main: build binary distributions via sdists by default

CHANGELOG.rst

@@ -7,8 +7,18 @@ Unreleased
 ==========
 
 - Add ``ProjectBuilder.metadata_path`` helper (`PR #303`_, Fixes `#301`_)
+- Added a ``build.__main__.build_package_via_sdist`` method (`PR #304`_)
+
+Breaking Changes
+----------------
+
+- Binary distributions are now built via the sdist by default in the CLI (`PR #304`_, Fixes `#257`_)
+  - ``python -m build`` will now build a sdist, extract it, and build a wheel from the source
+- As a side-effect of `PR #304`_, ``build.__main__.build_package`` no longer does CLI error handling (print nice message and exit the program)
 
 .. _PR #303: https://github.com/pypa/build/pull/303
+.. _PR #304: https://github.com/pypa/build/pull/304
+.. _#257: https://github.com/pypa/build/issues/257
 .. _#301: https://github.com/pypa/build/issues/301
 
 

src/build/__main__.py

@@ -3,13 +3,18 @@
 from __future__ import print_function
 
 import argparse
+import contextlib
 import os
+import shutil
 import subprocess
 import sys
+import tarfile
+import tempfile
+import textwrap
 import traceback
 import warnings
 
-from typing import Iterable, List, Optional, Sequence, TextIO, Type, Union
+from typing import Iterable, Iterator, List, Optional, Sequence, TextIO, Type, Union
 
 import build
 
@@ -28,6 +33,16 @@
 __all__ = ['build', 'main', 'main_parser']
 
 
+if sys.version_info[0] == 2:
+
+    def _indent(text, prefix):  # type: (str, str) -> str
+        return ''.join(prefix + line for line in text.splitlines(True))
+
+
+else:
+    from textwrap import indent as _indent
+
+
 def _showwarning(message, category, filename, lineno, file=None, line=None):  # pragma: no cover
     # type: (Union[Warning, str], Type[Warning], str, int, Optional[TextIO], Optional[str]) -> None
     prefix = 'WARNING'
@@ -57,54 +72,41 @@ def _format_dep_chain(dep_chain):  # type: (Sequence[str]) -> str
     return ' -> '.join(dep.partition(';')[0].strip() for dep in dep_chain)
 
 
-def _build_in_isolated_env(builder, outdir, distributions, config_settings):
-    # type: (ProjectBuilder, str, List[str], ConfigSettingsType) -> None
-    for distribution in distributions:
-        with IsolatedEnvBuilder() as env:
-            builder.python_executable = env.executable
-            builder.scripts_dir = env.scripts_dir
-            # first install the build dependencies
-            env.install(builder.build_system_requires)
-            # then get the extra required dependencies from the backend (which was installed in the call above :P)
-            env.install(builder.get_requires_for_build(distribution))
-            builder.build(distribution, outdir, config_settings)
-
-
-def _build_in_current_env(builder, outdir, distributions, config_settings, skip_dependency_check=False):
-    # type: (ProjectBuilder, str, List[str], ConfigSettingsType, bool) -> None
-    for dist in distributions:
-        if not skip_dependency_check:
-            missing = builder.check_dependencies(dist)
-            if missing:
-                _error(
-                    'Missing dependencies:'
-                    + ''.join('\n\t' + dep for deps in missing for dep in (deps[0], _format_dep_chain(deps[1:])) if dep)
-                )
+def _build_in_isolated_env(builder, outdir, distribution, config_settings):
+    # type: (ProjectBuilder, str, str, Optional[ConfigSettingsType]) -> str
+    with IsolatedEnvBuilder() as env:
+        builder.python_executable = env.executable
+        builder.scripts_dir = env.scripts_dir
+        # first install the build dependencies
+        env.install(builder.build_system_requires)
+        # then get the extra required dependencies from the backend (which was installed in the call above :P)
+        env.install(builder.get_requires_for_build(distribution))
+        return builder.build(distribution, outdir, config_settings or {})
 
-        builder.build(dist, outdir, config_settings)
 
+def _build_in_current_env(builder, outdir, distribution, config_settings, skip_dependency_check=False):
+    # type: (ProjectBuilder, str, str, Optional[ConfigSettingsType], bool) -> str
+    if not skip_dependency_check:
+        missing = builder.check_dependencies(distribution)
+        if missing:
+            dependencies = ''.join('\n\t' + dep for deps in missing for dep in (deps[0], _format_dep_chain(deps[1:])) if dep)
+            _error('Missing dependencies:{}'.format(dependencies))
 
-def build_package(srcdir, outdir, distributions, config_settings=None, isolation=True, skip_dependency_check=False):
-    # type: (str, str, List[str], Optional[ConfigSettingsType], bool, bool) -> None
-    """
-    Run the build process.
+    return builder.build(distribution, outdir, config_settings or {})
 
