Fix -o behavior to no longer swallow all remaining options

The current behavior was too error-prone because a "-o" option would
swallow all the following non-option parameters:

  pytest -o foo=bar path/to/test.py

path/to/test.py would be captured by the -o option, and would fail
because "path/to/test.py" is not in the format "key=value".

_pytest/config.py

@@ -1188,19 +1188,15 @@ class Config(object):
 
     def _get_override_ini_value(self, name):
         value = None
-        # override_ini is a list of list, to support both -o foo1=bar1 foo2=bar2 and
-        # and -o foo1=bar1 -o foo2=bar2 options
-        # always use the last item if multiple value set for same ini-name,
+        # override_ini is a list of "ini=value" options
+        # always use the last item if multiple values are set for same ini-name,
         # e.g. -o foo=bar1 -o foo=bar2 will set foo to bar2
-        first_override_set = False
-        for ini_config_list in self._override_ini:
-            for ini_config in ini_config_list:
-                try:
-                    (key, user_ini_value) = ini_config.split("=", 1)
-                    first_override_set = True
-                except ValueError:
-                    if not first_override_set:
-                        raise UsageError("-o/--override-ini expects option=value style.")
+        for ini_config in self._override_ini:
+            try:
+                key, user_ini_value = ini_config.split("=", 1)
+            except ValueError:
+                raise UsageError("-o/--override-ini expects option=value style.")
+            else:
                 if key == name:
                     value = user_ini_value
         return value

_pytest/helpconfig.py

@@ -57,9 +57,9 @@ def pytest_addoption(parser):
                     action="store_true", dest="debug", default=False,
                     help="store internal tracing debug information in 'pytestdebug.log'.")
     group._addoption(
-        '-o', '--override-ini', nargs='*', dest="override_ini",
+        '-o', '--override-ini', dest="override_ini",
         action="append",
-        help="override config option with option=value style, e.g. `-o xfail_strict=True`.")
+        help='override ini option with "option=value" style, e.g. `-o xfail_strict=True -o cache_dir=cache`.')
 
 
 @pytest.hookimpl(hookwrapper=True)

changelog/3103.bugfix

@@ -1 +1 @@
-Fix ``UsageError`` being raised when specifying ``-o/--override`` command-line option followed by a test path.
+**Incompatible change**: ``-o/--override`` option no longer eats all the remaining options, which can lead to surprising behavior: for example, ``pytest -o foo=1 /path/to/test.py`` would fail because ``/path/to/test.py`` would be considered as part of the ``-o`` command-line argument. One consequence of this is that now multiple configuration overrides need multiple ``-o`` flags: ``pytest -o foo=1 -o bar=2``.

doc/en/customize.rst

@@ -152,11 +152,25 @@ above will show verbose output because ``-v`` overwrites ``-q``.
 Builtin configuration file options
 ----------------------------------------------
 
+Here is a list of builtin configuration options that may be written in a ``pytest.ini``, ``tox.ini`` or ``setup.cfg``
+file, usually located at the root of your repository. All options must be under a ``[pytest]`` section
+(``[tool:pytest]`` for ``setup.cfg`` files).
+
+Configuration file options may be overwritten in the command-line by using ``-o/--override``, which can also be
+passed multiple times. The expected format is ``name=value``. For example::
+
+   pytest -o console_output_style=classic -o cache_dir=/tmp/mycache
+
+
 .. confval:: minversion
 
    Specifies a minimal pytest version required for running tests.
 
-        minversion = 2.1  # will fail if we run with pytest-2.0
+   .. code-block:: ini
+
+        # content of pytest.ini
+        [pytest]
+        minversion = 3.0  # will fail if we run with pytest-2.8
 
 .. confval:: addopts
 
@@ -165,6 +179,7 @@ Builtin configuration file options
 
    .. code-block:: ini
 
+        # content of pytest.ini
         [pytest]
         addopts = --maxfail=2 -rf  # exit after 2 failures, report fail info
 

testing/test_config.py

@@ -781,16 +781,18 @@ class TestOverrideIniArgs(object):
         testdir.makeini("""
             [pytest]
             custom_option_1=custom_option_1
-            custom_option_2=custom_option_2""")
+            custom_option_2=custom_option_2
+        """)
         testdir.makepyfile("""
             def test_multiple_options(pytestconfig):
                 prefix = "custom_option"
                 for x in range(1, 5):
                     ini_value=pytestconfig.getini("%s_%d" % (prefix, x))
-                    print('\\nini%d:%s' % (x, ini_value))""")
+                    print('\\nini%d:%s' % (x, ini_value))
+        """)
         result = testdir.runpytest(
             "--override-ini", 'custom_option_1=fulldir=/tmp/user1',
-            'custom_option_2=url=/tmp/user2?a=b&d=e',
+            '-o', 'custom_option_2=url=/tmp/user2?a=b&d=e',
             "-o", 'custom_option_3=True',
             "-o", 'custom_option_4=no', "-s")
         result.stdout.fnmatch_lines(["ini1:fulldir=/tmp/user1",
@@ -853,24 +855,42 @@ class TestOverrideIniArgs(object):
             assert rootdir == tmpdir
             assert inifile is None
 
-    def test_addopts_before_initini(self, testdir, tmpdir, monkeypatch):
+    def test_addopts_before_initini(self, monkeypatch):
         cache_dir = '.custom_cache'
         monkeypatch.setenv('PYTEST_ADDOPTS', '-o cache_dir=%s' % cache_dir)
         from _pytest.config import get_config
         config = get_config()
         config._preparse([], addopts=True)
-        assert config._override_ini == [['cache_dir=%s' % cache_dir]]
+        assert config._override_ini == ['cache_dir=%s' % cache_dir]
 
-    def test_no_error_if_true_first_key_value_pair(self, testdir, request):
+    def test_override_ini_does_not_contain_paths(self):
+        """Check that -o no longer swallows all options after it (#3103)"""
+        from _pytest.config import get_config
+        config = get_config()
+        config._preparse(['-o', 'cache_dir=/cache', '/some/test/path'])
+        assert config._override_ini == ['cache_dir=/cache']
+
+    def test_multiple_override_ini_options(self, testdir, request):
         """Ensure a file path following a '-o' option does not generate an error (#3103)"""
-        testdir.makeini("""
-            [pytest]
-            xdist_strict=False
-        """)
-        testdir.makepyfile("""
-            def test():
-                pass
-        """)
-        result = testdir.runpytest('--override-ini', 'xdist_strict=True', '{}.py'.format(request.node.name))
+        testdir.makepyfile(**{
+            "conftest.py": """
+                def pytest_addoption(parser):
+                    parser.addini('foo', default=None, help='some option')
+                    parser.addini('bar', default=None, help='some option')
+            """,
+            "test_foo.py": """
+                def test(pytestconfig):
+                    assert pytestconfig.getini('foo') == '1'
+                    assert pytestconfig.getini('bar') == '0'
+            """,
+            "test_bar.py": """
+                def test():
+                    assert False
+            """,
+        })
+        result = testdir.runpytest('-o', 'foo=1', '-o', 'bar=0', 'test_foo.py')
         assert 'ERROR:' not in result.stderr.str()
-        result.stdout.fnmatch_lines('* 1 passed in *')
+        result.stdout.fnmatch_lines([
+            'collected 1 item',
+            '*= 1 passed in *=',
+        ])