raises: suppress exception cause in raises match failures (#14391)

(cherry picked from commit cd7592c)

Author: lavaFreak

AUTHORS

@@ -179,6 +179,7 @@ Fraser Stark
 Freya Bruhin
 Gabriel Landau
 Gabriel Reis
+Garion Milazzo
 Garvit Shubham
 Gene Wood
 George Kussumoto

changelog/14389.bugfix.rst

@@ -0,0 +1 @@
+Improved :func:`pytest.raises(..., match=...) <pytest.raises>` failures to suppress the mismatched exception as a cause of the resulting ``AssertionError``.

src/_pytest/raises.py

@@ -716,7 +716,7 @@ def __exit__(
         if not self.matches(exc_val):
             if self._just_propagate:
                 return False
-            raise AssertionError(self._fail_reason)
+            raise AssertionError(self._fail_reason) from None
 
         # Cast to narrow the exception type now that it's verified....
         # even though the TypeGuard in self.matches should be narrowing

testing/python/raises.py

@@ -177,6 +177,33 @@ def test_invalid_regex():
         result.stdout.no_fnmatch_line("*File*")
         result.stdout.no_fnmatch_line("*line*")
 
+    def test_raises_match_failure_suppresses_exception_context(
+        self, pytester: Pytester
+    ) -> None:
+        pytester.makepyfile(
+            """
+            import pytest
+
+            def test_raises_match_failure():
+                with pytest.raises(ValueError, match="expected"):
+                    raise ValueError("actual")
+            """
+        )
+        result = pytester.runpytest("--tb=short")
+        assert result.ret == 1
+        result.stdout.fnmatch_lines(
+            [
+                "*E*AssertionError: Regex pattern did not match.*",
+            ]
+        )
+        result.stdout.no_fnmatch_line("*ValueError: actual")
+        result.stdout.no_fnmatch_line(
+            "*The above exception was the direct cause of the following exception:*"
+        )
+        result.stdout.no_fnmatch_line(
+            "*During handling of the above exception, another exception occurred:*"
+        )
+
     def test_noclass(self) -> None:
         with pytest.raises(TypeError):
             pytest.raises("wrong", lambda: None)  # type: ignore[call-overload]