-    :param srcdir: Source directory
-    :param outdir: Output directory
-    :param distributions: Distributions to build (sdist and/or wheel)
-    :param config_settings: Configuration settings to be passed to the backend
-    :param isolation: Isolate the build in a separate environment
-    :param skip_dependency_check: Do not perform the dependency check
-    """
-    if not config_settings:
-        config_settings = {}
 
+def _build(isolation, builder, outdir, distribution, config_settings, skip_dependency_check):
+    # type: (bool, ProjectBuilder, str, str, Optional[ConfigSettingsType], bool) -> str
+    if isolation:
+        return _build_in_isolated_env(builder, outdir, distribution, config_settings)
+    else:
+        return _build_in_current_env(builder, outdir, distribution, config_settings, skip_dependency_check)
+
+
+@contextlib.contextmanager
+def _handle_build_error():  # type: () -> Iterator[None]
     try:
-        builder = ProjectBuilder(srcdir)
-        if isolation:
-            _build_in_isolated_env(builder, outdir, distributions, config_settings)
-        else:
-            _build_in_current_env(builder, outdir, distributions, config_settings, skip_dependency_check)
+        yield
     except BuildException as e:
         _error(str(e))
     except BuildBackendException as e:
@@ -126,14 +128,82 @@ def build_package(srcdir, outdir, distributions, config_settings=None, isolation
         _error(str(e))
 
 
+def build_package(srcdir, outdir, distributions, config_settings=None, isolation=True, skip_dependency_check=False):
+    # type: (str, str, List[str], Optional[ConfigSettingsType], bool, bool) -> None
+    """
+    Run the build process.
+
+    :param srcdir: Source directory
+    :param outdir: Output directory
+    :param distribution: Distribution to build (sdist or wheel)
+    :param config_settings: Configuration settings to be passed to the backend
+    :param isolation: Isolate the build in a separate environment
+    :param skip_dependency_check: Do not perform the dependency check
+    """
+    builder = ProjectBuilder(srcdir)
+    for distribution in distributions:
+        _build(isolation, builder, outdir, distribution, config_settings, skip_dependency_check)
+
+
+def build_package_via_sdist(srcdir, outdir, distributions, config_settings=None, isolation=True, skip_dependency_check=False):
+    # type: (str, str, List[str], Optional[ConfigSettingsType], bool, bool) -> None
+    """
+    Build a sdist and then the specified distributions from it.
+
+    :param srcdir: Source directory
+    :param outdir: Output directory
+    :param distribution: Distribution to build (only wheel)
+    :param config_settings: Configuration settings to be passed to the backend
+    :param isolation: Isolate the build in a separate environment
+    :param skip_dependency_check: Do not perform the dependency check
+    """
+    if 'sdist' in distributions:
+        raise ValueError('Only binary distributions are allowed but sdist was specified')
+
+    builder = ProjectBuilder(srcdir)
+    sdist = _build(isolation, builder, outdir, 'sdist', config_settings, skip_dependency_check)
+
+    # extract sdist
+    sdist_name = os.path.basename(sdist)
+    sdist_out = tempfile.mkdtemp(dir=outdir, prefix='build-via-sdist-')
+    with tarfile.open(sdist) as t:
+        t.extractall(sdist_out)
+        builder = ProjectBuilder(os.path.join(sdist_out, sdist_name[: -len('.tar.gz')]))
+        for distribution in distributions:
+            _build(isolation, builder, outdir, distribution, config_settings, skip_dependency_check)
+
+    # remove sdist source if there was no exception
+    shutil.rmtree(sdist_out, ignore_errors=True)
+
+
 def main_parser():  # type: () -> argparse.ArgumentParser
     """
     Construct the main parser.
     """
     # mypy does not recognize module.__path__
     # https://github.com/python/mypy/issues/1422
     paths = build.__path__  # type: Iterable[Optional[str]]  # type: ignore
-    parser = argparse.ArgumentParser()
+    parser = argparse.ArgumentParser(
+        description=_indent(  # textwrap.indent
+            textwrap.dedent(
+                '''
+                A simple, correct PEP 517 package builder.
+
+                By default, a source distribution (sdist) is built from {srcdir}
+                and a binary distribution (wheel) is built from the sdist.
+                This is recommended as it will ensure the sdist can be used
+                to build wheels.
+
+                Pass -s/--sdist and/or -w/--wheel to build a specific distribution.
+                If you do this, the default behavior will be disabled, and all
+                artifacts will be built from {srcdir} (even if you combine
+                -w/--wheel with -s/--sdist, the wheel will be built from {srcdir}).
+                '''
+            ).strip(),
+            '    ',
+        ),
+        formatter_class=argparse.RawTextHelpFormatter,
+    )
     parser.add_argument(
         'srcdir',
         type=str,
@@ -151,13 +221,13 @@ def main_parser():  # type: () -> argparse.ArgumentParser
         '--sdist',
         '-s',
         action='store_true',
-        help='build a source distribution (enabled by default if no target is specified)',
+        help='build a source distribution (disables the default behavior)',
     )
     parser.add_argument(
         '--wheel',
         '-w',
         action='store_true',
-        help='build a wheel (enabled by default if no target is specified)',
+        help='build a wheel (disables the default behavior)',
     )
     parser.add_argument(
         '--outdir',
@@ -187,7 +257,7 @@ def main_parser():  # type: () -> argparse.ArgumentParser
     return parser
 
 
-def main(cli_args, prog=None):  # type: (List[str], Optional[str]) -> None
+def main(cli_args, prog=None):  # type: (List[str], Optional[str]) -> None  # noqa: C901
     """
     Parse the CLI arguments and invoke the build process.
 
