Implement R0205 (#91)

resources/test/src/R0205.py

@@ -0,0 +1,22 @@
+class A:
+    ...
+
+
+class B(object):
+    ...
+
+
+class C(B, object):
+    ...
+
+
+def f():
+    class D(object):
+        ...
+
+
+object = A
+
+
+class E(object):
+    ...

resources/test/src/pyproject.toml

@@ -14,4 +14,5 @@ select = [
     "F831",
     "F841",
     "F901",
+    "R0205",
 ]

src/check_ast.rs

@@ -108,11 +108,37 @@ impl Visitor for Checker<'_> {
                 }
             }
             StmtKind::ClassDef {
+                name,
                 bases,
                 keywords,
                 decorator_list,
                 ..
             } => {
+                if self.settings.select.contains(&CheckCode::R0205) {
+                    for expr in bases {
+                        if let ExprKind::Name { id, .. } = &expr.node {
+                            if id == "object" {
+                                let scope = self.scopes.last().expect("No current scope found.");
+                                match scope.values.get(id) {
+                                    None
+                                    | Some(Binding {
+                                        kind: BindingKind::Builtin,
+                                        ..
+                                    }) => {
+                                        self.checks.push(Check {
+                                            kind: CheckKind::UselessObjectInheritance(
+                                                name.to_string(),
+                                            ),
+                                            location: stmt.location,
+                                        });
+                                    }
+                                    _ => {}
+                                }
+                            }
+                        }
+                    }
+                }
+
                 for expr in bases {
                     self.visit_expr(expr, Some(stmt))
                 }

src/checks.rs

@@ -20,6 +20,7 @@ pub enum CheckCode {
     F831,
     F841,
     F901,
+    R0205,
 }
 
 impl FromStr for CheckCode {
@@ -39,6 +40,7 @@ impl FromStr for CheckCode {
             "F831" => Ok(CheckCode::F831),
             "F841" => Ok(CheckCode::F841),
             "F901" => Ok(CheckCode::F901),
+            "R0205" => Ok(CheckCode::R0205),
             _ => Err(anyhow::anyhow!("Unknown check code: {s}")),
         }
     }
@@ -59,6 +61,7 @@ impl CheckCode {
             CheckCode::F831 => "F831",
             CheckCode::F841 => "F841",
             CheckCode::F901 => "F901",
+            CheckCode::R0205 => "R0205",
         }
     }
 
@@ -77,6 +80,7 @@ impl CheckCode {
             CheckCode::F831 => &LintSource::AST,
             CheckCode::F841 => &LintSource::AST,
             CheckCode::F901 => &LintSource::AST,
+            CheckCode::R0205 => &LintSource::AST,
         }
     }
 }
@@ -100,6 +104,7 @@ pub enum CheckKind {
     UndefinedName(String),
     UnusedImport(String),
     UnusedVariable(String),
+    UselessObjectInheritance(String),
     YieldOutsideFunction,
 }
 
@@ -118,6 +123,7 @@ impl CheckKind {
             CheckKind::UndefinedName(_) => &CheckCode::F821,
             CheckKind::UnusedImport(_) => &CheckCode::F401,
             CheckKind::UnusedVariable(_) => &CheckCode::F841,
+            CheckKind::UselessObjectInheritance(_) => &CheckCode::R0205,
             CheckKind::YieldOutsideFunction => &CheckCode::F704,
         }
     }
@@ -150,6 +156,9 @@ impl CheckKind {
             CheckKind::UnusedVariable(name) => {
                 format!("Local variable `{name}` is assigned to but never used")
             }
+            CheckKind::UselessObjectInheritance(name) => {
+                format!("Class {name} inherits from object")
+            }
             CheckKind::YieldOutsideFunction => {
                 "a `yield` or `yield from` statement outside of a function/method".to_string()
             }

src/linter.rs

@@ -451,4 +451,40 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn r0205() -> Result<()> {
+        let actual = check_path(
+            Path::new("./resources/test/src/R0205.py"),
+            &settings::Settings {
+                line_length: 88,
+                exclude: vec![],
+                select: BTreeSet::from([CheckCode::R0205]),
+            },
+            &cache::Mode::None,
+        )?;
+        let expected = vec![
+            Message {
+                kind: CheckKind::UselessObjectInheritance("B".to_string()),
+                location: Location::new(5, 1),
+                filename: "./resources/test/src/R0205.py".to_string(),
+            },
+            Message {
+                kind: CheckKind::UselessObjectInheritance("C".to_string()),
+                location: Location::new(9, 1),
+                filename: "./resources/test/src/R0205.py".to_string(),
+            },
+            Message {
+                kind: CheckKind::UselessObjectInheritance("D".to_string()),
+                location: Location::new(14, 5),
+                filename: "./resources/test/src/R0205.py".to_string(),
+            },
+        ];
+        assert_eq!(actual.len(), expected.len());
+        for i in 0..actual.len() {
+            assert_eq!(actual[i], expected[i]);
+        }
+
+        Ok(())
+    }
 }

src/pyproject.rs

@@ -249,6 +249,7 @@ other-attribute = 1
                     CheckCode::F831,
                     CheckCode::F841,
                     CheckCode::F901,
+                    CheckCode::R0205,
                 ])),
             }
         );