Force UTF-8 when reading subprocess output

Subprocess execution was ensuring that Python in the
subprocess used UTF-8 encoding for its standard streams,
but it wasn't ensuring that the *current* process also
did so when communicating with the subprocess via pipes.

Closes #42

src/venvstacks/_util.py

@@ -84,12 +84,18 @@ def run_python_command_unchecked(
     env: Mapping[str, str] | None = None,
     **kwds: Any,
 ) -> subprocess.CompletedProcess[str]:
+    # Ensure required env vars are passed down on Windows,
+    # and run Python in isolated mode with UTF-8 as the text encoding
     run_env = os.environ.copy()
     if env is not None:
         run_env.update(env)
     run_env.update(_SUBPROCESS_PYTHON_CONFIG)
+    # Default to running in text mode,
+    # but allow it to be explicitly switched off
+    text = kwds.pop("text", True)
+    encoding = "utf-8" if text else None
     result: subprocess.CompletedProcess[str] = subprocess.run(
-        command, env=env, text=True, **kwds
+        command, env=env, text=text, encoding=encoding, **kwds
     )
     return result
 

tests/support.py

@@ -3,13 +3,16 @@
 import json
 import os
 import subprocess
+import sys
 import tomllib
 
 from dataclasses import dataclass, fields
 from pathlib import Path
 from typing import Any, cast, Mapping
 from unittest.mock import create_autospec
 
+import pytest
+
 from venvstacks._util import run_python_command
 from venvstacks.stacks import (
     BuildEnvironment,
@@ -20,6 +23,21 @@
 
 _THIS_DIR = Path(__file__).parent
 
+##################################
+# Marking test cases
+##################################
+
+# Basic marking uses the pytest.mark API directly
+# See pyproject.toml and tests/README.md for the defined marks
+
+def requires_venv(description: str) -> pytest.MarkDecorator:
+    """Skip test case when running tests outside a virtual environment"""
+    return pytest.mark.skipif(
+        sys.prefix == sys.base_prefix,
+        reason=f"{description} requires test execution in venv",
+    )
+
+
 ##################################
 # Exporting test artifacts
 ##################################

tests/test_cli_invocation.py

@@ -22,6 +22,7 @@
 from venvstacks.stacks import BuildEnvironment, EnvironmentLock, IndexConfig
 from venvstacks._util import run_python_command_unchecked
 
+from support import requires_venv
 
 def report_traceback(exc: BaseException | None) -> str:
     if exc is None:
@@ -148,26 +149,41 @@ def test_implicit_help(self, mocked_runner: MockedRunner) -> None:
         assert result.exception is None, report_traceback(result.exception)
         assert result.exit_code == 0
 
-    # See https://github.com/lmstudio-ai/venvstacks/issues/42
-    @pytest.mark.xfail(
-        sys.platform == "win32", reason="UnicodeDecodeError parsing output"
-    )
+    @requires_venv("Entry point test")
+    def test_entry_point_help_raw(self) -> None:
+        expected_entry_point = Path(sys.executable).parent / "venvstacks"
+        command = [str(expected_entry_point), "--help"]
+        result = run_python_command_unchecked(
+            command, text=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE
+        )
+        if result.stdout is not None:
+            # Usage message should suggest direct execution
+            assert b"Usage: venvstacks [" in result.stdout
+            # Top-level callback docstring is used as the overall CLI help text
+            cli_help = cli.handle_app_options.__doc__
+            assert cli_help is not None
+            assert cli_help.strip().encode() in result.stdout
+        # Check operation result last to ensure test results are as informative as possible
+        assert result.returncode == 0
+        assert result.stdout is not None
+
+    @requires_venv("Entry point test")
     def test_entry_point_help(self) -> None:
-        if sys.prefix == sys.base_prefix:
-            pytest.skip("Entry point test requires test execution in venv")
         expected_entry_point = Path(sys.executable).parent / "venvstacks"
         command = [str(expected_entry_point), "--help"]
         result = run_python_command_unchecked(
             command, stdout=subprocess.PIPE, stderr=subprocess.PIPE
         )
-        # Usage message should suggest direct execution
-        assert "Usage: venvstacks [" in result.stdout
-        # Top-level callback docstring is used as the overall CLI help text
-        cli_help = cli.handle_app_options.__doc__
-        assert cli_help is not None
-        assert cli_help.strip() in result.stdout
+        if result.stdout is not None:
+            # Usage message should suggest direct execution
+            assert "Usage: venvstacks [" in result.stdout
+            # Top-level callback docstring is used as the overall CLI help text
+            cli_help = cli.handle_app_options.__doc__
+            assert cli_help is not None
+            assert cli_help.strip() in result.stdout
         # Check operation result last to ensure test results are as informative as possible
         assert result.returncode == 0
+        assert result.stdout is not None
 
 
 EXPECTED_USAGE_PREFIX = "Usage: python -m venvstacks "