Display --help/--version with ArgumentErrors

changelog/2753.feature.rst

@@ -0,0 +1 @@
+Usage errors from argparse are mapped to pytest's ``UsageError``.

changelog/4651.bugfix.rst

@@ -0,0 +1 @@
+``--help`` and ``--version`` are handled with ``UsageError``.

src/_pytest/config/__init__.py

@@ -648,8 +648,27 @@ def get_terminal_writer(self):
         return self.pluginmanager.get_plugin("terminalreporter")._tw
 
     def pytest_cmdline_parse(self, pluginmanager, args):
-        # REF1 assert self == pluginmanager.config, (self, pluginmanager.config)
-        self.parse(args)
+        try:
+            self.parse(args)
+        except UsageError:
+
+            # Handle --version and --help here in a minimal fashion.
+            # This gets done via helpconfig normally, but its
+            # pytest_cmdline_main is not called in case of errors.
+            if getattr(self.option, "version", False) or "--version" in args:
+                from _pytest.helpconfig import showversion
+
+                showversion(self)
+            elif (
+                getattr(self.option, "help", False) or "--help" in args or "-h" in args
+            ):
+                self._parser._getparser().print_help()
+                sys.stdout.write(
+                    "\nNOTE: displaying only minimal help due to UsageError.\n\n"
+                )
+
+            raise
+
         return self
 
     def notify_exception(self, excinfo, option=None):
@@ -760,21 +779,32 @@ def _mark_plugins_for_rewrite(self, hook):
         for name in _iter_rewritable_modules(package_files):
             hook.mark_rewrite(name)
 
-    def _validate_args(self, args):
+    def _validate_args(self, args, via):
         """Validate known args."""
-        self._parser.parse_known_and_unknown_args(
-            args, namespace=copy.copy(self.option)
-        )
+        self._parser._config_source_hint = via
+        try:
+            self._parser.parse_known_and_unknown_args(
+                args, namespace=copy.copy(self.option)
+            )
+        finally:
+            del self._parser._config_source_hint
+
         return args
 
     def _preparse(self, args, addopts=True):
         if addopts:
             env_addopts = os.environ.get("PYTEST_ADDOPTS", "")
             if len(env_addopts):
-                args[:] = self._validate_args(shlex.split(env_addopts)) + args
+                args[:] = (
+                    self._validate_args(shlex.split(env_addopts), "via PYTEST_ADDOPTS")
+                    + args
+                )
         self._initini(args)
         if addopts:
-            args[:] = self._validate_args(self.getini("addopts")) + args
+            args[:] = (
+                self._validate_args(self.getini("addopts"), "via addopts config") + args
+            )
+
         self._checkversion()
         self._consider_importhook(args)
         self.pluginmanager.consider_preparse(args)

src/_pytest/config/argparsing.py

@@ -1,12 +1,10 @@
 import argparse
-import sys as _sys
 import warnings
-from gettext import gettext as _
 
 import py
 import six
 
-from ..main import EXIT_USAGEERROR
+from _pytest.config.exceptions import UsageError
 
 FILE_OR_DIR = "file_or_dir"
 
@@ -337,14 +335,13 @@ def __init__(self, parser, extra_info=None, prog=None):
         self.extra_info = extra_info
 
     def error(self, message):
-        """error(message: string)
-
-        Prints a usage message incorporating the message to stderr and
-        exits.
-        Overrides the method in parent class to change exit code"""
-        self.print_usage(_sys.stderr)
-        args = {"prog": self.prog, "message": message}
-        self.exit(EXIT_USAGEERROR, _("%(prog)s: error: %(message)s\n") % args)
+        """Transform argparse error message into UsageError."""
+        msg = "%s: error: %s" % (self.prog, message)
+
+        if hasattr(self._parser, "_config_source_hint"):
+            msg = "%s (%s)" % (msg, self._parser._config_source_hint)
+
+        raise UsageError(self.format_usage() + msg)
 
     def parse_args(self, args=None, namespace=None):
         """allow splitting of positional arguments"""

src/_pytest/helpconfig.py

@@ -118,16 +118,20 @@ def unset_tracing():
         config.add_cleanup(unset_tracing)
 
