fix issue358 -- introduce new pytest_load_initial_conftests hook and make capturing initialization use it, relying on a new (somewhat internal) parser.parse_known_args() method.

This also addresses issue359 -- plugins like pytest-django could implement a pytest_load_initial_conftests hook like the capture plugin.

CHANGELOG

@@ -75,6 +75,9 @@ new features:
 - fix issue 308 - allow to mark/xfail/skip individual parameter sets
   when parametrizing.  Thanks Brianna Laugher.
 
+- call new experimental pytest_load_initial_conftests hook to allow
+  3rd party plugins to do something before a conftest is loaded.
+
 Bug fixes:
 
 - pytest now uses argparse instead of optparse (thanks Anthon) which 

_pytest/capture.py

@@ -1,6 +1,7 @@
 """ per-test stdout/stderr capturing mechanisms, ``capsys`` and ``capfd`` function arguments.  """
 
 import pytest, py
+import sys
 import os
 
 def pytest_addoption(parser):
@@ -12,23 +13,34 @@ def pytest_addoption(parser):
         help="shortcut for --capture=no.")
 
 @pytest.mark.tryfirst
-def pytest_cmdline_parse(pluginmanager, args):
-    # we want to perform capturing already for plugin/conftest loading
-    if '-s' in args or "--capture=no" in args:
-        method = "no"
-    elif hasattr(os, 'dup') and '--capture=sys' not in args:
+def pytest_load_initial_conftests(early_config, parser, args, __multicall__):
+    ns = parser.parse_known_args(args)
+    method = ns.capture
+    if not method:
         method = "fd"
-    else:
+    if method == "fd" and not hasattr(os, "dup"):
         method = "sys"
     capman = CaptureManager(method)
-    pluginmanager.register(capman, "capturemanager")
+    early_config.pluginmanager.register(capman, "capturemanager")
     # make sure that capturemanager is properly reset at final shutdown
     def teardown():
         try:
             capman.reset_capturings()
         except ValueError:
             pass
-    pluginmanager.add_shutdown(teardown)
+    early_config.pluginmanager.add_shutdown(teardown)
+
+    # finally trigger conftest loading but while capturing (issue93)
+    capman.resumecapture()
+    try:
+        try:
+            return __multicall__.execute()
+        finally:
+            out, err = capman.suspendcapture()
+    except:
+        sys.stdout.write(out)
+        sys.stderr.write(err)
+        raise
 
 def addouterr(rep, outerr):
     for secname, content in zip(["out", "err"], outerr):
@@ -89,7 +101,6 @@ class CaptureManager:
         for name, cap in self._method2capture.items():
             cap.reset()
 
-
     def resumecapture_item(self, item):
         method = self._getmethod(item.config, item.fspath)
         if not hasattr(item, 'outerr'):

_pytest/config.py

@@ -141,8 +141,14 @@ class Parser:
         self._anonymous.addoption(*opts, **attrs)
 
     def parse(self, args):
-        from _pytest._argcomplete import try_argcomplete, filescompleter
-        self.optparser = optparser = MyOptionParser(self)
+        from _pytest._argcomplete import try_argcomplete
+        self.optparser = self._getparser()
+        try_argcomplete(self.optparser)
+        return self.optparser.parse_args([str(x) for x in args])
+
+    def _getparser(self):
+        from _pytest._argcomplete import filescompleter
+        optparser = MyOptionParser(self)
         groups = self._groups + [self._anonymous]
         for group in groups:
             if group.options:
@@ -155,8 +161,7 @@ class Parser:
         # bash like autocompletion for dirs (appending '/')
         optparser.add_argument(FILE_OR_DIR, nargs='*'
                                ).completer=filescompleter
-        try_argcomplete(self.optparser)
-        return self.optparser.parse_args([str(x) for x in args])
+        return optparser
 
     def parse_setoption(self, args, option):
         parsedoption = self.parse(args)
@@ -164,6 +169,11 @@ class Parser:
             setattr(option, name, value)
         return getattr(parsedoption, FILE_OR_DIR)
 
+    def parse_known_args(self, args):
+        optparser = self._getparser()
+        args = [str(x) for x in args]
+        return optparser.parse_known_args(args)[0]
+
     def addini(self, name, help, type=None, default=None):
         """ register an ini-file option.
 
