-W now takes precedence over filters in ini files

Fix pytest-dev#3946

Author: nicoddemus

changelog/3946.bugfix.rst

@@ -0,0 +1,2 @@
+Warning filters passed as command line options using ``-W`` now take precedence over filters defined in ``ini``
+configuration files.

src/_pytest/warnings.py

@@ -67,17 +67,19 @@ def catch_warnings_for_item(config, ihook, when, item):
 
     Each warning captured triggers the ``pytest_warning_captured`` hook.
     """
-    args = config.getoption("pythonwarnings") or []
+    cmdline_filters = config.getoption("pythonwarnings") or []
     inifilters = config.getini("filterwarnings")
     with warnings.catch_warnings(record=True) as log:
-        filters_configured = args or inifilters or sys.warnoptions
-
-        for arg in args:
-            warnings._setoption(arg)
+        filters_configured = bool(cmdline_filters or inifilters or sys.warnoptions)
 
+        # filters should have this precedence: mark, cmdline options, ini
+        # filters should be applied in the inverse order of precedence
         for arg in inifilters:
             _setoption(warnings, arg)
 
+        for arg in cmdline_filters:
+            warnings._setoption(arg)
+
         if item is not None:
             for mark in item.iter_markers(name="filterwarnings"):
                 for arg in mark.args:

testing/test_warnings.py

@@ -430,6 +430,50 @@ def test_bar():
         )
 
 
+@pytest.mark.parametrize("ignore_on_cmdline", [True, False])
+def test_option_precedence_cmdline_over_ini(testdir, ignore_on_cmdline):
+    """filters defined in the command-line should take precedence over filters in ini files (#3946)."""
+    testdir.makeini(
+        """
+        [pytest]
+        filterwarnings = error
+    """
+    )
+    testdir.makepyfile(
+        """
+        import warnings
+        def test():
+            warnings.warn(UserWarning('hello'))
+    """
+    )
+    args = ["-W", "ignore"] if ignore_on_cmdline else []
+    result = testdir.runpytest(*args)
+    if ignore_on_cmdline:
+        result.stdout.fnmatch_lines(["* 1 passed in*"])
+    else:
+        result.stdout.fnmatch_lines(["* 1 failed in*"])
+
+
+def test_option_precedence_mark(testdir):
+    """Filters defined by marks should always take precedence (#3946)."""
+    testdir.makeini(
+        """
+        [pytest]
+        filterwarnings = ignore
+    """
+    )
+    testdir.makepyfile(
+        """
+        import pytest, warnings
+        @pytest.mark.filterwarnings('error')
+        def test():
+            warnings.warn(UserWarning('hello'))
+    """
+    )
+    result = testdir.runpytest("-W", "ignore")
+    result.stdout.fnmatch_lines(["* 1 failed in*"])
+
+
 class TestDeprecationWarningsByDefault:
     """
     Note: all pytest runs are executed in a subprocess so we don't inherit warning filters