Deprecate --print-deps-only in favor of --print-deps-to-file=-

README.rst

@@ -14,11 +14,11 @@ The ``tox-current-env`` plugin adds two options:
    An attempt to run this with a Python version that doesn't match will fail
    (if ``tox`` is invoked from an Python 3.7 environment, any non 3.7 testenv will fail).
 
-``tox --print-deps-only`` / ``--print-deps-to-file``
+``tox --print-deps-to=FILE``
     Instead of running any ``commands``,
-    simply prints the declared dependencies in ``deps`` to the standard output or specified file.
+    simply prints the declared dependencies in ``deps`` to the specified ``FILE``.
     This is useful for preparing the current environment for the above.
-    ``--print-deps-to-file`` will overwrite the file if it already exists.
+    Use ``-`` for ``FILE`` to print to standard output.
 
 Invoking ``tox`` without any of the above options should behave as regular ``tox`` invocation without this plugin.
 Any deviation from this behavior is considered a bug.
@@ -82,7 +82,7 @@ and ``pip``-installing locally:
 Usage
 -----
 
-When the plugin is installed, use ``tox`` with ``--current-env`` or ``--print-deps-only`` and all the other options as usual. Assuming your ``tox`` is installed on Python 3.7:
+When the plugin is installed, use ``tox`` with ``--current-env`` or ``--print-deps-to`` and all the other options as usual. Assuming your ``tox`` is installed on Python 3.7:
 
 .. code-block:: console
 
@@ -114,7 +114,7 @@ To get list of test dependencies, run:
 
 .. code-block:: console
 
-   $ tox -e py37 --print-deps-only
+   $ tox -e py37 --print-deps-to -
    py37 create: /home/pythonista/projects/holy-grail/tests/.tox/py37
    py37 installed: ...you can see almost anything here...
    py37 run-test-pre: PYTHONHASHSEED='3333333333'
@@ -159,7 +159,7 @@ Don't mix current-env and regular tox runs
 
 Tox caches the virtualenvs it creates, and doesn't distinguish between
 regular virtualenvs and ``--current-env``.
-Don't mix ``tox --current-env`` or ``tox --print-deps-only`` runs
+Don't mix ``tox --current-env`` or ``tox --print-deps-to`` runs
 and regular ``tox`` runs (without the flag).
 If you ever need to do this, use tox's ``--recreate/-r`` flag to clear the cache.
 
@@ -183,7 +183,7 @@ Read `the documentation for passing environment variables to tox
 Other limitations and known bugs
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The ``installed:`` line in the output of ``tox --print-deps-only`` shows irrelevant output
+The ``installed:`` line in the output of ``tox --print-deps-to`` shows irrelevant output
 (based on the content of the real or faked virtual environment).
 
 Regardless of any `Python flags <https://docs.python.org/3/using/cmdline.html>`_ used in the shebang of ``tox``,

src/tox_current_env/hooks.py

@@ -3,6 +3,8 @@ import shutil
 import subprocess
 import sys
 import tox
+import warnings
+import argparse
 
 try:
     import importlib.metadata as importlib_metadata
@@ -24,30 +26,37 @@ def tox_addoption(parser):
         action="store_true",
         dest="print_deps_only",
         default=False,
-        help="Don't run tests, only print the dependencies to stdout",
+        help="Deprecated, equivalent to `--print-deps-to -`",
     )
     parser.add_argument(
+        "--print-deps-to",
         "--print-deps-to-file",
         action="store",
-        dest="print_deps_path",
+        dest="print_deps_to",
-        metavar="PATH",
+        type=argparse.FileType('w'),
+        metavar="FILE",
         default=None,
-        help="Like --print-deps-only, but to a file. Overwrites the file if it exists.",
+        help="Don't run tests, only print the dependencies to the given file "
+            + "(use `-` for stdout)",
     )
 
