Change default version command - Enhancement #263 #264

NilayGanvit · 2026-01-31T12:31:28Z

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python-cla-bot · 2026-01-31T12:31:32Z

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Copilot

Pull request overview

Adds a new py default subcommand to show or set the default Python runtime, persisting the selection via a .default marker file and reflecting it in install discovery.

Changes:

Introduces DefaultCommand and its implementation in default_command.py
Updates install discovery to read .default and mark the matching install as default
Adds initial tests for the new command and ignores /.venv/

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 13 comments.

Show a summary per file

File	Description
tests/test_default_command.py	Adds tests targeting `DefaultCommand` behavior (currently light on assertions).
src/manage/installs.py	Reads `<install_dir>/.default` and marks the matching install as `default=True`.
src/manage/default_command.py	Implements the `default` command logic (show current / set new default).
src/manage/commands.py	Registers the `default` command, CLI schema hooks, and usage/help text updates.
.gitignore	Ignores a root `/.venv/` directory.

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Copilot · 2026-01-31T12:40:24Z

src/manage/commands.py

+     (f"{EXE_NAME} default !B!<TAG>!W!\n",
+     "Set the default Python version to use when no specific version is " +
+     "requested. Use without !B!<TAG>!W! to show the current default."),


The new PYMANAGER_USAGE_DOCS entry for default will make help output list the default command twice (once from PYMANAGER_USAGE_DOCS and again from the per-command loop in BaseCommand.show_usage() that appends all COMMANDS). Consider removing this tuple from PYMANAGER_USAGE_DOCS and relying on the standard USAGE_LINE/HELP_LINE registration, or update show_usage() to de-duplicate entries.

Suggested change

(f"{EXE_NAME} default !B!<TAG>!W!\n",

"Set the default Python version to use when no specific version is " +

"requested. Use without !B!<TAG>!W! to show the current default."),

Copilot · 2026-01-31T12:40:24Z

src/manage/default_command.py

+def _load_default_install_id(install_dir):
+    """Load the saved default install ID from the marker file."""
+    try:
+        default_file = _get_default_config_file(install_dir)
+        if default_file.exists():


_load_default_install_id() is currently unused. Either remove it, or use it in _show_current_default() so the command can report the saved default ID even when it isn’t present in the current installs list.

Copilot · 2026-01-31T12:40:24Z

src/manage/default_command.py

+        default_file = _get_default_config_file(install_dir)
+        default_file.parent.mkdir(parents=True, exist_ok=True)
+        default_file.write_text(install_id, encoding="utf-8")
+        LOGGER.info("Default Python version set to: !G!%s!W!", install_id)


This logs a “Default … set” message, and _set_default_version() logs another one after calling _save_default_install_id(). Consider keeping a single user-facing log line to avoid duplicate console output.

Suggested change

LOGGER.info("Default Python version set to: !G!%s!W!", install_id)

LOGGER.debug("Saved default install ID: %s", install_id)

Copilot · 2026-01-31T12:40:25Z

src/manage/installs.py

+    # Check for a saved default install marker
+    try:
+        default_file = Path(install_dir) / ".default"
+        if default_file.exists():
+            default_id = default_file.read_text(encoding="utf-8").strip()


The new .default marker behavior introduced here isn’t covered by tests. Please add a test (e.g., using patched_installs + tmp_path) that writes an install ID into <install_dir>/.default and asserts get_installs() marks the matching install with default=True (and that it affects get_install_to_run(..., tag='default') as intended).

Copilot · 2026-01-31T12:40:25Z

src/manage/default_command.py

+    if not matching:
+        raise NoInstallFoundError(tag=tag)
+
+    selected_install, selected_run_for = matching[0]


selected_run_for is assigned but never used. Rename it to _ (or otherwise use it) to avoid unused-variable warnings and make intent clearer.

