
+        if myint <= 5:  # [else-if-used]
             pass
         else:
             myint = 3
@@ -25,3 +28,21 @@ def my_function():
                 if myint:
                     pass
                 myint = 4
+
+
+def _if_in_fstring_comprehension_with_elif(
+    params: Union[Sequence[Any], Mapping[str, Any]]
+):
+    order = {}
+    if "z" not in "false":
+        raise TypeError(
+            f" {', '.join(sorted(i for i in order or () if i not in params))}"
+        )
+    elif "z" not in "true":
+        pass
+    else:
+        if "t" not in "false":  # [else-if-used]
+            raise TypeError("d")
+        else:
+            if "y" in "life":  # [else-if-used]
+                print("e")

tests/functional/ext/check_elif/check_elif.txt

@@ -1,2 +1,4 @@
-else-if-used:10:8:my_function:"Consider using ""elif"" instead of ""else if""":HIGH
-else-if-used:22:20:my_function:"Consider using ""elif"" instead of ""else if""":HIGH
+else-if-used:13:8:my_function:"Consider using ""elif"" instead of ""else if""":HIGH
+else-if-used:25:20:my_function:"Consider using ""elif"" instead of ""else if""":HIGH
+else-if-used:44:8:_if_in_fstring_comprehension_with_elif:"Consider using ""elif"" instead of ""else if""":HIGH
+else-if-used:47:12:_if_in_fstring_comprehension_with_elif:"Consider using ""elif"" instead of ""else if""":HIGH