fix: better error printouts

pyproject.toml

@@ -39,6 +39,9 @@ filterwarnings = [
 ]
 
 [tool.mypy]
+files = "src"
+python_version = "3.6"
+warn_unused_configs = true
 strict = true
 
 [[tool.mypy.overrides]]

setup.cfg

@@ -63,7 +63,7 @@ test =
     setuptools>=56.0.0;python_version >= "3.10"
 typing =
     importlib-metadata>=4.6.4
-    mypy==0.910
+    mypy==0.931
     typing-extensions>=3.7.4.3
 virtualenv =
     virtualenv>=20.0.35

src/build/__init__.py

@@ -12,6 +12,7 @@
 import re
 import subprocess
 import sys
+import textwrap
 import types
 import warnings
 import zipfile
@@ -85,8 +86,8 @@ def __init__(
         self, exception: Exception, description: Optional[str] = None, exc_info: _ExcInfoType = (None, None, None)
     ) -> None:
         super().__init__()
-        self.exception: Exception = exception
-        self.exc_info: _ExcInfoType = exc_info
+        self.exception = exception
+        self.exc_info = exc_info
         self._description = description
 
     def __str__(self) -> str:
@@ -104,6 +105,27 @@ def __str__(self) -> str:
         return f'Failed to validate `build-system` in pyproject.toml: {self.args[0]}'
 
 
+class FailedProcessError(Exception):
+    """
+    Exception raised when an setup or prepration operation fails.
+    """
+
+    def __init__(self, exception: subprocess.CalledProcessError, description: str) -> None:
+        super().__init__()
+        self.exception = exception
+        self._description = description
+
+    def __str__(self) -> str:
+        cmd = ' '.join(self.exception.cmd)
+        description = f"{self._description}\n  Command '{cmd}' failed with return code {self.exception.returncode}"
+        for stream_name in ('stdout', 'stderr'):
+            stream = getattr(self.exception, stream_name)
+            if stream:
+                description += f'\n  {stream_name}:\n'
+                description += textwrap.indent(stream.decode(), '    ')
+        return description
+
+
 class TypoWarning(Warning):
     """
     Warning raised when a potential typo is found
@@ -481,11 +503,12 @@ def log(message: str) -> None:
 
 __all__ = (
     '__version__',
+    'BuildBackendException',
+    'BuildException',
     'ConfigSettingsType',
+    'FailedProcessError',
+    'ProjectBuilder',
     'RunnerType',
-    'BuildException',
-    'BuildBackendException',
     'TypoWarning',
     'check_dependency',
-    'ProjectBuilder',
 )

src/build/__main__.py

@@ -13,11 +13,11 @@
 import traceback
 import warnings
 
-from typing import Dict, Iterable, Iterator, List, Optional, Sequence, TextIO, Type, Union
+from typing import Dict, Iterator, List, NoReturn, Optional, Sequence, TextIO, Type, Union
 
 import build
 
-from build import BuildBackendException, BuildException, ConfigSettingsType, PathType, ProjectBuilder
+from build import BuildBackendException, BuildException, ConfigSettingsType, FailedProcessError, PathType, ProjectBuilder
 from build.env import IsolatedEnvBuilder
 
 
@@ -71,7 +71,7 @@ def _setup_cli() -> None:
         colorama.init()  # fix colors on windows
 
 
-def _error(msg: str, code: int = 1) -> None:  # pragma: no cover
+def _error(msg: str, code: int = 1) -> NoReturn:  # pragma: no cover
     """
     Print an error message and exit. Will color the output when writing to a TTY.
 
@@ -146,23 +146,24 @@ def _build(
 def _handle_build_error() -> Iterator[None]:
     try:
         yield
-    except BuildException as e:
+    except (BuildException, FailedProcessError) as e:
         _error(str(e))
     except BuildBackendException as e:
         if isinstance(e.exception, subprocess.CalledProcessError):
             print()
+            _error(str(e))
+
+        if e.exc_info:
+            tb_lines = traceback.format_exception(
+                e.exc_info[0],
+                e.exc_info[1],
+                e.exc_info[2],
+                limit=-1,
+            )
+            tb = ''.join(tb_lines)
         else:
-            if e.exc_info:
-                tb_lines = traceback.format_exception(
-                    e.exc_info[0],
-                    e.exc_info[1],
-                    e.exc_info[2],
-                    limit=-1,
-                )
-                tb = ''.join(tb_lines)
-            else:
-                tb = traceback.format_exc(-1)
-            print('\n{dim}{}{reset}\n'.format(tb.strip('\n'), **_STYLES))
+            tb = traceback.format_exc(-1)
+        print('\n{dim}{}{reset}\n'.format(tb.strip('\n'), **_STYLES))
         _error(str(e))
 
