Improve docs for warnings capture and PEP-0506 remarks

changelog/2908.feature.rst

@@ -1,3 +1,5 @@
 ``DeprecationWarning`` and ``PendingDeprecationWarning`` are now shown by default if no other warning filter is
-configured. This makes pytest compliant with
+configured. This makes pytest more compliant with
-`PEP-0506 <https://www.python.org/dev/peps/pep-0565/#recommended-filter-settings-for-test-runners>`_.
+`PEP-0506 <https://www.python.org/dev/peps/pep-0565/#recommended-filter-settings-for-test-runners>`_. See
+`the docs <https://docs.pytest.org/en/latest/warnings.html#deprecationwarning-and-pendingdeprecationwarning>`_ for
+more info.

doc/en/warnings.rst

@@ -82,6 +82,21 @@ Disabling warning summary
 Although not recommended, you can use the ``--disable-warnings`` command-line option to suppress the
 warning summary entirely from the test run output.
 
+Disabling warning capture entirely
+----------------------------------
+
+This plugin is enabled by default but can be disabled entirely in your ``pytest.ini`` file with:
+
+    .. code-block:: ini
+
+        [pytest]
+        addopts = -p no:warnings
+
+Or passing ``-p no:warnings`` in the command-line. This might be useful if your test suites handles warnings
+using an external system.
+
+
+.. _`deprecation-warnings`:
 
 DeprecationWarning and PendingDeprecationWarning
 ------------------------------------------------
@@ -89,11 +104,10 @@ DeprecationWarning and PendingDeprecationWarning
 .. versionadded:: 3.8
 
 By default pytest will display ``DeprecationWarning`` and ``PendingDeprecationWarning`` if no other warning filters
-are configured. This complies with `PEP-0506 <https://www.python.org/dev/peps/pep-0565/#recommended-filter-settings-for-test-runners>`_ which suggests that those warnings should
+are configured.
-be shown by default by test runners.
 
-To disable this behavior, you might define any warnings filter either in the command-line or in the ini file, but
+To disable showing ``DeprecationWarning`` and ``PendingDeprecationWarning`` warnings, you might define any warnings
-if you don't have any other warnings to filter you can use:
+filter either in the command-line or in the ini file, or you can use:
 
 .. code-block:: ini
 
@@ -102,6 +116,13 @@ if you don't have any other warnings to filter you can use:
         ignore::DeprecationWarning
         ignore::PendingDeprecationWarning
 
+.. note::
+    This makes pytest more compliant with `PEP-0506 <https://www.python.org/dev/peps/pep-0565/#recommended-filter-settings-for-test-runners>`_ which suggests that those warnings should
+    be shown by default by test runners, but pytest doesn't follow ``PEP-0506`` completely because resetting all
+    warning filters like suggested in the PEP will break existing test suites that configure warning filters themselves
+    by calling ``warnings.simplefilter`` (see issue `#2430 <https://github.com/pytest-dev/pytest/issues/2430>`_
+    for an example of that).
+
 
 .. _`filterwarnings`:
 
@@ -168,18 +189,6 @@ decorator or to all tests in a module by setting the ``pytestmark`` variable:
 .. _`pytest-warnings`: https://github.com/fschulze/pytest-warnings
 
 
-Disabling warning capture
--------------------------
-
-This feature is enabled by default but can be disabled entirely in your ``pytest.ini`` file with:
-
-    .. code-block:: ini
-
-        [pytest]
-        addopts = -p no:warnings
-
-Or passing ``-p no:warnings`` in the command-line.
-
 .. _`asserting warnings`:
 
 .. _assertwarnings: