From 3492e4ad16507cfb23f70b9ad65bfac06bffd7a9 Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: Sun, 14 Jun 2020 22:31:03 +0100
Subject: [PATCH 01/10] Pull out high-level interfaces as an extended example

---
 README.rst                                    | 48 ++++----------
 buildtool_demo/__init__.py                    |  0
 {pep517 => buildtool_demo}/build.py           | 46 +-------------
 {pep517 => buildtool_demo}/check.py           |  0
 {pep517 => buildtool_demo}/colorlog.py        |  0
 {pep517 => buildtool_demo}/dirtools.py        |  0
 {pep517 => buildtool_demo}/envbuild.py        | 37 ++++++++++-
 {pep517 => buildtool_demo}/meta.py            |  4 +-
 buildtool_demo/tests/__init__.py              |  0
 .../tests/samples/buildsys_pkgs/buildsys.py   | 62 +++++++++++++++++++
 .../samples/buildsys_pkgs/buildsys_minimal.py | 34 ++++++++++
 .../samples/pkg1/pkg1-0.5.dist-info/LICENSE   | 21 +++++++
 .../samples/pkg1/pkg1-0.5.dist-info/METADATA  |  9 +++
 .../samples/pkg1/pkg1-0.5.dist-info/RECORD    |  5 ++
 .../samples/pkg1/pkg1-0.5.dist-info/WHEEL     |  5 ++
 buildtool_demo/tests/samples/pkg1/pkg1.py     |  3 +
 .../tests/samples/pkg1/pyproject.toml         |  3 +
 .../tests}/test_envbuild.py                   |  2 +-
 {tests => buildtool_demo/tests}/test_meta.py  |  2 +-
 pep517/__init__.py                            |  2 +
 pep517/pyproject.py                           | 52 ++++++++++++++++
 pep517/wrappers.py                            | 47 ++++----------
 pyproject.toml                                |  2 -
 tests/test_build.py                           | 27 --------
 tests/test_hook_fallbacks.py                  |  2 +-
 tests/test_inplace_hooks.py                   |  2 +-
 tests/test_pyproject.py                       | 27 ++++++++
 27 files changed, 289 insertions(+), 153 deletions(-)
 create mode 100644 buildtool_demo/__init__.py
 rename {pep517 => buildtool_demo}/build.py (62%)
 rename {pep517 => buildtool_demo}/check.py (100%)
 rename {pep517 => buildtool_demo}/colorlog.py (100%)
 rename {pep517 => buildtool_demo}/dirtools.py (100%)
 rename {pep517 => buildtool_demo}/envbuild.py (87%)
 rename {pep517 => buildtool_demo}/meta.py (94%)
 create mode 100644 buildtool_demo/tests/__init__.py
 create mode 100644 buildtool_demo/tests/samples/buildsys_pkgs/buildsys.py
 create mode 100644 buildtool_demo/tests/samples/buildsys_pkgs/buildsys_minimal.py
 create mode 100644 buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/LICENSE
 create mode 100644 buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/METADATA
 create mode 100644 buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/RECORD
 create mode 100644 buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/WHEEL
 create mode 100644 buildtool_demo/tests/samples/pkg1/pkg1.py
 create mode 100644 buildtool_demo/tests/samples/pkg1/pyproject.toml
 rename {tests => buildtool_demo/tests}/test_envbuild.py (95%)
 rename {tests => buildtool_demo/tests}/test_meta.py (97%)
 create mode 100644 pep517/pyproject.py
 delete mode 100644 tests/test_build.py
 create mode 100644 tests/test_pyproject.py

diff --git a/README.rst b/README.rst
index b5ebb3b..8582c29 100644
--- a/README.rst
+++ b/README.rst
@@ -8,38 +8,21 @@ provides:
   the current process.
 - Fallbacks for the optional hooks, so that frontends can call the hooks without
   checking which are defined.
-- Higher-level functions which install the build dependencies into a
-  temporary environment and build a wheel/sdist using them.
+- Functions to load the build system table from ``pyproject.toml``, with
+  optional fallback to setuptools.
 
 Run the tests with ``pytest`` or `tox <https://pypi.org/project/tox>`_.
 
