Generate: add CJK support to TextStreamer (#22664)

src/transformers/generation/streamers.py

@@ -101,6 +101,10 @@ class TextStreamer(BaseStreamer):
             printable_text = text[self.print_len :]
             self.token_cache = []
             self.print_len = 0
+        # If the last token is a CJK character, we print the characters.
+        elif len(text) > 0 and self._is_chinese_char(ord(text[-1])):
+            printable_text = text[self.print_len :]
+            self.print_len += len(printable_text)
         # Otherwise, prints until the last space char (simple heuristic to avoid printing incomplete words,
         # which may change with the subsequent token -- there are probably smarter ways to do this!)
         else:
@@ -127,6 +131,30 @@ class TextStreamer(BaseStreamer):
         """Prints the new text to stdout. If the stream is ending, also prints a newline."""
         print(text, flush=True, end="" if not stream_end else None)
 
+    def _is_chinese_char(self, cp):
+        """Checks whether CP is the codepoint of a CJK character."""
+        # This defines a "chinese character" as anything in the CJK Unicode block:
+        #   https://en.wikipedia.org/wiki/CJK_Unified_Ideographs_(Unicode_block)
+        #
+        # Note that the CJK Unicode block is NOT all Japanese and Korean characters,
+        # despite its name. The modern Korean Hangul alphabet is a different block,
+        # as is Japanese Hiragana and Katakana. Those alphabets are used to write
+        # space-separated words, so they are not treated specially and handled
+        # like the all of the other languages.
+        if (
+            (cp >= 0x4E00 and cp <= 0x9FFF)
+            or (cp >= 0x3400 and cp <= 0x4DBF)  #
+            or (cp >= 0x20000 and cp <= 0x2A6DF)  #
+            or (cp >= 0x2A700 and cp <= 0x2B73F)  #
+            or (cp >= 0x2B740 and cp <= 0x2B81F)  #
+            or (cp >= 0x2B820 and cp <= 0x2CEAF)  #
+            or (cp >= 0xF900 and cp <= 0xFAFF)
+            or (cp >= 0x2F800 and cp <= 0x2FA1F)  #
+        ):  #
+            return True
+
+        return False
+
 
 class TextIteratorStreamer(TextStreamer):
     """