RustPython · youknowone · Aug 12, 2021 · Aug 12, 2021 · Aug 12, 2021
diff --git a/extra_tests/snippets/bytes.py b/extra_tests/snippets/bytes.py
@@ -633,7 +633,8 @@ def __bytes__(self):
 assert id(a) == id(a)
 assert id(a) != id(a * -1)
 assert id(a) != id(a * 0)
-assert id(a) == id(a * 1)  # only case when `id` stays the same
+assert id(a) == id(a * 1)  # only cases
+assert id(a) == id(1 * a)  # when `id` stays the same
 assert id(a) != id(a * 2)



diff --git a/extra_tests/snippets/strings.py b/extra_tests/snippets/strings.py
@@ -632,7 +632,7 @@ def test_removeprefix():
    assert s_uc.removeprefix('😱') == s_ref_uc[1:]
    assert s_uc.removeprefix('😱fo') == s_ref_uc[3:]
    assert s_uc.removeprefix('😱foo') == s_ref_uc[4:]
-    
+
    assert s_uc.removeprefix('🖖') == s_ref_uc
    assert s_uc.removeprefix('foo') == s_ref_uc
    assert s_uc.removeprefix(' ') == s_ref_uc
@@ -676,7 +676,7 @@ def test_removesuffix():
    assert s_uc.removesuffix('🖖') == s_ref_uc[:-1]
    assert s_uc.removesuffix('oo🖖') == s_ref_uc[:-3]
    assert s_uc.removesuffix('foo🖖') == s_ref_uc[:-4]
-    
+
    assert s_uc.removesuffix('😱') == s_ref_uc
    assert s_uc.removesuffix('foo') == s_ref_uc
    assert s_uc.removesuffix(' ') == s_ref_uc
@@ -702,3 +702,28 @@ def test_removesuffix_types():
 skip_if_unsupported(3,9,test_removeprefix_types)
 skip_if_unsupported(3,9,test_removesuffix)
 skip_if_unsupported(3,9,test_removesuffix_types)
+
+
+# Regression to
+# https://github.com/RustPython/RustPython/issues/2840
+
+a = 'abc123()'
+
+assert id(a) == id(a)
+assert id(a) != id(a * -1)
+assert id(a) != id(a * 0)
+assert id(a) == id(a * 1)  # only cases
+assert id(a) == id(1 * a)  # when `id` stays the same
+assert id(a) != id(a * 2)
+
+
+class MyString(str):
+    pass
+
+b = MyString('0123abc*&')
+assert id(b) == id(b)
+assert id(b) != id(b * -1)
+assert id(b) != id(b * 0)
+assert id(b) != id(b * 1)
+assert id(b) != id(1 * b)
+assert id(b) != id(b * 2)
diff --git a/vm/src/builtins/pystr.rs b/vm/src/builtins/pystr.rs
@@ -329,8 +329,15 @@ impl PyStr {

    #[pymethod(name = "__rmul__")]
    #[pymethod(magic)]
-    fn mul(&self, value: isize) -> String {
-        self.value.repeat(value.to_usize().unwrap_or(0))
+    fn mul(zelf: PyRef<Self>, value: isize, vm: &VirtualMachine) -> PyRef<Self> {
+        if value == 1 && zelf.class().is(&vm.ctx.types.str_type) {
+            // Special case: when some `str` is multiplied by `1`,
+            // nothing really happens, we need to return an object itself
+            // with the same `id()` to be compatible with CPython.
+            // This only works for `str` itself, not its subclasses.
+            return zelf;
+        }
+        Self::from(zelf.value.repeat(value.to_usize().unwrap_or(0))).into_ref(vm)
    }

    #[pymethod(magic)]