-High level usage, with build requirements handled:
+Usage:
 
 .. code-block:: python
 
     import os
-    from pep517.envbuild import build_wheel, build_sdist
+    from pep517 import Pep517HookCaller
+    from pep517.pyproject import load_system
 
     src = 'path/to/source'  # Folder containing 'pyproject.toml'
-    destination = 'also/a/folder'
-    whl_filename = build_wheel(src, destination)
-    assert os.path.isfile(os.path.join(destination, whl_filename))
-
-    targz_filename = build_sdist(src, destination)
-    assert os.path.isfile(os.path.join(destination, targz_filename))
-
-Lower level usage—you are responsible for ensuring build requirements are
-available:
-
-.. code-block:: python
-
-    import os
-    import toml
-    from pep517.wrappers import Pep517HookCaller
-
-    src = 'path/to/source'  # Folder containing 'pyproject.toml'
-    with open(os.path.join(src, 'pyproject.toml')) as f:
-        build_sys = toml.load(f)['build-system']
+    build_sys = load_system(src)
 
     print(build_sys['requires'])  # List of static requirements
 
@@ -57,18 +40,9 @@ available:
     whl_filename = hooks.build_wheel(destination, config_options)
     assert os.path.isfile(os.path.join(destination, whl_filename))
 
-To test the build backend for a project, run in a system shell:
-
-.. code-block:: shell
-
-    python3 -m pep517.check path/to/source  # source dir containing pyproject.toml
-
-To build a backend into source and/or binary distributions, run in a shell:
-
-.. code-block:: shell
-
-    python -m pep517.build path/to/source  # source dir containing pyproject.toml
+The caller is responsible for installing build dependencies.
+The static requirements should be installed before trying to call any hooks.
 
-This 'build' module should be considered experimental while the PyPA `decides
-on the best place for this functionality
-<https://github.com/pypa/packaging-problems/issues/219>`_.
+The ``buildtool_demo`` package in this repository gives a more complete
+example of how to use the hooks. This is an example, and doesn't get installed
+with the ``pep517`` package.
diff --git a/buildtool_demo/__init__.py b/buildtool_demo/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/pep517/build.py b/buildtool_demo/build.py
similarity index 62%
rename from pep517/build.py
rename to buildtool_demo/build.py
index 7618c78..f24a332 100644
--- a/pep517/build.py
+++ b/buildtool_demo/build.py
@@ -3,58 +3,16 @@
 import argparse
 import logging
 import os
-import toml
 import shutil
 
 from .envbuild import BuildEnvironment
-from .wrappers import Pep517HookCaller
+from pep517 import Pep517HookCaller
+from pep517.pyproject import load_system, validate_system
 from .dirtools import tempdir, mkdir_p
-from .compat import FileNotFoundError
 
 log = logging.getLogger(__name__)
 
 
-def validate_system(system):
-    """
-    Ensure build system has the requisite fields.
-    """
-    required = {'requires', 'build-backend'}
-    if not (required <= set(system)):
-        message = "Missing required fields: {missing}".format(
-            missing=required-set(system),
-        )
-        raise ValueError(message)
-
-
-def load_system(source_dir):
-    """
-    Load the build system from a source dir (pyproject.toml).
-    """
-    pyproject = os.path.join(source_dir, 'pyproject.toml')
-    with open(pyproject) as f:
-        pyproject_data = toml.load(f)
-    return pyproject_data['build-system']
-
-
-def compat_system(source_dir):
-    """
-    Given a source dir, attempt to get a build system backend
-    and requirements from pyproject.toml. Fallback to
-    setuptools but only if the file was not found or a build
-    system was not indicated.
-    """
-    try:
-        system = load_system(source_dir)
-    except (FileNotFoundError, KeyError):
-        system = {}
-    system.setdefault(
-        'build-backend',
-        'setuptools.build_meta:__legacy__',
-    )
-    system.setdefault('requires', ['setuptools', 'wheel'])
-    return system
-
-
 def _do_build(hooks, env, dist, dest):
     get_requires_name = 'get_requires_for_build_{dist}'.format(**locals())
     get_requires = getattr(hooks, get_requires_name)
diff --git a/pep517/check.py b/buildtool_demo/check.py
similarity index 100%
rename from pep517/check.py
rename to buildtool_demo/check.py
diff --git a/pep517/colorlog.py b/buildtool_demo/colorlog.py
similarity index 100%
rename from pep517/colorlog.py
rename to buildtool_demo/colorlog.py
diff --git a/pep517/dirtools.py b/buildtool_demo/dirtools.py
similarity index 100%
rename from pep517/dirtools.py
rename to buildtool_demo/dirtools.py
diff --git a/pep517/envbuild.py b/buildtool_demo/envbuild.py
similarity index 87%
rename from pep517/envbuild.py
rename to buildtool_demo/envbuild.py
index cacd2b1..4dd1536 100644
--- a/pep517/envbuild.py
+++ b/buildtool_demo/envbuild.py
@@ -9,8 +9,9 @@
 import sys
 from sysconfig import get_paths
 from tempfile import mkdtemp
+import threading
 
-from .wrappers import Pep517HookCaller, LoggerWrapper
+from pep517 import Pep517HookCaller
 
 log = logging.getLogger(__name__)
 