 
 @tox.hookimpl
 def tox_configure(config):
     """Stores options in the config. Makes all commands external and skips sdist"""
-    if config.option.print_deps_only and config.option.print_deps_path:
+    if config.option.print_deps_only:
-        raise tox.exception.ConfigError(
+        warnings.warn(
-            "--print-deps-only cannot be used together with --print-deps-to-file"
+            "--print-deps-only is deprecated; use `--print-deps-to -`",
+            DeprecationWarning,
         )
-    if config.option.print_deps_path is not None:
+        if not config.option.print_deps_to:
-        config.option.print_deps_only = True
+            config.option.print_deps_to = sys.stdout
-        with open(config.option.print_deps_path, "w", encoding="utf-8") as f:
+        else:
-            f.write("")
+            raise tox.exception.ConfigError(
-    if config.option.current_env or config.option.print_deps_only:
+                "--print-deps-only cannot be used together "
+                + "with --print-deps-to"
+            )
+    if config.option.current_env or config.option.print_deps_to:
         config.skipsdist = True
         for testenv in config.envconfigs:
             config.envconfigs[testenv].whitelist_externals = "*"
@@ -89,16 +98,16 @@ def rm_venv(venv):
 def unsupported_raise(config, venv):
     if config.option.recreate:
         return
-    regular = not (config.option.current_env or config.option.print_deps_only)
+    regular = not (config.option.current_env or config.option.print_deps_to)
     if regular and is_current_env_link(venv):
         if hasattr(tox.hookspecs, "tox_cleanup"):
             raise tox.exception.ConfigError(
-                "Looks like previous --current-env or --print-deps-only tox run didn't finish the cleanup. "
+                "Looks like previous --current-env or --print-deps-to tox run didn't finish the cleanup. "
                 "Run tox run with --recreate (-r) or manually remove the environment in .tox."
             )
         else:
             raise tox.exception.ConfigError(
-                "Regular tox run after --current-env or --print-deps-only tox run is not supported without --recreate (-r)."
+                "Regular tox run after --current-env or --print-deps-to tox run is not supported without --recreate (-r)."
             )
     elif config.option.current_env and is_proper_venv(venv):
         raise tox.exception.ConfigError(
@@ -111,7 +120,7 @@ def tox_testenv_create(venv, action):
     """We create a fake virtualenv with just the symbolic link"""
     config = venv.envconfig.config
     create_fake_env = check_version = config.option.current_env
-    if config.option.print_deps_only:
+    if config.option.print_deps_to:
         if is_any_env(venv):
             # We don't need anything
             return True
@@ -122,7 +131,7 @@ def tox_testenv_create(venv, action):
             # because it's cheaper, faster and won't install stuff
             create_fake_env = True
     if check_version:
-        # With real --current-env, we check this, but not with --print-deps-only only
+        # With real --current-env, we check this, but not with --print-deps-to only
         version_info = venv.envconfig.python_info.version_info
         if version_info is None:
             raise tox.exception.InterpreterNotFound(venv.envconfig.basepython)
@@ -164,21 +173,21 @@ def tox_testenv_install_deps(venv, action):
     """We don't install anything"""
     config = venv.envconfig.config
     unsupported_raise(config, venv)
-    if config.option.current_env or config.option.print_deps_only:
+    if config.option.current_env or config.option.print_deps_to:
         return True
 
 
 @tox.hookimpl
 def tox_runtest(venv, redirect):
-    """If --print-deps-only, prints deps instead of running tests"""
+    """If --print-deps-to, prints deps instead of running tests"""
     config = venv.envconfig.config
     unsupported_raise(config, venv)
-    if config.option.print_deps_path is not None:
+    if config.option.print_deps_to:
-        with open(config.option.print_deps_path, "a", encoding="utf-8") as f:
+        print(
-            print(*venv.get_resolved_dependencies(), sep="\n", file=f)
+            *venv.get_resolved_dependencies(),
-        return True
+            sep="\n",
-    if config.option.print_deps_only:
+            file=config.option.print_deps_to,
-        print(*venv.get_resolved_dependencies(), sep="\n")
+        )
         return True
 
 

tests/test_integration.py

@@ -6,6 +6,7 @@ import shutil
 import subprocess
 import sys
 import textwrap
+import warnings
 
 from packaging import version
 
@@ -29,6 +30,12 @@ def projdir(tmp_path, monkeypatch):
     monkeypatch.chdir(pwd)
 
 
+@pytest.fixture(params=('--print-deps-only', '--print-deps-to-file=-', '--print-deps-to=-'))
+def print_deps_stdout_arg(request):
+    """Argument for printing deps to stdout"""
+    return request.param
+
+
 def tox(*args, quiet=True, **kwargs):
     kwargs.setdefault("encoding", "utf-8")
     kwargs.setdefault("stdout", subprocess.PIPE)
@@ -95,8 +102,8 @@ def test_all_toxenv_current_env_skip_missing():
 
