introduce a pytest_cmdline_processargs hook to modify/add dynamically to command line arguments.

CHANGELOG

@@ -1,6 +1,11 @@
 Changes between 2.0.0 and 2.0.1.dev1
 ----------------------------------------------
 
+- introduce a pytest_cmdline_processargs(args) hook
+  to allow dynamic computation of command line arguments.
+  This fixes a regression because py.test prior to 2.0
+  allowed to set command line options from conftest.py
+  files which so far pytest-2.0 only allowed from ini-files now.
 - fix issue7: assert failures in doctest modules.
   unexpected failures in doctests will not generally
   show nicer, i.e. within the doctest failing context.

_pytest/config.py

@@ -305,6 +305,8 @@ class Config(object):
         self.pluginmanager.consider_env()
         self._setinitialconftest(args)
         self.pluginmanager.do_addoption(self._parser)
+        if addopts:
+            self.hook.pytest_cmdline_processargs(config=self, args=args)
 
     def _checkversion(self):
         minver = self.inicfg.get('minversion', None)

_pytest/hookspec.py

@@ -19,6 +19,9 @@ def pytest_cmdline_parse(pluginmanager, args):
     """return initialized config object, parsing the specified args. """
 pytest_cmdline_parse.firstresult = True
 
+def pytest_cmdline_processargs(config, args):
+    """modify command line arguments before option parsing. """
+
 def pytest_addoption(parser):
     """add optparse-style options and ini-style config values via calls
     to ``parser.addoption`` and ``parser.addini(...)``.
@@ -202,7 +205,6 @@ def pytest_doctest_prepare_content(content):
     """ return processed content for a given doctest"""
 pytest_doctest_prepare_content.firstresult = True
 
-
 # -------------------------------------------------------------------------
 # error handling and internal debugging hooks
 # -------------------------------------------------------------------------

doc/Makefile

@@ -40,7 +40,7 @@ clean:
 	-rm -rf $(BUILDDIR)/*
 
 install: clean html
-	rsync -avz _build/html/ code:www-pytest/
+	rsync -avz _build/html/ code:www-pytest/2.0.1dev
 
 html:
 	$(SPHINXBUILD) -b html $(ALLSPHINXOPTS) $(BUILDDIR)/html

doc/example/simple.txt

@@ -138,11 +138,42 @@ let's run the full monty::
     E       assert 4 < 4
     
     test_compute.py:3: AssertionError
-    1 failed, 4 passed in 0.03 seconds
+    1 failed, 4 passed in 0.02 seconds
 
 As expected when running the full range of ``param1`` values
 we'll get an error on the last one.
 
+dynamically adding command line options
+--------------------------------------------------------------
+
+.. regendoc:wipe
+
+Through :confval:`addopts` you can statically add command line
+options for your project.  You can also dynamically modify
+the command line arguments before they get processed::
+
+    # content of conftest.py
+    import sys
+    def pytest_cmdline_processargs(args):
+        if 'xdist' in sys.modules: # pytest-xdist plugin
+            import multiprocessing
+            num = max(multiprocessing.cpu_count() / 2, 1)
+            args[:] = ["-n", str(num)] + args
+
+If you have the :ref:`xdist plugin <xdist>` installed
+you will now always perform test runs using a number
+of subprocesses close to your CPU. Running in an empty
+directory with the above conftest.py::
+
+    $ py.test
+    =========================== test session starts ============================
+    platform linux2 -- Python 2.6.5 -- pytest-2.0.1.dev3
+    gw0 I / gw1 I / gw2 I / gw3 I
+    gw0 [0] / gw1 [0] / gw2 [0] / gw3 [0]
+    
+    scheduling tests via LoadScheduling
+    
+    =============================  in 0.29 seconds =============================
 
 .. _`retrieved by hooks as item keywords`:
 
@@ -183,12 +214,12 @@ and when running it will see a skipped "slow" test::
 
     $ py.test -rs    # "-rs" means report details on the little 's'
     =========================== test session starts ============================
-    platform linux2 -- Python 2.6.5 -- pytest-2.0.0
+    platform linux2 -- Python 2.6.5 -- pytest-2.0.1.dev3
     collecting ... collected 2 items
     
     test_module.py .s
     ========================= short test summary info ==========================
-    SKIP [1] /tmp/doc-exec-479/conftest.py:9: need --runslow option to run
+    SKIP [1] /tmp/doc-exec-25/conftest.py:9: need --runslow option to run
     
     =================== 1 passed, 1 skipped in 0.02 seconds ====================
 
@@ -196,7 +227,7 @@ Or run it including the ``slow`` marked test::
 
     $ py.test --runslow
     =========================== test session starts ============================
-    platform linux2 -- Python 2.6.5 -- pytest-2.0.0
+    platform linux2 -- Python 2.6.5 -- pytest-2.0.1.dev3
     collecting ... collected 2 items
     
     test_module.py ..

doc/plugins.txt

@@ -271,6 +271,7 @@ initialisation, command line and configuration hooks
 
 .. currentmodule:: _pytest.hookspec
 
+.. autofunction:: pytest_cmdline_processargs
 .. autofunction:: pytest_cmdline_parse
 .. autofunction:: pytest_namespace
 .. autofunction:: pytest_addoption

testing/test_config.py

@@ -82,7 +82,6 @@ class TestConfigCmdlineParsing:
 
 
 class TestConfigAPI:
-
     def test_config_trace(self, testdir):
         config = testdir.Config()
         l = []
@@ -252,3 +251,14 @@ def test_plugin_preparse_prevents_setuptools_loading(testdir, monkeypatch):
     config = testdir.parseconfig("-p", "no:mytestplugin")
     plugin = config.pluginmanager.getplugin("mytestplugin")
     assert plugin == -1
+
+def test_cmdline_processargs_simple(testdir):
+    testdir.makeconftest("""
+        def pytest_cmdline_processargs(args):
+            args.append("-h")
+    """)
+    result = testdir.runpytest()
+    result.stdout.fnmatch_lines([
+        "*pytest*",
+        "*-h*",
+    ])