Issue #28774: Fix start/end pos in unicode_encode_ucs1().

Fix error position of the unicode error in ASCII and Latin1
encoders when a string returned by the error handler contains multiple
non-encodable characters (non-ASCII for the ASCII codec, characters out
of the U+0000-U+00FF range for Latin1).

2 files changed, 7 insertions, 2 deletions

diff --git a/Misc/NEWS b/Misc/NEWS
index 92fca57..af42d90 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,11 @@ What's New in Python 3.7.0 alpha 1
 Core and Builtins
 -----------------
 
+- Issue #28774: Fix error position of the unicode error in ASCII and Latin1
+  encoders when a string returned by the error handler contains multiple
+  non-encodable characters (non-ASCII for the ASCII codec, characters out
+  of the U+0000-U+00FF range for Latin1).
+
 - Issue #28731: Optimize _PyDict_NewPresized() to create correct size dict.
   Improve speed of dict literal with constant keys up to 30%.
 
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index e88a126..2bf48b7 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -6798,7 +6798,7 @@ unicode_encode_ucs1(PyObject *unicode,
                     goto onError;
 
                 /* subtract preallocated bytes */
-                writer.min_size -= 1;
+                writer.min_size -= newpos - collstart;
 
                 if (PyBytes_Check(rep)) {
                     /* Directly copy bytes result to output. */
@@ -6835,7 +6835,7 @@ unicode_encode_ucs1(PyObject *unicode,
                             ch = PyUnicode_READ_CHAR(rep, i);
                             if (ch >= limit) {
                                 raise_encode_exception(&exc, encoding, unicode,
-                                                       pos, pos+1, reason);
+                                                       collstart, collend, reason);
                                 goto onError;
                             }
                             *str = (char)ch;