From 121b35d27cc6b81899af2c78a93dbf3d8ab05f85 Mon Sep 17 00:00:00 2001
From: Dean Li <deantvv@gmail.com>
Date: Thu, 19 May 2022 23:15:04 +0800
Subject: [PATCH] io: enhance error message in Buffered* class

---
 Lib/test/test_io.py |  6 ------
 vm/src/stdlib/io.rs | 10 +++++++++-
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index b30a35d35..31614b829 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -1593,8 +1593,6 @@ class CBufferedReaderTest(BufferedReaderTest, SizeofTest):
             support.gc_collect()
         self.assertIsNone(wr(), wr)
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_args_error(self):
         # Issue #17275
         with self.assertRaisesRegex(TypeError, "BufferedReader"):
@@ -1974,8 +1972,6 @@ class CBufferedWriterTest(BufferedWriterTest, SizeofTest):
         with self.open(os_helper.TESTFN, "rb") as f:
             self.assertEqual(f.read(), b"123xxx")
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_args_error(self):
         # Issue #17275
         with self.assertRaisesRegex(TypeError, "BufferedWriter"):
@@ -2460,8 +2456,6 @@ class CBufferedRandomTest(BufferedRandomTest, SizeofTest):
         CBufferedReaderTest.test_garbage_collection(self)
         CBufferedWriterTest.test_garbage_collection(self)
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_args_error(self):
         # Issue #17275
         with self.assertRaisesRegex(TypeError, "BufferedRandom"):
diff --git a/vm/src/stdlib/io.rs b/vm/src/stdlib/io.rs
index e7f9ca2dd..4be12ba8d 100644
--- a/vm/src/stdlib/io.rs
+++ b/vm/src/stdlib/io.rs
@@ -1361,6 +1361,7 @@ mod _io {
 
     #[pyimpl]
     trait BufferedMixin: PyPayload {
+        const CLASS_NAME: &'static str;
         const READABLE: bool;
         const WRITABLE: bool;
         const SEEKABLE: bool = false;
@@ -1374,7 +1375,11 @@ mod _io {
         #[pyslot]
         fn slot_init(zelf: PyObjectRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult<()> {
             let zelf: PyRef<Self> = zelf.try_into_value(vm)?;
-            let (raw, BufferSize { buffer_size }): (PyObjectRef, _) = args.bind(vm)?;
+            let (raw, BufferSize { buffer_size }): (PyObjectRef, _) =
+                args.bind(vm).map_err(|e| {
+                    let msg = format!("{}() {}", Self::CLASS_NAME, *e.str(vm));
+                    vm.new_exception_msg(e.class().clone(), msg)
+                })?;
             zelf.init(raw, BufferSize { buffer_size }, vm)
         }
 
@@ -1657,6 +1662,7 @@ mod _io {
         data: PyThreadMutex<BufferedData>,
     }
     impl BufferedMixin for BufferedReader {
+        const CLASS_NAME: &'static str = "BufferedReader";
         const READABLE: bool = true;
         const WRITABLE: bool = false;
         fn data(&self) -> &PyThreadMutex<BufferedData> {
@@ -1706,6 +1712,7 @@ mod _io {
         data: PyThreadMutex<BufferedData>,
     }
     impl BufferedMixin for BufferedWriter {
+        const CLASS_NAME: &'static str = "BufferedWriter";
         const READABLE: bool = false;
         const WRITABLE: bool = true;
         fn data(&self) -> &PyThreadMutex<BufferedData> {
@@ -1734,6 +1741,7 @@ mod _io {
         data: PyThreadMutex<BufferedData>,
     }
     impl BufferedMixin for BufferedRandom {
+        const CLASS_NAME: &'static str = "BufferedRandom";
         const READABLE: bool = true;
         const WRITABLE: bool = true;
         const SEEKABLE: bool = true;