gh-124927: Fix conversion issue between coordinates and position in REPL (#125001)

Lib/_pyrepl/reader.py

@@ -62,7 +62,7 @@ def disp_str(buffer: str) -> tuple[str, list[int]]:
         elif unicodedata.category(c).startswith("C"):
             c = r"\u%04x" % ord(c)
             s.append(c)
-            b.extend([0] * (len(c) - 1))
+            b.append(len(c))
         else:
             s.append(c)
             b.append(str_width(c))
@@ -577,6 +577,7 @@ class Reader:
         cur_x = self.screeninfo[i][0]
         while cur_x < x:
             if self.screeninfo[i][1][j] == 0:
+                j += 1  # prevent potential future infinite loop
                 continue
             cur_x += self.screeninfo[i][1][j]
             j += 1

Lib/test/test_pyrepl/test_reader.py

@@ -319,3 +319,11 @@ class TestReader(TestCase):
         # Simulate a resize to 0 columns
         reader.screeninfo = []
         self.assertEqual(reader.pos2xy(), (0, 0))
+
+    def test_setpos_from_xy_for_non_printing_char(self):
+        code = "# non \u200c printing character"
+        events = code_to_events(code)
+
+        reader, _ = handle_all_events(events)
+        reader.setpos_from_xy(8, 0)
+        self.assertEqual(reader.pos, 7)

Misc/ACKS

@@ -279,6 +279,7 @@ Laurent De Buyst
 Zach Byrne
 Vedran Čačić
 Nicolas Cadou
+Zhikai Cai
 Jp Calderone
 Ben Caller
 Arnaud Calmettes

Misc/NEWS.d/next/Library/2024-10-05-13-25-07.gh-issue-124927.uzNA32.rst

@@ -0,0 +1 @@
+Non-printing characters are now properly handled in the new REPL.