@@ -26,6 +27,40 @@ def _load_pyproject(source_dir):
     )
 
 
+class LoggerWrapper(threading.Thread):
+    """
+    Read messages from a pipe and redirect them
+    to a logger (see python's logging module).
+    """
+
+    def __init__(self, logger, level):
+        threading.Thread.__init__(self)
+        self.daemon = True
+
+        self.logger = logger
+        self.level = level
+
+        # create the pipe and reader
+        self.fd_read, self.fd_write = os.pipe()
+        self.reader = os.fdopen(self.fd_read)
+
+        self.start()
+
+    def fileno(self):
+        return self.fd_write
+
+    @staticmethod
+    def remove_newline(msg):
+        return msg[:-1] if msg.endswith(os.linesep) else msg
+
+    def run(self):
+        for line in self.reader:
+            self._write(self.remove_newline(line))
+
+    def _write(self, message):
+        self.logger.log(self.level, message)
+
+
 class BuildEnvironment(object):
     """Context manager to install build deps in a simple temporary environment
 
diff --git a/pep517/meta.py b/buildtool_demo/meta.py
similarity index 94%
rename from pep517/meta.py
rename to buildtool_demo/meta.py
index d525de5..1704c42 100644
--- a/pep517/meta.py
+++ b/buildtool_demo/meta.py
@@ -17,9 +17,9 @@
     from zipp import Path
 
 from .envbuild import BuildEnvironment
-from .wrappers import Pep517HookCaller, quiet_subprocess_runner
+from pep517 import Pep517HookCaller, quiet_subprocess_runner
+from pep517.pyproject import validate_system, load_system, compat_system
 from .dirtools import tempdir, mkdir_p, dir_to_zipfile
-from .build import validate_system, load_system, compat_system
 
 log = logging.getLogger(__name__)
 