Suggested change

selected_install, selected_run_for = matching[0]

selected_install = matching[0][0]

Copilot · 2026-01-31T12:40:26Z

src/manage/default_command.py

+    except NoInstallsError:
+        LOGGER.info("No Python installations found.")
+        return
+


_show_current_default() expects cmd.get_installs() to raise NoInstallsError, but BaseCommand.get_installs() returns an empty list when there are no installs. As written, the no-installs case will print “No explicit default set” instead of “No Python installations found.” Handle if not installs: explicitly (and consider removing the unreachable except NoInstallsError:).

Suggested change

if not installs:

LOGGER.info("No Python installations found.")

return

Copilot · 2026-01-31T12:40:26Z

src/manage/default_command.py

+    else:
+        # Set new default
+        tag = " ".join(cmd.args[0:1])  # Take the first argument as the tag
+        _set_default_version(cmd, tag)


_set_default_version() may raise NoInstallFoundError, but execute() doesn’t handle it. Since manage.main() treats uncaught exceptions as INTERNAL ERROR, py default <TAG> on an unknown tag will look like a crash. Catch NoInstallFoundError here (log a user-facing message and raise SystemExit(1), or convert to ArgumentError) to match other commands’ error-handling patterns.

Suggested change

_set_default_version(cmd, tag)

try:

_set_default_version(cmd, tag)

except NoInstallFoundError:

LOGGER.error("No Python installation found matching tag '%s'.", tag)

raise ArgumentError(f"No Python installation found matching tag '{tag}'.") from None

Copilot · 2026-01-31T12:40:26Z

src/manage/default_command.py

+import json
+from pathlib import Path as PathlibPath
+
+from .exceptions import ArgumentError, NoInstallsError, NoInstallFoundError
+from .installs import get_installs, get_matching_install_tags


Unused imports: json, PathlibPath, and get_installs are not used in this module. Please remove them to keep the module minimal and avoid lint/static-analysis warnings.

Suggested change

import json

from pathlib import Path as PathlibPath

from .exceptions import ArgumentError, NoInstallsError, NoInstallFoundError

from .installs import get_installs, get_matching_install_tags

from .exceptions import ArgumentError, NoInstallsError, NoInstallFoundError

from .installs import get_matching_install_tags

Copilot · 2026-01-31T12:40:26Z

tests/test_default_command.py

+def test_default_command_no_args_no_installs(assert_log):
+    """Test default command with no arguments and no installations."""
+    cmd = commands.DefaultCommand([commands.DefaultCommand.CMD], None)
+    # This should handle the case gracefully
+    # We expect it to either show a message about no installs or show current default


This test is non-deterministic and doesn’t assert behavior. DefaultCommand(..., root=None) may read installs from the real environment (sys.prefix/pkgs), and the test passes even if execute() produces incorrect output. Use tmp_path/monkeypatch (e.g., patched_installs) and assert on output/state so the test validates the no-installs behavior.

Copilot · 2026-01-31T12:40:26Z

tests/test_default_command.py

@@ -0,0 +1,59 @@
+"""Tests for the default command."""
+
+import pytest


Import of 'pytest' is not used.

Suggested change

import pytest

Change default version command - Enhancement python#263

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Change default version command - Enhancement #263 #264

Change default version command - Enhancement #263 #264

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	(f"{EXE_NAME} default !B!<TAG>!W!\n",
	"Set the default Python version to use when no specific version is " +
	"requested. Use without !B!<TAG>!W! to show the current default."),

	LOGGER.info("Default Python version set to: !G!%s!W!", install_id)
	LOGGER.debug("Saved default install ID: %s", install_id)

	selected_install, selected_run_for = matching[0]
	selected_install = matching[0][0]

-        _set_default_version(cmd, tag)
+        try:
+            _set_default_version(cmd, tag)
+        except NoInstallFoundError:
+            LOGGER.error("No Python installation found matching tag '%s'.", tag)
+            raise ArgumentError(f"No Python installation found matching tag '{tag}'.") from None

		@@ -0,0 +1,59 @@
		"""Tests for the default command."""

		import pytest

Change default version command - Enhancement #263 #264

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Change default version command - Enhancement #263 #264

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