@@ -635,9 +645,6 @@ class Config(object):
         """ constructor useable for subprocesses. """
         pluginmanager = get_plugin_manager()
         config = pluginmanager.config
-        # XXX slightly crude way to initialize capturing
-        import _pytest.capture
-        _pytest.capture.pytest_cmdline_parse(config.pluginmanager, args)
         config._preparse(args, addopts=False)
         config.option.__dict__.update(option_dict)
         for x in config.option.plugins:
@@ -663,21 +670,9 @@ class Config(object):
         plugins += self._conftest.getconftestmodules(fspath)
         return plugins
 
-    def _setinitialconftest(self, args):
-        # capture output during conftest init (#issue93)
-        # XXX introduce load_conftest hook to avoid needing to know
-        # about capturing plugin here
-        capman = self.pluginmanager.getplugin("capturemanager")
-        capman.resumecapture()
-        try:
-            try:
-                self._conftest.setinitial(args)
-            finally:
-                out, err = capman.suspendcapture() # logging might have got it
-        except:
-            sys.stdout.write(out)
-            sys.stderr.write(err)
-            raise
+    def pytest_load_initial_conftests(self, parser, args):
+        self._conftest.setinitial(args)
+    pytest_load_initial_conftests.trylast = True
 
     def _initini(self, args):
         self.inicfg = getcfg(args, ["pytest.ini", "tox.ini", "setup.cfg"])
@@ -692,9 +687,8 @@ class Config(object):
         self.pluginmanager.consider_preparse(args)
         self.pluginmanager.consider_setuptools_entrypoints()
         self.pluginmanager.consider_env()
-        self._setinitialconftest(args)
-        if addopts:
-            self.hook.pytest_cmdline_preparse(config=self, args=args)
+        self.hook.pytest_load_initial_conftests(early_config=self,
+            args=args, parser=self._parser)
 
     def _checkversion(self):
         import pytest
@@ -715,6 +709,8 @@ class Config(object):
                 "can only parse cmdline args at most once per Config object")
         self._origargs = args
         self._preparse(args)
+        # XXX deprecated hook:
+        self.hook.pytest_cmdline_preparse(config=self, args=args)
         self._parser.hints.extend(self.pluginmanager._hints)
         args = self._parser.parse_setoption(args, self.option)
         if not args:

_pytest/hookspec.py

@@ -20,7 +20,7 @@ def pytest_cmdline_parse(pluginmanager, args):
 pytest_cmdline_parse.firstresult = True
 
 def pytest_cmdline_preparse(config, args):
-    """modify command line arguments before option parsing. """
+    """(deprecated) modify command line arguments before option parsing. """
 
 def pytest_addoption(parser):
     """register argparse-style options and ini-style config values.
@@ -52,6 +52,10 @@ def pytest_cmdline_main(config):
     implementation will invoke the configure hooks and runtest_mainloop. """
 pytest_cmdline_main.firstresult = True
 
+def pytest_load_initial_conftests(args, early_config, parser):
+    """ implements loading initial conftests.
+    """
+
 def pytest_configure(config):
     """ called after command line options have been parsed
         and all plugins and initial conftest files been loaded.

testing/test_capture.py

@@ -484,3 +484,13 @@ def test_capture_conftest_runtest_setup(testdir):
     result = testdir.runpytest()
     assert result.ret == 0
     assert 'hello19' not in result.stdout.str()
+
+def test_capture_early_option_parsing(testdir):
+    testdir.makeconftest("""
+        def pytest_runtest_setup():
+            print ("hello19")
+    """)
+    testdir.makepyfile("def test_func(): pass")
+    result = testdir.runpytest("-vs")
+    assert result.ret == 0
+    assert 'hello19' in result.stdout.str()

testing/test_config.py

@@ -335,3 +335,18 @@ def test_notify_exception(testdir, capfd):
     out, err = capfd.readouterr()
     assert not err
 
+
+def test_load_initial_conftest_last_ordering(testdir):
+    from _pytest.config  import get_plugin_manager
+    pm = get_plugin_manager()
+    class My:
+        def pytest_load_initial_conftests(self):
+            pass
+    m = My()
+    pm.register(m)
+    l = pm.listattr("pytest_load_initial_conftests")
+    assert l[-1].__module__ == "_pytest.capture"
+    assert l[-2] == m.pytest_load_initial_conftests
+    assert l[-3].__module__ == "_pytest.config"
+
+

testing/test_parseopt.py

@@ -101,6 +101,12 @@ class TestParser:
         args = parser.parse([py.path.local()])
         assert getattr(args, parseopt.FILE_OR_DIR)[0] == py.path.local()
 
+    def test_parse_known_args(self, parser):
+        args = parser.parse_known_args([py.path.local()])
+        parser.addoption("--hello", action="store_true")
+        ns = parser.parse_known_args(["x", "--y", "--hello", "this"])
+        assert ns.hello
+
     def test_parse_will_set_default(self, parser):
         parser.addoption("--hello", dest="hello", default="x", action="store")
         option = parser.parse([])