[pylint] Exclude self and cls when counting method arguments

crates/ruff_linter/resources/test/fixtures/pylint/too_many_positional.py

@@ -1,4 +1,4 @@
-def f(x, y, z, t, u, v, w, r):  # Too many positional arguments (8/3)
+def f(x, y, z, t, u, v, w, r):  # Too many positional arguments (8/5)
     pass
 
 
@@ -18,13 +18,44 @@ def f(x=1, y=1, z=1):  # OK
     pass
 
 
-def f(x, y, z, /, u, v, w):  # Too many positional arguments (6/3)
+def f(x, y, z, /, u, v, w):  # Too many positional arguments (6/5)
     pass
 
 
 def f(x, y, z, *, u, v, w):  # OK
     pass
 
 
-def f(x, y, z, a, b, c, *, u, v, w):  # Too many positional arguments (6/3)
+def f(x, y, z, a, b, c, *, u, v, w):  # Too many positional arguments (6/5)
     pass
+
+
+class C:
+    def f(self, a, b, c, d, e):  # OK
+        pass
+
+    def f(self, /, a, b, c, d, e):  # OK
+        pass
+
+    def f(weird_self_name, a, b, c, d, e):  # OK
+        pass
+
+    def f(self, a, b, c, d, e, g):  # Too many positional arguments (6/5)
+        pass
+
+    @staticmethod
+    def f(self, a, b, c, d, e):  # Too many positional arguments (6/5)
+        pass
+
+    @classmethod
+    def f(cls, a, b, c, d, e):  # OK
+        pass
+
+    def f(*, self, a, b, c, d, e):  # OK
+        pass
+
+    def f(self=1, a=1, b=1, c=1, d=1, e=1):  # OK
+        pass
+
+    def f():  # OK
+        pass

crates/ruff_linter/src/rules/pylint/rules/too_many_positional.rs

@@ -1,7 +1,7 @@
 use ruff_diagnostics::{Diagnostic, Violation};
 use ruff_macros::{derive_message_formats, violation};
 use ruff_python_ast::{self as ast, identifier::Identifier};
-use ruff_python_semantic::analyze::visibility;
+use ruff_python_semantic::analyze::{function_type, visibility};
 
 use crate::checkers::ast::Checker;
 
@@ -57,7 +57,7 @@ impl Violation for TooManyPositional {
 
 /// PLR0917
 pub(crate) fn too_many_positional(checker: &mut Checker, function_def: &ast::StmtFunctionDef) {
-    let num_positional_args = function_def
+    let mut num_positional_args = function_def
         .parameters
         .args
         .iter()
@@ -70,11 +70,30 @@ pub(crate) fn too_many_positional(checker: &mut Checker, function_def: &ast::Stm
         })
         .count();
 
+    let semantic = checker.semantic();
+
+    // Check if the function is a method or class method.
+    if matches!(
+        function_type::classify(
+            &function_def.name,
+            &function_def.decorator_list,
+            semantic.current_scope(),
+            semantic,
+            &checker.settings.pep8_naming.classmethod_decorators,
+            &checker.settings.pep8_naming.staticmethod_decorators,
+        ),
+        function_type::FunctionType::Method | function_type::FunctionType::ClassMethod
+    ) {
+        // If so, we need to subtract one from the number of positional arguments, since the first
+        // argument is always `self` or `cls`.
+        num_positional_args = num_positional_args.saturating_sub(1);
+    }
+
     if num_positional_args > checker.settings.pylint.max_positional_args {
         // Allow excessive arguments in `@override` or `@overload` methods, since they're required
         // to adhere to the parent signature.
-        if visibility::is_override(&function_def.decorator_list, checker.semantic())
-            || visibility::is_overload(&function_def.decorator_list, checker.semantic())
+        if visibility::is_override(&function_def.decorator_list, semantic)
+            || visibility::is_overload(&function_def.decorator_list, semantic)
         {
             return;
         }

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLR0917_too_many_positional.py.snap

@@ -3,23 +3,40 @@ source: crates/ruff_linter/src/rules/pylint/mod.rs
 ---
 too_many_positional.py:1:5: PLR0917 Too many positional arguments (8/5)
   |
-1 | def f(x, y, z, t, u, v, w, r):  # Too many positional arguments (8/3)
+1 | def f(x, y, z, t, u, v, w, r):  # Too many positional arguments (8/5)
   |     ^ PLR0917
 2 |     pass
   |
 
 too_many_positional.py:21:5: PLR0917 Too many positional arguments (6/5)
    |
-21 | def f(x, y, z, /, u, v, w):  # Too many positional arguments (6/3)
+21 | def f(x, y, z, /, u, v, w):  # Too many positional arguments (6/5)
    |     ^ PLR0917
 22 |     pass
    |
 
 too_many_positional.py:29:5: PLR0917 Too many positional arguments (6/5)
    |
-29 | def f(x, y, z, a, b, c, *, u, v, w):  # Too many positional arguments (6/3)
+29 | def f(x, y, z, a, b, c, *, u, v, w):  # Too many positional arguments (6/5)
    |     ^ PLR0917
 30 |     pass
    |
 
+too_many_positional.py:43:9: PLR0917 Too many positional arguments (6/5)
+   |
+41 |         pass
+42 | 
+43 |     def f(self, a, b, c, d, e, g):  # Too many positional arguments (6/5)
+   |         ^ PLR0917
+44 |         pass
+   |
+
+too_many_positional.py:47:9: PLR0917 Too many positional arguments (6/5)
+   |
+46 |     @staticmethod
+47 |     def f(self, a, b, c, d, e):  # Too many positional arguments (6/5)
+   |         ^ PLR0917
+48 |         pass
+   |
+