 
+def showversion(config):
+    p = py.path.local(pytest.__file__)
+    sys.stderr.write(
+        "This is pytest version %s, imported from %s\n" % (pytest.__version__, p)
+    )
+    plugininfo = getpluginversioninfo(config)
+    if plugininfo:
+        for line in plugininfo:
+            sys.stderr.write(line + "\n")
+
+
 def pytest_cmdline_main(config):
     if config.option.version:
-        p = py.path.local(pytest.__file__)
-        sys.stderr.write(
-            "This is pytest version %s, imported from %s\n" % (pytest.__version__, p)
-        )
-        plugininfo = getpluginversioninfo(config)
-        if plugininfo:
-            for line in plugininfo:
-                sys.stderr.write(line + "\n")
+        showversion(config)
         return 0
     elif config.option.help:
         config._do_configure()

testing/test_config.py

@@ -8,10 +8,12 @@
 import _pytest._code
 import pytest
 from _pytest.config import _iter_rewritable_modules
+from _pytest.config.exceptions import UsageError
 from _pytest.config.findpaths import determine_setup
 from _pytest.config.findpaths import get_common_ancestor
 from _pytest.config.findpaths import getcfg
 from _pytest.main import EXIT_NOTESTSCOLLECTED
+from _pytest.main import EXIT_USAGEERROR
 
 
 class TestParseIni(object):
@@ -1031,9 +1033,12 @@ def test_addopts_from_env_not_concatenated(self, monkeypatch):
 
         monkeypatch.setenv("PYTEST_ADDOPTS", "-o")
         config = get_config()
-        with pytest.raises(SystemExit) as excinfo:
+        with pytest.raises(UsageError) as excinfo:
             config._preparse(["cache_dir=ignored"], addopts=True)
-        assert excinfo.value.args[0] == _pytest.main.EXIT_USAGEERROR
+        assert (
+            "error: argument -o/--override-ini: expected one argument (via PYTEST_ADDOPTS)"
+            in excinfo.value.args[0]
+        )
 
     def test_addopts_from_ini_not_concatenated(self, testdir):
         """addopts from ini should not take values from normal args (#4265)."""
@@ -1046,7 +1051,7 @@ def test_addopts_from_ini_not_concatenated(self, testdir):
         result = testdir.runpytest("cache_dir=ignored")
         result.stderr.fnmatch_lines(
             [
-                "%s: error: argument -o/--override-ini: expected one argument"
+                "%s: error: argument -o/--override-ini: expected one argument (via addopts config)"
                 % (testdir.request.config._parser.optparser.prog,)
             ]
         )
@@ -1083,3 +1088,68 @@ def test():
         result = testdir.runpytest("-o", "foo=1", "-o", "bar=0", "test_foo.py")
         assert "ERROR:" not in result.stderr.str()
         result.stdout.fnmatch_lines(["collected 1 item", "*= 1 passed in *="])
+
+
+def test_help_via_addopts(testdir):
+    testdir.makeini(
+        """
+        [pytest]
+        addopts = --unknown-option-should-allow-for-help --help
+    """
+    )
+    result = testdir.runpytest()
+    assert result.ret == 0
+    result.stdout.fnmatch_lines(
+        [
+            "usage: *",
+            "positional arguments:",
+            # Displays full/default help.
+            "to see available markers type: pytest --markers",
+        ]
+    )
+
+
+def test_help_and_version_after_argument_error(testdir):
+    testdir.makeconftest(
+        """
+        def validate(arg):
+            raise argparse.ArgumentTypeError("argerror")
+
+        def pytest_addoption(parser):
+            group = parser.getgroup('cov')
+            group.addoption(
+                "--invalid-option-should-allow-for-help",
+                type=validate,
+            )
+        """
+    )
+    testdir.makeini(
+        """
+        [pytest]
+        addopts = --invalid-option-should-allow-for-help
+    """
+    )
+    result = testdir.runpytest("--help")
+    result.stdout.fnmatch_lines(
+        [
+            "usage: *",
+            "positional arguments:",
+            "NOTE: displaying only minimal help due to UsageError.",
+        ]
+    )
+    result.stderr.fnmatch_lines(
+        [
+            "ERROR: usage: *",
+            "%s: error: argument --invalid-option-should-allow-for-help: expected one argument"
+            % (testdir.request.config._parser.optparser.prog,),
+        ]
+    )
+    # Does not display full/default help.
+    assert "to see available markers type: pytest --markers" not in result.stdout.lines
+    assert result.ret == EXIT_USAGEERROR
+
+    result = testdir.runpytest("--version")
+    result.stderr.fnmatch_lines(
+        ["*pytest*{}*imported from*".format(pytest.__version__)]
+    )
+    assert result.ret == EXIT_USAGEERROR

testing/test_parseopt.py

@@ -11,6 +11,7 @@
 
 import pytest
 from _pytest.config import argparsing as parseopt
+from _pytest.config.exceptions import UsageError
 
 
 @pytest.fixture
@@ -19,11 +20,9 @@ def parser():
 
 
 class TestParser(object):
-    def test_no_help_by_default(self, capsys):
+    def test_no_help_by_default(self):
         parser = parseopt.Parser(usage="xyz")
-        pytest.raises(SystemExit, lambda: parser.parse(["-h"]))
-        out, err = capsys.readouterr()
-        assert err.find("error: unrecognized arguments") != -1
+        pytest.raises(UsageError, lambda: parser.parse(["-h"]))
 
     def test_custom_prog(self, parser):
         """Custom prog can be set for `argparse.ArgumentParser`."""