Close #12171: IncrementalEncoder.reset() of CJK codecs (multibytecodec) calls

encreset() instead of decreset().

Doc/library/codecs.rst

@@ -458,7 +458,8 @@ define in order to be compatible with the Python codec registry.
 
    .. method:: reset()
 
-      Reset the encoder to the initial state.
+      Reset the encoder to the initial state. The output is discarded: call
+      ``.encode('', final=True)`` to reset the encoder and to get the output.
 
 
 .. method:: IncrementalEncoder.getstate()

Lib/test/test_multibytecodec.py

@@ -260,7 +260,8 @@ class TestStateful(unittest.TestCase):
     text = '\u4E16\u4E16'
     encoding = 'iso-2022-jp'
     expected = b'\x1b$B@$@$'
-    expected_reset = b'\x1b$B@$@$\x1b(B'
+    reset = b'\x1b(B'
+    expected_reset = expected + reset
 
     def test_encode(self):
         self.assertEqual(self.text.encode(self.encoding), self.expected_reset)
@@ -271,6 +272,8 @@ class TestStateful(unittest.TestCase):
             encoder.encode(char)
             for char in self.text)
         self.assertEqual(output, self.expected)
+        self.assertEqual(encoder.encode('', final=True), self.reset)
+        self.assertEqual(encoder.encode('', final=True), b'')
 
     def test_incrementalencoder_final(self):
         encoder = codecs.getincrementalencoder(self.encoding)()
@@ -279,12 +282,14 @@ class TestStateful(unittest.TestCase):
             encoder.encode(char, index == last_index)
             for index, char in enumerate(self.text))
         self.assertEqual(output, self.expected_reset)
+        self.assertEqual(encoder.encode('', final=True), b'')
 
 class TestHZStateful(TestStateful):
     text = '\u804a\u804a'
     encoding = 'hz'
     expected = b'~{ADAD'
-    expected_reset = b'~{ADAD~}'
+    reset = b'~}'
+    expected_reset = expected + reset
 
 def test_main():
     support.run_unittest(__name__)

Misc/NEWS

@@ -177,6 +177,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #12171: IncrementalEncoder.reset() of CJK codecs (multibytecodec) calls
+  encreset() instead of decreset().
+
 - Issue #12218: Removed wsgiref.egg-info.
 
 - Issue #12196: Add pipe2() to the os module.

Modules/cjkcodecs/multibytecodec.c

@@ -901,11 +901,17 @@ mbiencoder_encode(MultibyteIncrementalEncoderObject *self,
 static PyObject *
 mbiencoder_reset(MultibyteIncrementalEncoderObject *self)
 {
-    if (self->codec->decreset != NULL &&
-        self->codec->decreset(&self->state, self->codec->config) != 0)
-        return NULL;
+    /* Longest output: 4 bytes (b'\x0F\x1F(B') with ISO 2022 */
+    unsigned char buffer[4], *outbuf;
+    Py_ssize_t r;
+    if (self->codec->encreset != NULL) {
+        outbuf = buffer;
+        r = self->codec->encreset(&self->state, self->codec->config,
+                                  &outbuf, sizeof(buffer));
+        if (r != 0)
+            return NULL;
+    }
     self->pendingsize = 0;
-
     Py_RETURN_NONE;
 }