refactor: simplify bound method representation (#12492)

Co-authored-by: Sviatoslav Sydorenko <[email protected]>
Co-authored-by: Farbod Ahmadian <[email protected]>

Author: 3 people

AUTHORS

@@ -149,6 +149,7 @@ Evgeny Seliverstov
 Fabian Sturm
 Fabien Zarifian
 Fabio Zadrozny
+Farbod Ahmadian
 faph
 Felix Hofstätter
 Felix Nieuwenhuizen

changelog/389.improvement.rst

@@ -0,0 +1,38 @@
+The readability of assertion introspection of bound methods has been enhanced
+-- by :user:`farbodahm`, :user:`webknjaz`, :user:`obestwalter`, :user:`flub`
+and :user:`glyphack`.
+
+Earlier, it was like:
+
+.. code-block:: console
+
+    =================================== FAILURES ===================================
+    _____________________________________ test _____________________________________
+
+        def test():
+    >       assert Help().fun() == 2
+    E       assert 1 == 2
+    E        +  where 1 = <bound method Help.fun of <example.Help instance at 0x256a830>>()
+    E        +    where <bound method Help.fun of <example.Help instance at 0x256a830>> = <example.Help instance at 0x256a830>.fun
+    E        +      where <example.Help instance at 0x256a830> = Help()
+
+    example.py:7: AssertionError
+    =========================== 1 failed in 0.03 seconds ===========================
+
+
+And now it's like:
+
+.. code-block:: console
+
+    =================================== FAILURES ===================================
+    _____________________________________ test _____________________________________
+
+        def test():
+    >       assert Help().fun() == 2
+    E       assert 1 == 2
+    E        +  where 1 = fun()
+    E        +    where fun = <test_local.Help object at 0x1074be230>.fun
+    E        +      where <test_local.Help object at 0x1074be230> = Help()
+
+    test_local.py:13: AssertionError
+    =========================== 1 failed in 0.03 seconds ===========================

src/_pytest/_io/saferepr.py

@@ -60,7 +60,6 @@ def repr(self, x: object) -> str:
                 s = ascii(x)
             else:
                 s = super().repr(x)
-
         except (KeyboardInterrupt, SystemExit):
             raise
         except BaseException as exc:

src/_pytest/assertion/rewrite.py

@@ -417,6 +417,10 @@ def _saferepr(obj: object) -> str:
     sequences, especially '\n{' and '\n}' are likely to be present in
     JSON reprs.
     """
+    if isinstance(obj, types.MethodType):
+        # for bound methods, skip redundant <bound method ...> information
+        return obj.__name__
+
     maxsize = _get_maxsize_for_saferepr(util._config)
     return saferepr(obj, maxsize=maxsize).replace("\n", "\\n")
 

testing/test_assertrewrite.py

@@ -10,6 +10,7 @@
 import os
 from pathlib import Path
 import py_compile
+import re
 import stat
 import sys
 import textwrap
@@ -24,6 +25,7 @@
 from _pytest.assertion import util
 from _pytest.assertion.rewrite import _get_assertion_exprs
 from _pytest.assertion.rewrite import _get_maxsize_for_saferepr
+from _pytest.assertion.rewrite import _saferepr
 from _pytest.assertion.rewrite import AssertionRewritingHook
 from _pytest.assertion.rewrite import get_cache_dir
 from _pytest.assertion.rewrite import PYC_TAIL
@@ -2036,7 +2038,9 @@ def test_foo():
         assert test_foo_pyc.is_file()
 
         # normal file: not touched by pytest, normal cache tag
-        bar_init_pyc = get_cache_dir(bar_init) / f"__init__.{sys.implementation.cache_tag}.pyc"
+        bar_init_pyc = (
+            get_cache_dir(bar_init) / f"__init__.{sys.implementation.cache_tag}.pyc"
+        )
         assert bar_init_pyc.is_file()
 
 
@@ -2103,3 +2107,26 @@ def test_foo():
         )
         result = pytester.runpytest()
         assert result.ret == 0
+
+
+class TestSafereprUnbounded:
+    class Help:
+        def bound_method(self):  # pragma: no cover
+            pass
+
+    def test_saferepr_bound_method(self):
+        """saferepr() of a bound method should show only the method name"""
+        assert _saferepr(self.Help().bound_method) == "bound_method"
+
+    def test_saferepr_unbounded(self):
+        """saferepr() of an unbound method should still show the full information"""
+        obj = self.Help()
+        # using id() to fetch memory address fails on different platforms
+        pattern = re.compile(
+            rf"<{Path(__file__).stem}.{self.__class__.__name__}.Help object at 0x[0-9a-fA-F]*>",
+        )
+        assert pattern.match(_saferepr(obj))
+        assert (
+            _saferepr(self.Help)
+            == f"<class '{Path(__file__).stem}.{self.__class__.__name__}.Help'>"
+        )