 
 @pytest.mark.parametrize("toxenv", ["py36", "py37", "py38", "py39"])
-def test_print_deps_only(toxenv):
+def test_print_deps(toxenv, print_deps_stdout_arg):
-    result = tox("-e", toxenv, "--print-deps-only")
+    result = tox("-e", toxenv, print_deps_stdout_arg)
     expected = textwrap.dedent(
         f"""
         six
@@ -109,8 +116,21 @@ def test_print_deps_only(toxenv):
     assert result.stdout == expected
 
 
-def test_allenvs_print_deps_only():
+@pytest.mark.parametrize("toxenv", ["py36", "py37", "py38", "py39"])
-    result = tox("--print-deps-only")
+def test_print_deps_only_deprecated(toxenv):
+    result = tox(
+        "-e", toxenv, '--print-deps-only',
+        env={**os.environ, 'PYTHONWARNINGS': 'always'},
+    )
+    waring_text = (
+        "DeprecationWarning: --print-deps-only is deprecated; "
+        + "use `--print-deps-to -`"
+    )
+    assert waring_text in result.stderr
+
+
+def test_allenvs_print_deps(print_deps_stdout_arg):
+    result = tox(print_deps_stdout_arg)
     expected = textwrap.dedent(
         """
         six
@@ -229,7 +249,7 @@ def test_regular_after_current_is_supported():
     assert "--recreate" not in result.stderr
 
 
-def test_regular_after_killed_current_is_not_supported():
+def test_regular_after_killed_current_is_not_supported(print_deps_stdout_arg):
     # fake broken tox run
     shutil.rmtree(DOT_TOX, ignore_errors=True)
     (DOT_TOX / NATIVE_TOXENV / "bin").mkdir(parents=True)
@@ -240,8 +260,8 @@ def test_regular_after_killed_current_is_not_supported():
     assert "--recreate" in result.stderr
 
 
-def test_regular_after_first_deps_only_is_supported():
+def test_regular_after_first_print_deps_is_supported(print_deps_stdout_arg):
-    result = tox("-e", NATIVE_TOXENV, "--print-deps-only")
+    result = tox("-e", NATIVE_TOXENV, print_deps_stdout_arg)
     assert result.stdout.splitlines()[0] == "six"
     result = tox("-e", NATIVE_TOXENV)
     lines = sorted(result.stdout.splitlines()[:1])
@@ -283,18 +303,18 @@ def test_current_recreate_after_regular():
     assert result.stdout.splitlines()[0] == NATIVE_EXEC_PREFIX_MSG
 
 
-def test_current_after_deps_only():
+def test_current_after_print_deps(print_deps_stdout_arg):
     # this is quite fast, so we can do it several times
     for _ in range(3):
-        result = tox("-e", NATIVE_TOXENV, "--print-deps-only")
+        result = tox("-e", NATIVE_TOXENV, print_deps_stdout_arg)
         assert "bin/python" not in result.stdout
         assert "six" in result.stdout
         result = tox("-re", NATIVE_TOXENV, "--current-env")
         assert result.stdout.splitlines()[0] == NATIVE_EXEC_PREFIX_MSG
 
 
-def test_regular_recreate_after_deps_only():
+def test_regular_recreate_after_print_deps(print_deps_stdout_arg):
-    result = tox("-e", NATIVE_TOXENV, "--print-deps-only")
+    result = tox("-e", NATIVE_TOXENV, print_deps_stdout_arg)
     assert "bin/python" not in result.stdout
     assert "six" in result.stdout
 
@@ -304,12 +324,12 @@ def test_regular_recreate_after_deps_only():
     assert sitelib.is_dir()
     assert len(list(sitelib.glob("test-*.dist-info"))) == 1
 
-    result = tox("-e", NATIVE_TOXENV, "--print-deps-only")
+    result = tox("-e", NATIVE_TOXENV, print_deps_stdout_arg)
     assert "bin/python" not in result.stdout
     assert "six" in result.stdout
 
 
-def test_print_deps_without_python_command(tmp_path):
+def test_print_deps_without_python_command(tmp_path, print_deps_stdout_arg):
     bin = tmp_path / "bin"
     bin.mkdir()
     tox_link = bin / "tox"
@@ -317,7 +337,7 @@ def test_print_deps_without_python_command(tmp_path):
     tox_link.symlink_to(tox_path)
     env = {**os.environ, "PATH": str(bin)}
 
-    result = tox("-e", NATIVE_TOXENV, "--print-deps-only", env=env)
+    result = tox("-e", NATIVE_TOXENV, print_deps_stdout_arg, env=env)
     expected = textwrap.dedent(
         f"""
         six