 
@@ -250,9 +251,6 @@ def main_parser() -> argparse.ArgumentParser:
     """
     Construct the main parser.
     """
-    # mypy does not recognize module.__path__
-    # https://github.com/python/mypy/issues/1422
-    paths: Iterable[str] = build.__path__  # type: ignore
     parser = argparse.ArgumentParser(
         description=textwrap.indent(
             textwrap.dedent(
@@ -285,7 +283,7 @@ def main_parser() -> argparse.ArgumentParser:
         '--version',
         '-V',
         action='version',
-        version=f"build {build.__version__} ({','.join(paths)})",
+        version=f"build {build.__version__} ({','.join(build.__path__)})",
     )
     parser.add_argument(
         '--sdist',

src/build/env.py

@@ -74,7 +74,7 @@ def _should_use_virtualenv() -> bool:
 def _subprocess(cmd: List[str]) -> None:
     """Invoke subprocess and output stdout and stderr if it fails."""
     try:
-        subprocess.check_output(cmd, stderr=subprocess.STDOUT)
+        subprocess.run(cmd, check=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
     except subprocess.CalledProcessError as e:
         print(e.output.decode(), end='', file=sys.stderr)
         raise e
@@ -219,7 +219,7 @@ def install(self, requirements: Iterable[str]) -> None:
 
 def _create_isolated_env_virtualenv(path: str) -> Tuple[str, str]:
     """
-    On Python 2 we use the virtualenv package to provision a virtual environment.
+    We optionally can use the virtualenv package to provision a virtual environment.
 
     :param path: The path where to create the isolated build environment
     :return: The Python executable and script folder
@@ -235,7 +235,7 @@ def _create_isolated_env_virtualenv(path: str) -> Tuple[str, str]:
 def _fs_supports_symlink() -> bool:
     """Return True if symlinks are supported"""
     # Using definition used by venv.main()
-    if os.name != 'nt':
+    if not sys.platform.startswith('win'):
         return True
 
     # Windows may support symlinks (setting in Windows 10)
@@ -260,7 +260,12 @@ def _create_isolated_env_venv(path: str) -> Tuple[str, str]:
 
     import packaging.version
 
-    venv.EnvBuilder(with_pip=True, symlinks=_fs_supports_symlink()).create(path)
+    simlinks = _fs_supports_symlink()
+    try:
+        venv.EnvBuilder(with_pip=True, symlinks=simlinks).create(path)
+    except subprocess.CalledProcessError as exc:
+        raise build.FailedProcessError(exc, 'Failed to create venv. Maybe try installing virtualenv.') from None
+
     executable, script_dir, purelib = _find_executable_and_scripts(path)
 
     # Get the version of pip in the environment
@@ -304,7 +309,7 @@ def _find_executable_and_scripts(path: str) -> Tuple[str, str, str]:
         paths = sysconfig.get_paths(scheme='posix_prefix', vars=config_vars)
     else:
         paths = sysconfig.get_paths(vars=config_vars)
-    executable = os.path.join(paths['scripts'], 'python.exe' if os.name == 'nt' else 'python')
+    executable = os.path.join(paths['scripts'], 'python.exe' if sys.platform.startswith('win') else 'python')
     if not os.path.exists(executable):
         raise RuntimeError(f'Virtual environment creation failed, executable {executable} missing')
 

tests/conftest.py

@@ -66,7 +66,7 @@ def pytest_addoption(parser):
     parser.addoption('--only-integration', action='store_true', help='only run the integration tests')
 
 
-PYPY3_WIN_VENV_BAD = platform.python_implementation() == 'PyPy' and os.name == 'nt'
+PYPY3_WIN_VENV_BAD = platform.python_implementation() == 'PyPy' and sys.platform.startswith('win')
 PYPY3_WIN_M = 'https://foss.heptapod.net/pypy/pypy/-/issues/3323 and https://foss.heptapod.net/pypy/pypy/-/issues/3321'
 
