Return ascii(obj) or repr(obj) + tests

src/_pytest/_io/saferepr.py

@@ -41,7 +41,7 @@ class SafeRepr(reprlib.Repr):
     information on exceptions raised during the call.
     """
 
-    def __init__(self, maxsize: Optional[int]) -> None:
+    def __init__(self, maxsize: Optional[int], use_ascii: bool = False) -> None:
         """
         :param maxsize:
             If not None, will truncate the resulting repr to that specific size, using ellipsis
@@ -54,9 +54,13 @@ class SafeRepr(reprlib.Repr):
         # truncation.
         self.maxstring = maxsize if maxsize is not None else 1_000_000_000
         self.maxsize = maxsize
+        self.use_ascii = use_ascii
 
     def repr(self, x: object) -> str:
         try:
+            if self.use_ascii:
+                return ascii(x)
+
             s = super().repr(x)
         except (KeyboardInterrupt, SystemExit):
             raise
@@ -107,10 +111,7 @@ def saferepr(
     stdlib.
     """
 
-    if use_ascii:
-        obj = ascii(obj)
-
-    return SafeRepr(maxsize).repr(obj)
+    return SafeRepr(maxsize, use_ascii).repr(obj)
 
 
 def saferepr_unlimited(obj: object, use_ascii: bool = True) -> str:
@@ -126,7 +127,7 @@ def saferepr_unlimited(obj: object, use_ascii: bool = True) -> str:
     """
     try:
         if use_ascii:
-            obj = ascii(obj)
+            return ascii(obj)
         return repr(obj)
     except Exception as exc:
         return _format_repr_exception(exc, obj)

src/_pytest/assertion/util.py

@@ -163,6 +163,8 @@ def assertrepr_compare(
     """Return specialised explanations for some operators/operands."""
     verbose = config.getoption("verbose")
 
+    # Strings which normalize equal are often hard to distinguish when printed; use ascii() to make this easier.
+    # See issue #3246.
     use_ascii = (
         isinstance(left, str)
         and isinstance(right, str)

testing/test_assertion.py

@@ -782,14 +782,14 @@ class TestAssert_reprcompare:
         right = "hyva\u0308"
         expl = callequal(left, right)
         assert expl == [
-            "\"'hyv\\\\xe4'\" == \"'hyva\\\\u0308'\"",
+            r"'hyv\xe4' == 'hyva\u0308'",
             f"- {str(right)}",
             f"+ {str(left)}",
         ]
 
         expl = callequal(left, right, verbose=2)
         assert expl == [
-            "\"'hyv\\\\xe4'\" == \"'hyva\\\\u0308'\"",
+            r"'hyv\xe4' == 'hyva\u0308'",
             f"- {str(right)}",
             f"+ {str(left)}",
         ]