Implement hack to issue warnings during config

Once we can capture warnings during the config stage, we can
then get rid of this function

Related to #2891

Author: nicoddemus

doc/en/reference.rst

@@ -611,6 +611,8 @@ Session related reporting hooks:
 .. autofunction:: pytest_terminal_summary
 .. autofunction:: pytest_fixture_setup
 .. autofunction:: pytest_fixture_post_finalizer
+.. autofunction:: pytest_logwarning
+.. autofunction:: pytest_warning_captured
 
 And here is the central hook for reporting about
 test execution:

src/_pytest/config/__init__.py

@@ -154,7 +154,7 @@ def get_plugin_manager():
 
 
 def _prepareconfig(args=None, plugins=None):
-    warning = None
+    warning_msg = None
     if args is None:
         args = sys.argv[1:]
     elif isinstance(args, py.path.local):
@@ -165,7 +165,7 @@ def _prepareconfig(args=None, plugins=None):
         args = shlex.split(args, posix=sys.platform != "win32")
         from _pytest import deprecated
 
-        warning = deprecated.MAIN_STR_ARGS
+        warning_msg = deprecated.MAIN_STR_ARGS
     config = get_config()
     pluginmanager = config.pluginmanager
     try:
@@ -175,10 +175,11 @@ def _prepareconfig(args=None, plugins=None):
                     pluginmanager.consider_pluginarg(plugin)
                 else:
                     pluginmanager.register(plugin)
-        if warning:
+        if warning_msg:
             from _pytest.warning_types import PytestWarning
+            from _pytest.warnings import _issue_config_warning
 
-            warnings.warn(warning, PytestWarning)
+            _issue_config_warning(PytestWarning(warning_msg), config=config)
         return pluginmanager.hook.pytest_cmdline_parse(
             pluginmanager=pluginmanager, args=args
         )
@@ -696,6 +697,7 @@ def _initini(self, args):
             ns.inifilename,
             ns.file_or_dir + unknown_args,
             rootdir_cmd_arg=ns.rootdir or None,
+            config=self,
         )
         self.rootdir, self.inifile, self.inicfg = r
         self._parser.extra_info["rootdir"] = self.rootdir

src/_pytest/config/findpaths.py

@@ -10,15 +10,12 @@ def exists(path, ignore=EnvironmentError):
         return False
 
 
-def getcfg(args):
+def getcfg(args, config=None):
     """
     Search the list of arguments for a valid ini-file for pytest,
     and return a tuple of (rootdir, inifile, cfg-dict).
 
-    note: warnfunc is an optional function used to warn
-        about ini-files that use deprecated features.
-        This parameter should be removed when pytest
-        adopts standard deprecation warnings (#1804).
+    note: config is optional and used only to issue warnings explicitly (#2891).
     """
     from _pytest.deprecated import CFG_PYTEST_SECTION
 
@@ -34,13 +31,15 @@ def getcfg(args):
                 if exists(p):
                     iniconfig = py.iniconfig.IniConfig(p)
                     if "pytest" in iniconfig.sections:
-                        if inibasename == "setup.cfg":
-                            import warnings
+                        if inibasename == "setup.cfg" and config is not None:
+                            from _pytest.warnings import _issue_config_warning
                             from _pytest.warning_types import RemovedInPytest4Warning
 
-                            warnings.warn(
-                                CFG_PYTEST_SECTION.format(filename=inibasename),
-                                RemovedInPytest4Warning,
+                            _issue_config_warning(
+                                RemovedInPytest4Warning(
+                                    CFG_PYTEST_SECTION.format(filename=inibasename)
+                                ),
+                                config=config,
                             )
                         return base, p, iniconfig["pytest"]
                     if (
@@ -99,7 +98,7 @@ def get_dir_from_path(path):
     return [get_dir_from_path(path) for path in possible_paths if path.exists()]
 
 
-def determine_setup(inifile, args, rootdir_cmd_arg=None):
+def determine_setup(inifile, args, rootdir_cmd_arg=None, config=None):
     dirs = get_dirs_from_args(args)
     if inifile:
         iniconfig = py.iniconfig.IniConfig(inifile)
@@ -109,28 +108,30 @@ def determine_setup(inifile, args, rootdir_cmd_arg=None):
         for section in sections:
             try:
                 inicfg = iniconfig[section]
-                if is_cfg_file and section == "pytest":
-                    from _pytest.warning_types import RemovedInPytest4Warning
+                if is_cfg_file and section == "pytest" and config is not None:
                     from _pytest.deprecated import CFG_PYTEST_SECTION
-                    import warnings
+                    from _pytest.warning_types import RemovedInPytest4Warning
+                    from _pytest.warnings import _issue_config_warning
 
-                    warnings.warn(
-                        CFG_PYTEST_SECTION.format(filename=str(inifile)),
-                        RemovedInPytest4Warning,
+                    _issue_config_warning(
+                        RemovedInPytest4Warning(
+                            CFG_PYTEST_SECTION.format(filename=str(inifile))
+                        ),
+                        config,
                     )
                 break
             except KeyError:
                 inicfg = None
         rootdir = get_common_ancestor(dirs)
     else:
         ancestor = get_common_ancestor(dirs)
-        rootdir, inifile, inicfg = getcfg([ancestor])
+        rootdir, inifile, inicfg = getcfg([ancestor], config=config)
         if rootdir is None:
             for rootdir in ancestor.parts(reverse=True):
                 if rootdir.join("setup.py").exists():
                     break
             else:
-                rootdir, inifile, inicfg = getcfg(dirs)
+                rootdir, inifile, inicfg = getcfg(dirs, config=config)
                 if rootdir is None:
                     rootdir = get_common_ancestor([py.path.local(), ancestor])
                     is_fs_root = os.path.splitdrive(str(rootdir))[1] == "/"

src/_pytest/hookspec.py

@@ -526,7 +526,17 @@ def pytest_terminal_summary(terminalreporter, exitstatus):
 
