assert: _diff_text: use repr() with line endings

Author: blueyed

src/_pytest/assertion/util.py

@@ -246,8 +246,8 @@ def _diff_text(left: str, right: str, verbose: int = 0) -> List[str]:
         wcwidth(ch) <= 0
         for ch in [ch for lines in left_lines + right_lines for ch in lines]
     ):
-        left_lines = [repr(x) for x in left_lines]
-        right_lines = [repr(x) for x in right_lines]
+        left_lines = [repr(x) for x in left.splitlines(True)]
+        right_lines = [repr(x) for x in right.splitlines(True)]
         explanation += [
             "NOTE: Strings contain non-printable characters. Escaping them using repr()."
         ]

testing/test_assertion.py

@@ -1519,11 +1519,13 @@ def test_diff_different_line_endings():
         r"  line2",
     ]
 
-    # Only '\r' is considered non-printable
+    # Only '\r' is considered non-printable, repr() is used on original lines.
     assert callequal("line1\r\nline2", "line1\nline2\r", verbose=2) == [
         r"'line1\r\nline2' == 'line1\nline2\r'",
         r"NOTE: Strings contain non-printable characters. Escaping them using repr().",
-        r"  'line1'",
+        r"- 'line1\n'",
+        r"+ 'line1\r\n'",
+        r"?        ++",
         r"- 'line2\r'",
         r"?       --",
         r"+ 'line2'",