enhance excinfo.match failure output

* now multiline and compares regexes
* warns on forgotten escaping

Author: RonnyPfannschmidt

src/_pytest/_code/code.py

@@ -662,10 +662,11 @@ def match(self, regexp: Union[str, Pattern[str]]) -> "Literal[True]":
         If it matches `True` is returned, otherwise an `AssertionError` is raised.
         """
         __tracebackhide__ = True
-        msg = "Regex pattern {!r} does not match {!r}."
-        if regexp == str(self.value):
-            msg += " Did you mean to `re.escape()` the regex?"
-        assert re.search(regexp, str(self.value)), msg.format(regexp, str(self.value))
+        value = str(self.value)
+        msg = f"Regex pattern did not match.\n Regex: {regexp!r}\n Input: {value!r}"
+        if regexp == value:
+            msg += "\n Did you mean to `re.escape()` the regex?"
+        assert re.search(regexp, value), msg
         # Return True to allow for "assert excinfo.match()".
         return True
 

testing/code/test_excinfo.py

@@ -420,18 +420,20 @@ def test_division_zero():
             excinfo.match(r'[123]+')
     """
     )
-    result = pytester.runpytest()
+    result = pytester.runpytest("--tb=short")
     assert result.ret != 0
 
-    exc_msg = "Regex pattern '[[]123[]]+' does not match 'division by zero'."
-    result.stdout.fnmatch_lines([f"E * AssertionError: {exc_msg}"])
+    match = [
+        r"E .* AssertionError: Regex pattern did not match.",
+        r"E .* Regex: '\[123\]\+'",
+        r"E .* Input: 'division by zero'",
+    ]
+    result.stdout.re_match_lines(match)
     result.stdout.no_fnmatch_line("*__tracebackhide__ = True*")
 
     result = pytester.runpytest("--fulltrace")
     assert result.ret != 0
-    result.stdout.fnmatch_lines(
-        ["*__tracebackhide__ = True*", f"E * AssertionError: {exc_msg}"]
-    )
+    result.stdout.re_match_lines([r".*__tracebackhide__ = True.*", *match])
 
 
 class TestFormattedExcinfo:

testing/python/raises.py

@@ -191,10 +191,12 @@ def test_raises_match(self) -> None:
             int("asdf")
 
         msg = "with base 16"
-        expr = "Regex pattern {!r} does not match \"invalid literal for int() with base 10: 'asdf'\".".format(
-            msg
+        expr = (
+            "Regex pattern did not match.\n"
+            f" Regex: {msg!r}\n"
+            " Input: \"invalid literal for int() with base 10: 'asdf'\""
         )
-        with pytest.raises(AssertionError, match=re.escape(expr)):
+        with pytest.raises(AssertionError, match="(?m)" + re.escape(expr)):
             with pytest.raises(ValueError, match=msg):
                 int("asdf", base=10)
 
@@ -217,7 +219,7 @@ def test_match_failure_string_quoting(self):
             with pytest.raises(AssertionError, match="'foo"):
                 raise AssertionError("'bar")
         (msg,) = excinfo.value.args
-        assert msg == 'Regex pattern "\'foo" does not match "\'bar".'
+        assert msg == '''Regex pattern did not match.\n Regex: "'foo"\n Input: "'bar"'''
 
     def test_match_failure_exact_string_message(self):
         message = "Oh here is a message with (42) numbers in parameters"
@@ -226,9 +228,10 @@ def test_match_failure_exact_string_message(self):
                 raise AssertionError(message)
         (msg,) = excinfo.value.args
         assert msg == (
-            "Regex pattern 'Oh here is a message with (42) numbers in "
-            "parameters' does not match 'Oh here is a message with (42) "
-            "numbers in parameters'. Did you mean to `re.escape()` the regex?"
+            "Regex pattern did not match.\n"
+            " Regex: 'Oh here is a message with (42) numbers in parameters'\n"
+            " Input: 'Oh here is a message with (42) numbers in parameters'\n"
+            " Did you mean to `re.escape()` the regex?"
         )
 
     def test_raises_match_wrong_type(self):