Allow bypassing the logging setup via the Python API

docs/changelog/1896.bugfix.rst

@@ -0,0 +1,2 @@
+Provide ``setup_logging`` flag to python API so that users can bypass logging handling if their application already
+performs this - by :user:`gaborbernat`.

src/virtualenv/__init__.py

@@ -1,9 +1,10 @@
 from __future__ import absolute_import, unicode_literals
 
-from .run import cli_run
+from .run import cli_run, session_via_cli
 from .version import __version__
 
 __all__ = (
     "__version__",
     "cli_run",
+    "session_via_cli",
 )

src/virtualenv/run/__init__.py

@@ -14,30 +14,39 @@
 from .plugin.seeders import SeederSelector
 
 
-def cli_run(args, options=None):
-    """Create a virtual environment given some command line interface arguments
+def cli_run(args, options=None, setup_logging=True):
+    """
+    Create a virtual environment given some command line interface arguments.
 
     :param args: the command line arguments
     :param options: passing in a ``VirtualEnvOptions`` object allows return of the parsed options
+    :param setup_logging: ``True`` if setup logging handlers, ``False`` to use handlers already registered
     :return: the session object of the creation (its structure for now is experimental and might change on short notice)
     """
-    session = session_via_cli(args, options)
-    with session:
-        session.run()
-    return session
+    of_session = session_via_cli(args, options, setup_logging)
+    with of_session:
+        of_session.run()
+    return of_session
+
 
+def session_via_cli(args, options=None, setup_logging=True):
+    """
+    Create a virtualenv session (same as cli_run, but this does not perform the creation). Use this if you just want to
+    query what the virtual environment would look like, but not actually create it.
 
-# noinspection PyProtectedMember
-def session_via_cli(args, options=None):
-    parser, elements = build_parser(args, options)
+    :param args: the command line arguments
+    :param options: passing in a ``VirtualEnvOptions`` object allows return of the parsed options
+    :param setup_logging: ``True`` if setup logging handlers, ``False`` to use handlers already registered
+    :return: the session object of the creation (its structure for now is experimental and might change on short notice)
+    """
+    parser, elements = build_parser(args, options, setup_logging)
     options = parser.parse_args(args)
     creator, seeder, activators = tuple(e.create(options) for e in elements)  # create types
-    session = Session(options.verbosity, options.app_data, parser._interpreter, creator, seeder, activators)
-    return session
+    of_session = Session(options.verbosity, options.app_data, parser._interpreter, creator, seeder, activators)  # noqa
+    return of_session
 
 
-# noinspection PyProtectedMember
-def build_parser(args=None, options=None):
+def build_parser(args=None, options=None, setup_logging=True):
     parser = VirtualEnvConfigParser(options)
     add_version_flag(parser)
     parser.add_argument(
@@ -47,7 +56,7 @@ def build_parser(args=None, options=None):
         default=False,
         help="on failure also display the stacktrace internals of virtualenv",
     )
-    _do_report_setup(parser, args)
+    _do_report_setup(parser, args, setup_logging)
     options = load_app_data(args, parser, options)
     handle_extra_commands(options)
 
@@ -121,7 +130,7 @@ def add_version_flag(parser):
     )
 
 
-def _do_report_setup(parser, args):
+def _do_report_setup(parser, args, setup_logging):
     level_map = ", ".join("{}={}".format(logging.getLevelName(l), c) for c, l in sorted(list(LEVELS.items())))
     msg = "verbosity = verbose - quiet, default {}, mapping => {}"
     verbosity_group = parser.add_argument_group(
@@ -131,4 +140,11 @@ def _do_report_setup(parser, args):
     verbosity.add_argument("-v", "--verbose", action="count", dest="verbose", help="increase verbosity", default=2)
     verbosity.add_argument("-q", "--quiet", action="count", dest="quiet", help="decrease verbosity", default=0)
     option, _ = parser.parse_known_args(args)
-    setup_report(option.verbosity)
+    if setup_logging:
+        setup_report(option.verbosity)
+
+
+__all__ = (
+    "cli_run",
+    "session_via_cli",
+)

tests/conftest.py

@@ -196,8 +196,8 @@ def coverage_env(monkeypatch, link, request):
         # we inject right after creation, we cannot collect coverage on site.py - used for helper scripts, such as debug
         from virtualenv import run
 
-        def via_cli(args, options):
-            session = prev_run(args, options)
+        def _session_via_cli(args, options, setup_logging):
+            session = prev_run(args, options, setup_logging)
             old_run = session.creator.run
 
             def create_run():
@@ -211,7 +211,7 @@ def create_run():
 
         obj = {"cov": None}
         prev_run = run.session_via_cli
-        monkeypatch.setattr(run, "session_via_cli", via_cli)
+        monkeypatch.setattr(run, "session_via_cli", _session_via_cli)
 
         def finish():
             cov = obj["cov"]

tests/unit/config/test___main__.py

@@ -24,8 +24,8 @@ def _func(exception):
 
         prev_session = session_via_cli
 
-        def _session_via_cli(args, options=None):
-            prev_session(args, options)
+        def _session_via_cli(args, options=None, setup_logging=True):
+            prev_session(args, options, setup_logging)
             raise exception
 
         mocker.patch("virtualenv.run.session_via_cli", side_effect=_session_via_cli)

tests/unit/create/test_creator.py

@@ -250,8 +250,8 @@ def test_venv_fails_not_inline(tmp_path, capsys, mocker):
         if os.geteuid() == 0:
             pytest.skip("no way to check permission restriction when running under root")
 
-    def _session_via_cli(args, options=None):
-        session = session_via_cli(args, options)
+    def _session_via_cli(args, options=None, setup_logging=True):
+        session = session_via_cli(args, options, setup_logging)
         assert session.creator.can_be_inline is False
         return session
 

tests/unit/test_run.py

@@ -1,10 +1,12 @@
 from __future__ import absolute_import, unicode_literals
 
+import logging
+
 import pytest
 import six
 
 from virtualenv import __version__
-from virtualenv.run import cli_run
+from virtualenv.run import cli_run, session_via_cli
 
 
 def test_help(capsys):
@@ -31,3 +33,14 @@ def test_version(capsys):
     import virtualenv
 
     assert virtualenv.__file__ in content
+
+
+@pytest.mark.parametrize("on", [True, False])
+def test_logging_setup(caplog, on):
+    caplog.set_level(logging.DEBUG)
+    session_via_cli(["env"], setup_logging=on)
+    # DEBUG only level output is generated during this phase, default output is WARN, so if on no records should be
+    if on:
+        assert not caplog.records
+    else:
+        assert caplog.records