 @hookspec(historic=True)
 def pytest_logwarning(message, code, nodeid, fslocation):
-    """ process a warning specified by a message, a code string,
+    """
+    .. deprecated:: 3.8
+
+        This hook is will stop working in a future release.
+
+        pytest no longer triggers this hook, but the
+        terminal writer still implements it to display warnings issued by
+        :meth:`_pytest.config.Config.warn` and :meth:`_pytest.nodes.Node.warn`. Calling those functions will be
+        an error in future releases.
+
+    process a warning specified by a message, a code string,
     a nodeid and fslocation (both of which may be None
     if the warning is not tied to a particular node/location).
 
@@ -538,14 +548,16 @@ def pytest_logwarning(message, code, nodeid, fslocation):
 @hookspec(historic=True)
 def pytest_warning_captured(warning_message, when, item):
     """
-    Process a warning captured by the internal pytest plugin.
+    Process a warning captured by the internal pytest warnings plugin.
 
     :param warnings.WarningMessage warning_message:
         The captured warning. This is the same object produced by :py:func:`warnings.catch_warnings`, and contains
         the same attributes as the parameters of :py:func:`warnings.showwarning`.
 
     :param str when:
         Indicates when the warning was captured. Possible values:
+
+        * ``"config"``: during pytest configuration/initialization stage.
         * ``"collect"``: during test collection.
         * ``"runtest"``: during test execution.
 

src/_pytest/resultlog.py

@@ -31,10 +31,10 @@ def pytest_configure(config):
         config.pluginmanager.register(config._resultlog)
 
         from _pytest.deprecated import RESULT_LOG
-        import warnings
         from _pytest.warning_types import RemovedInPytest4Warning
+        from _pytest.warnings import _issue_config_warning
 
-        warnings.warn(RESULT_LOG, RemovedInPytest4Warning)
+        _issue_config_warning(RemovedInPytest4Warning(RESULT_LOG), config)
 
 
 def pytest_unconfigure(config):

src/_pytest/warnings.py

@@ -146,3 +146,20 @@ def pytest_terminal_summary(terminalreporter):
     config = terminalreporter.config
     with catch_warnings_for_item(config=config, ihook=config.hook, item=None):
         yield
+
+
+def _issue_config_warning(warning, config):
+    """
+    This function should be used instead of calling ``warnings.warn`` directly when we are in the "configure" stage:
+    at this point the actual options might not have been set, so we manually trigger the pytest_warning_captured
+    hook so we can display this warnings in the terminal. This is a hack until we can sort out #2891.
+
+    :param warning: the warning instance.
+    :param config:
+    """
+    with warnings.catch_warnings(record=True) as records:
+        warnings.simplefilter("always", type(warning))
+        warnings.warn(warning, stacklevel=2)
+    config.hook.pytest_warning_captured.call_historic(
+        kwargs=dict(warning_message=records[0], when="config", item=None)
+    )

testing/deprecated_test.py

@@ -54,9 +54,6 @@ def test_funcarg_prefix(value):
 
 
 @pytest.mark.filterwarnings("default")
-@pytest.mark.xfail(
-    reason="#2891 need to handle warnings during pre-config", strict=True
-)
 def test_pytest_setup_cfg_deprecated(testdir):
     testdir.makefile(
         ".cfg",
@@ -72,9 +69,6 @@ def test_pytest_setup_cfg_deprecated(testdir):
 
 
 @pytest.mark.filterwarnings("default")
-@pytest.mark.xfail(
-    reason="#2891 need to handle warnings during pre-config", strict=True
-)
 def test_pytest_custom_cfg_deprecated(testdir):
     testdir.makefile(
         ".cfg",
@@ -89,18 +83,15 @@ def test_pytest_custom_cfg_deprecated(testdir):
     )
 
 
-@pytest.mark.xfail(
-    reason="#2891 need to handle warnings during pre-config", strict=True
-)
-def test_str_args_deprecated(tmpdir, testdir):
+def test_str_args_deprecated(tmpdir):
     """Deprecate passing strings to pytest.main(). Scheduled for removal in pytest-4.0."""
     from _pytest.main import EXIT_NOTESTSCOLLECTED
 
     warnings = []
 
     class Collect(object):
-        def pytest_logwarning(self, message):
-            warnings.append(message)
+        def pytest_warning_captured(self, warning_message):
+            warnings.append(str(warning_message.message))
 
     ret = pytest.main("%s -x" % tmpdir, plugins=[Collect()])
     msg = (
@@ -116,9 +107,6 @@ def test_getfuncargvalue_is_deprecated(request):
 
 
 @pytest.mark.filterwarnings("default")
-@pytest.mark.xfail(
-    reason="#2891 need to handle warnings during pre-config", strict=True
-)
 def test_resultlog_is_deprecated(testdir):
     result = testdir.runpytest("--help")
     result.stdout.fnmatch_lines(["*DEPRECATED path for machine-readable result log*"])