Properly truncate characters when splitting up strings in error repr

Fixes pydantic/pydantic#6448

Author: adriangb

src/errors/validation_exception.rs

@@ -233,11 +233,13 @@ impl ValidationError {
 macro_rules! truncate_input_value {
     ($out:expr, $value:expr) => {
         if $value.len() > 50 {
+            dbg!($value.floor_char_boundary(25));
+            dbg!($value.ceil_char_boundary($value.len() - 24));
             write!(
                 $out,
                 ", input_value={}...{}",
-                &$value[0..25],
-                &$value[$value.len() - 24..]
+                &$value[0..$value.floor_char_boundary(25)],
+                &$value[$value.ceil_char_boundary($value.len() - 24)..]
             )?;
         } else {
             write!($out, ", input_value={}", $value)?;

src/lib.rs

@@ -1,3 +1,4 @@
+#![feature(round_char_boundary)]
 #![cfg_attr(has_no_coverage, feature(no_coverage))]
 
 extern crate core;

tests/test_misc.py

@@ -1,11 +1,13 @@
 import copy
+import os
 import pickle
 import re
+from unittest.mock import patch
 
 import pytest
 from typing_extensions import get_args
 
-from pydantic_core import CoreSchema, CoreSchemaType, PydanticUndefined
+from pydantic_core import CoreSchema, CoreSchemaType, PydanticUndefined, core_schema
 from pydantic_core._pydantic_core import SchemaError, SchemaValidator, ValidationError, __version__, build_profile
 
 
@@ -177,3 +179,20 @@ def test_undefined():
     assert undefined_deepcopy is PydanticUndefined
 
     assert pickle.loads(pickle.dumps(PydanticUndefined)) is PydanticUndefined
+
+
+def test_unicode_error_input_repr() -> None:
+    """https://github.com/pydantic/pydantic/issues/6448"""
+
+    schema = core_schema.int_schema()
+
+    validator = SchemaValidator(schema)
+
+    danger_str = 'ÿ' * 1000
+    with patch.dict(os.environ, {'PYDANTIC_ERRORS_OMIT_URL': '1'}):
+        with pytest.raises(ValidationError) as exc_info:
+            validator.validate_python(danger_str)
+        assert (
+            repr(exc_info.value)
+            == "1 validation error for int\n  Input should be a valid integer, unable to parse string as an integer [type=int_parsing, input_value='ÿÿÿÿÿÿÿÿÿÿÿÿ...ÿÿÿÿÿÿÿÿÿÿÿ', input_type=str]"  # noqa: E501
+        )