Do not allow abbreviated arguments

changelog/1149.removal.rst

@@ -0,0 +1,7 @@
+Pytest no longer accepts prefixes of command-line arguments, for example
+typing ``pytest --doctest-mod`` inplace of ``--doctest-modules``.
+This was previously allowed where the ``ArgumentParser`` thought it was unambiguous,
+but this could be incorrect due to delayed parsing of options for plugins.
+See for example issues `#1149 <https://github.com/pytest-dev/pytest/issues/1149>`__,
+`#3413 <https://github.com/pytest-dev/pytest/issues/3413>`__, and
+`#4009 <https://github.com/pytest-dev/pytest/issues/4009>`__.

extra/get_issues.py

@@ -74,7 +74,7 @@ def report(issues):
 if __name__ == "__main__":
     import argparse
 
-    parser = argparse.ArgumentParser("process bitbucket issues")
+    parser = argparse.ArgumentParser("process bitbucket issues", allow_abbrev=False)
     parser.add_argument(
         "--refresh", action="store_true", help="invalidate cache, refresh issues"
     )

scripts/release.py

@@ -105,7 +105,7 @@ def changelog(version, write_out=False):
 
 def main():
     init(autoreset=True)
-    parser = argparse.ArgumentParser()
+    parser = argparse.ArgumentParser(allow_abbrev=False)
     parser.add_argument("version", help="Release version")
     options = parser.parse_args()
     pre_release(options.version)

src/_pytest/config/argparsing.py

@@ -1,5 +1,7 @@
 import argparse
+import sys
 import warnings
+from gettext import gettext
 
 import py
 
@@ -328,6 +330,7 @@ class MyOptionParser(argparse.ArgumentParser):
             usage=parser._usage,
             add_help=False,
             formatter_class=DropShorterLongHelpFormatter,
+            allow_abbrev=False,
         )
         # extra_info is a dict of (param -> value) to display if there's
         # an usage error to provide more contextual information to the user
@@ -355,6 +358,42 @@ class MyOptionParser(argparse.ArgumentParser):
             getattr(args, FILE_OR_DIR).extend(argv)
         return args
 
+    if sys.version_info[:2] < (3, 8):  # pragma: no cover
+        # Backport of https://github.com/python/cpython/pull/14316 so we can
+        # disable long --argument abbreviations without breaking short flags.
+        def _parse_optional(self, arg_string):
+            if not arg_string:
+                return None
+            if not arg_string[0] in self.prefix_chars:
+                return None
+            if arg_string in self._option_string_actions:
+                action = self._option_string_actions[arg_string]
+                return action, arg_string, None
+            if len(arg_string) == 1:
+                return None
+            if "=" in arg_string:
+                option_string, explicit_arg = arg_string.split("=", 1)
+                if option_string in self._option_string_actions:
+                    action = self._option_string_actions[option_string]
+                    return action, option_string, explicit_arg
+            if self.allow_abbrev or not arg_string.startswith("--"):
+                option_tuples = self._get_option_tuples(arg_string)
+                if len(option_tuples) > 1:
+                    msg = gettext(
+                        "ambiguous option: %(option)s could match %(matches)s"
+                    )
+                    options = ", ".join(option for _, option, _ in option_tuples)
+                    self.error(msg % {"option": arg_string, "matches": options})
+                elif len(option_tuples) == 1:
+                    option_tuple, = option_tuples
+                    return option_tuple
+            if self._negative_number_matcher.match(arg_string):
+                if not self._has_negative_number_optionals:
+                    return None
+            if " " in arg_string:
+                return None
+            return None, arg_string, None
+
 
 class DropShorterLongHelpFormatter(argparse.HelpFormatter):
     """shorten help for long options that differ only in extra hyphens

testing/acceptance_test.py

@@ -984,7 +984,7 @@ def test_zipimport_hook(testdir, tmpdir):
             "app/foo.py": """
             import pytest
             def main():
-                pytest.main(['--pyarg', 'foo'])
+                pytest.main(['--pyargs', 'foo'])
         """
         }
     )

testing/example_scripts/perf_examples/collect_stats/generate_folders.py

@@ -4,7 +4,7 @@ import pathlib
 HERE = pathlib.Path(__file__).parent
 TEST_CONTENT = (HERE / "template_test.py").read_bytes()
 
-parser = argparse.ArgumentParser()
+parser = argparse.ArgumentParser(allow_abbrev=False)
 parser.add_argument("numbers", nargs="*", type=int)
 
 

testing/test_capture.py

@@ -735,7 +735,7 @@ def test_capture_badoutput_issue412(testdir):
             assert 0
         """
     )
-    result = testdir.runpytest("--cap=fd")
+    result = testdir.runpytest("--capture=fd")
     result.stdout.fnmatch_lines(
         """
         *def test_func*

testing/test_parseopt.py

@@ -200,7 +200,7 @@ class TestParser:
 
     def test_drop_short_helper(self):
         parser = argparse.ArgumentParser(
-            formatter_class=parseopt.DropShorterLongHelpFormatter
+            formatter_class=parseopt.DropShorterLongHelpFormatter, allow_abbrev=False
         )
         parser.add_argument(
             "-t", "--twoword", "--duo", "--two-word", "--two", help="foo"
@@ -239,10 +239,8 @@ class TestParser:
         parser.addoption("--funcarg", "--func-arg", action="store_true")
         parser.addoption("--abc-def", "--abc-def", action="store_true")
         parser.addoption("--klm-hij", action="store_true")
-        args = parser.parse(["--funcarg", "--k"])
-        assert args.funcarg is True
-        assert args.abc_def is False
-        assert args.klm_hij is True
+        with pytest.raises(UsageError):
+            parser.parse(["--funcarg", "--k"])
 
     def test_drop_short_2(self, parser):
         parser.addoption("--func-arg", "--doit", action="store_true")

testing/test_pastebin.py

@@ -21,7 +21,7 @@ class TestPasteCapture:
                 pytest.skip("")
         """
         )
-        reprec = testdir.inline_run(testpath, "--paste=failed")
+        reprec = testdir.inline_run(testpath, "--pastebin=failed")
         assert len(pastebinlist) == 1
         s = pastebinlist[0]
         assert s.find("def test_fail") != -1