@@ -218,14 +288,20 @@ def main(cli_args, prog=None):  # type: (List[str], Optional[str]) -> None
     if args.wheel:
         distributions.append('wheel')
 
-    # default targets
-    if not distributions:
-        distributions = ['sdist', 'wheel']
-
     # outdir is relative to srcdir only if omitted.
     outdir = os.path.join(args.srcdir, 'dist') if args.outdir is None else args.outdir
 
-    build_package(args.srcdir, outdir, distributions, config_settings, not args.no_isolation, args.skip_dependency_check)
+    if distributions:
+        build_call = build_package
+    else:
+        build_call = build_package_via_sdist
+        distributions = ['wheel']
+    try:
+        with _handle_build_error():
+            build_call(args.srcdir, outdir, distributions, config_settings, not args.no_isolation, args.skip_dependency_check)
+    except Exception as e:  # pragma: no cover
+        print(traceback.format_exc())
+        _error(str(e))
 
 
 def entrypoint():  # type: () -> None

tests/conftest.py

@@ -170,6 +170,11 @@ def test_bad_wheel_path(packages_path):
     return os.path.join(packages_path, 'test-bad-wheel')
 
 
+@pytest.fixture
+def test_cant_build_via_sdist_path(packages_path):
+    return os.path.join(packages_path, 'test-cant-build-via-sdist')
+
+
 @pytest.fixture
 def test_no_permission(packages_path):
     path = os.path.join(packages_path, 'test-no-permission')

tests/packages/test-cant-build-via-sdist/backend_bad_sdist.py

@@ -0,0 +1,23 @@
+# SPDX-License-Identifier: MIT
+
+import os.path
+import tarfile
+import zipfile
+
+
+def build_sdist(sdist_directory, config_settings=None):
+    name = 'test_cant_build_via_sdist-1.0.0'
+    file = '{}.tar.gz'.format(name)
+    with tarfile.open(os.path.join(sdist_directory, file), 'w') as t:
+        t.add('pyproject.toml', '{}/pyproject.toml'.format(name))
+        t.add('backend_bad_sdist.py', '{}/backend_bad_sdist.py'.format(name))
+    return file
+
+
+def build_wheel(wheel_directory, config_settings=None, metadata_directory=None):
+    if not os.path.isfile('some-file-that-is-needed-for-build.txt'):
+        raise FileNotFoundError('some-file-that-is-needed-for-build.txt is missing!')
+    # pragma: no cover
+    file = 'test_cant_build_via_sdist-1.0.0-py2.py3-none-any.whl'
+    zipfile.ZipFile(os.path.join(wheel_directory, file), 'w').close()
+    return file

tests/packages/test-cant-build-via-sdist/pyproject.toml

@@ -0,0 +1,4 @@
+[build-system]
+build-backend = 'backend_bad_sdist'
+backend-path = ['.']
+requires = []

tests/packages/test-setuptools/setup.cfg

@@ -1,3 +1,6 @@
 [metadata]
 name = test_setuptools
 version = 1.0.0
+
+[bdist_wheel]
+universal = 1

tests/test_integration.py

@@ -2,6 +2,7 @@
 
 import os
 import os.path
+import platform
 import re
 import shutil
 import subprocess
@@ -20,6 +21,11 @@
 import build.__main__
 
 
+IS_WINDOWS = os.name == 'nt'
+IS_PYPY3 = sys.version_info[0] == 3 and platform.python_implementation() == 'PyPy'
+IS_PY35 = sys.version_info[:2] == (3, 5)
+
+
 INTEGRATION_SOURCES = {
     'dateutil': ('dateutil/dateutil', '2.8.1'),
     'pip': ('pypa/pip', '20.2.1'),
@@ -101,6 +107,8 @@ def _ignore_folder(base, filenames):
 def test_build(monkeypatch, project, args, call, tmp_path):
     if project == 'flit' and '--no-isolation' in args:
         pytest.xfail("can't build flit without isolation due to missing dependencies")
+    if project == 'Solaar' and IS_WINDOWS and (IS_PYPY3 or IS_PY35):
+        pytest.xfail('Solaar fails building wheels via sdists on Windows in Python 3.5 or PyPy 3')
 
     monkeypatch.chdir(tmp_path)
     monkeypatch.setenv('SETUPTOOLS_SCM_PRETEND_VERSION', 'dummy')  # for the projects that use setuptools_scm