 

tests/test_env.py

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: MIT
 import collections
+import inspect
 import logging
-import os
 import platform
 import shutil
 import subprocess
@@ -103,8 +103,9 @@ def test_isolated_env_log(mocker, caplog, package_test_flit):
     caplog.set_level(logging.DEBUG)
 
     builder = build.env.IsolatedEnvBuilder()
+    frameinfo = inspect.getframeinfo(inspect.currentframe())
     builder.log('something')  # line number 106
-    with builder as env:  # line number 107
+    with builder as env:
         env.install(['something'])
 
     assert [(record.levelname, record.message) for record in caplog.records] == [
@@ -113,7 +114,7 @@ def test_isolated_env_log(mocker, caplog, package_test_flit):
         ('INFO', 'Installing packages in isolated environment... (something)'),
     ]
     if sys.version_info >= (3, 8):  # stacklevel
-        assert [(record.lineno) for record in caplog.records] == [106, 107, 198]
+        assert [(record.lineno) for record in caplog.records] == [frameinfo.lineno + 1, 107, 198]
 
 
 @pytest.mark.isolated
@@ -151,8 +152,8 @@ def test_pip_needs_upgrade_mac_os_11(mocker, pip_version, arch):
 
 
 @pytest.mark.isolated
-@pytest.mark.skipif(IS_PYPY3 and os.name == 'nt', reason='Isolated tests not supported on PyPy3 + Windows')
-@pytest.mark.parametrize('has_symlink', [True, False] if os.name == 'nt' else [True])
+@pytest.mark.skipif(IS_PYPY3 and sys.platform.startswith('win'), reason='Isolated tests not supported on PyPy3 + Windows')
+@pytest.mark.parametrize('has_symlink', [True, False] if sys.platform.startswith('win') else [True])
 def test_venv_symlink(mocker, has_symlink):
     if has_symlink:
         mocker.patch('os.symlink')

tests/test_integration.py

@@ -16,7 +16,7 @@
 import build.__main__
 
 
-IS_WINDOWS = os.name == 'nt'
+IS_WINDOWS = sys.platform.startswith('win')
 IS_PYPY3 = platform.python_implementation() == 'PyPy'
 
 
@@ -102,7 +102,7 @@ def test_build(monkeypatch, project, args, call, tmp_path):
     monkeypatch.setenv('SETUPTOOLS_SCM_PRETEND_VERSION', '0+dummy')  # for the projects that use setuptools_scm
 
     if call and call[0] == 'pyproject-build':
-        exe_name = f"pyproject-build{'.exe' if os.name == 'nt' else ''}"
+        exe_name = f"pyproject-build{'.exe' if sys.platform.startswith('win') else ''}"
         exe = os.path.join(os.path.dirname(sys.executable), exe_name)
         if os.path.exists(exe):
             call[0] = exe

tests/test_main.py

@@ -5,7 +5,9 @@
 import io
 import os
 import re
+import subprocess
 import sys
+import venv
 
 import pytest
 
@@ -399,3 +401,31 @@ def test_colors_conflict(monkeypatch, main_reload_styles):
             importlib.reload(build.__main__)
 
         assert build.__main__._STYLES == build.__main__._NO_COLORS
+
+
+def raise_called_process_err(*args, **kwargs):
+    raise subprocess.CalledProcessError(1, ['test', 'args'], b'stdoutput', b'stderror')
+
+
+def test_venv_fail(monkeypatch, package_test_flit, tmp_dir, capsys):
+    monkeypatch.setattr(venv.EnvBuilder, 'create', raise_called_process_err)
+    monkeypatch.setenv('NO_COLOR', '')
+
+    with pytest.raises(SystemExit):
+        build.__main__.main([package_test_flit, '-o', tmp_dir])
+
+    stdout, stderr = capsys.readouterr()
+
+    assert (
+        stdout
+        == '''\
+* Creating venv isolated environment...
+ERROR Failed to create venv. Maybe try installing virtualenv.
+  Command 'test args' failed with return code 1
+  stdout:
+    stdoutput
+  stderr:
+    stderror
+'''
+    )
+    assert stderr == ''

tests/test_projectbuilder.py

@@ -173,7 +173,7 @@ def test_init(mocker, package_test_flit, package_legacy, test_no_permission, pac
     )
 
     # PermissionError
-    if os.name != 'nt':  # can't correctly set the permissions required for this
+    if not sys.platform.startswith('win'):  # can't correctly set the permissions required for this
         with pytest.raises(build.BuildException):
             build.ProjectBuilder(test_no_permission)
 

tox.ini

@@ -52,7 +52,7 @@ commands =
 description = run type check on code base
 extras = typing
 commands =
-    mypy --show-error-codes --python-version 3.6 src/build
+    mypy --show-error-codes src/build
 
 [testenv:{py311, py310, py39, py38, py37, py36, pypy3}-min]
 description = check minimum versions required of all dependencies