diff --git a/buildtool_demo/tests/__init__.py b/buildtool_demo/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/buildtool_demo/tests/samples/buildsys_pkgs/buildsys.py b/buildtool_demo/tests/samples/buildsys_pkgs/buildsys.py
new file mode 100644
index 0000000..e1750c1
--- /dev/null
+++ b/buildtool_demo/tests/samples/buildsys_pkgs/buildsys.py
@@ -0,0 +1,62 @@
+"""This is a very stupid backend for testing purposes.
+
+Don't use this for any real code.
+"""
+
+from glob import glob
+from os.path import join as pjoin
+import shutil
+import tarfile
+from zipfile import ZipFile
+
+
+def get_requires_for_build_wheel(config_settings):
+    return ['wheelwright']
+
+
+def prepare_metadata_for_build_wheel(metadata_directory, config_settings):
+    for distinfo in glob('*.dist-info'):
+        shutil.copytree(distinfo, pjoin(metadata_directory, distinfo))
+
+
+def prepare_build_wheel_files(build_directory, config_settings):
+    shutil.copy('pyproject.toml', build_directory)
+    for pyfile in glob('*.py'):
+        shutil.copy(pyfile, build_directory)
+    for distinfo in glob('*.dist-info'):
+        shutil.copytree(distinfo, pjoin(build_directory, distinfo))
+
+
+def build_wheel(wheel_directory, config_settings, metadata_directory=None):
+    whl_file = 'pkg1-0.5-py2.py3-none-any.whl'
+    with ZipFile(pjoin(wheel_directory, whl_file), 'w') as zf:
+        for pyfile in glob('*.py'):
+            zf.write(pyfile)
+        for metadata in glob('*.dist-info/*'):
+            zf.write(metadata)
+    return whl_file
+
+
+def get_requires_for_build_sdist(config_settings):
+    return ['frog']
+
+
+class UnsupportedOperation(Exception):
+    pass
+
+
+def build_sdist(sdist_directory, config_settings):
+    if config_settings.get('test_unsupported', False):
+        raise UnsupportedOperation
+
+    target = 'pkg1-0.5.tar.gz'
+    with tarfile.open(pjoin(sdist_directory, target), 'w:gz',
+                      format=tarfile.PAX_FORMAT) as tf:
+        def _add(relpath):
+            tf.add(relpath, arcname='pkg1-0.5/' + relpath)
+
+        _add('pyproject.toml')
+        for pyfile in glob('*.py'):
+            _add(pyfile)
+
+    return target
diff --git a/buildtool_demo/tests/samples/buildsys_pkgs/buildsys_minimal.py b/buildtool_demo/tests/samples/buildsys_pkgs/buildsys_minimal.py
new file mode 100644
index 0000000..6a286b1
--- /dev/null
+++ b/buildtool_demo/tests/samples/buildsys_pkgs/buildsys_minimal.py
@@ -0,0 +1,34 @@
+"""Test backend defining only the mandatory hooks.
+
+Don't use this for any real code.
+"""
+from glob import glob
+from os.path import join as pjoin
+import tarfile
+from zipfile import ZipFile
+
+
+def build_wheel(wheel_directory, config_settings, metadata_directory=None):
+    whl_file = 'pkg2-0.5-py2.py3-none-any.whl'
+    with ZipFile(pjoin(wheel_directory, whl_file), 'w') as zf:
+        for pyfile in glob('*.py'):
+            zf.write(pyfile)
+        for metadata in glob('*.dist-info/*'):
+            zf.write(metadata)
+    return whl_file
+
+
+def build_sdist(sdist_directory, config_settings):
+    target = 'pkg2-0.5.tar.gz'
+    with tarfile.open(pjoin(sdist_directory, target), 'w:gz',
+                      format=tarfile.PAX_FORMAT) as tf:
+        def _add(relpath):
+            tf.add(relpath, arcname='pkg2-0.5/' + relpath)
+
+        _add('pyproject.toml')
+        for pyfile in glob('*.py'):
+            _add(pyfile)
+        for distinfo in glob('*.dist-info'):
+            _add(distinfo)
+
+    return target
diff --git a/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/LICENSE b/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/LICENSE
new file mode 100644
index 0000000..b0ae9db
--- /dev/null
+++ b/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/LICENSE
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2017 Thomas Kluyver
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/METADATA b/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/METADATA
new file mode 100644
index 0000000..7bf2758
--- /dev/null
+++ b/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/METADATA
@@ -0,0 +1,9 @@
+Metadata-Version: 1.2
+Name: pkg1
+Version: 0.5
+Summary: Sample package for tests
+Home-page: https://github.com/takluyver/pep517
+License: UNKNOWN
+Author: Thomas Kluyver
+Author-email: thomas@kluyver.me.uk
+Classifier: License :: OSI Approved :: MIT License
diff --git a/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/RECORD b/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/RECORD
new file mode 100644
index 0000000..74e8cbf
--- /dev/null
+++ b/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/RECORD
@@ -0,0 +1,5 @@
+pkg1.py,sha256=ZawKBtrxtdGEheOCWvwzGZsO8Q1OSzEzecGNsRz-ekc,52
+pkg1-0.5.dist-info/LICENSE,sha256=GyKwSbUmfW38I6Z79KhNjsBLn9-xpR02DkK0NCyLQVQ,1081
+pkg1-0.5.dist-info/WHEEL,sha256=jxKvNaDKHDacpaLi69-vnLKkBSynwBzmMS82pipt1T0,100
+pkg1-0.5.dist-info/METADATA,sha256=GDliGDwDPM11hoO79KhjyJuFgcm-TOj30gewsPNjkHw,251
+pkg1-0.5.dist-info/RECORD,,
diff --git a/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/WHEEL b/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/WHEEL
new file mode 100644
index 0000000..1612133
--- /dev/null
+++ b/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/WHEEL
@@ -0,0 +1,5 @@
+Wheel-Version: 1.0
+Generator: buildsys 0.1
+Root-Is-Purelib: true
+Tag: py2-none-any
+Tag: py3-none-any
diff --git a/buildtool_demo/tests/samples/pkg1/pkg1.py b/buildtool_demo/tests/samples/pkg1/pkg1.py
new file mode 100644
index 0000000..b76d0a9
--- /dev/null
+++ b/buildtool_demo/tests/samples/pkg1/pkg1.py
@@ -0,0 +1,3 @@
+"""Sample package for tests"""
+
+__version__ = '0.5'
diff --git a/buildtool_demo/tests/samples/pkg1/pyproject.toml b/buildtool_demo/tests/samples/pkg1/pyproject.toml
new file mode 100644
index 0000000..95ff87f
--- /dev/null
+++ b/buildtool_demo/tests/samples/pkg1/pyproject.toml
@@ -0,0 +1,3 @@
+[build-system]
+requires = ["eg_buildsys"]
+build-backend = "buildsys"
diff --git a/tests/test_envbuild.py b/buildtool_demo/tests/test_envbuild.py
similarity index 95%
rename from tests/test_envbuild.py
rename to buildtool_demo/tests/test_envbuild.py
index 79c094b..12fbb82 100644
--- a/tests/test_envbuild.py
+++ b/buildtool_demo/tests/test_envbuild.py
@@ -8,7 +8,7 @@
     from mock import patch, call  # Python 2 fallback
 import zipfile
 
-from pep517.envbuild import build_sdist, build_wheel, BuildEnvironment
+from ..envbuild import build_sdist, build_wheel, BuildEnvironment
 
 SAMPLES_DIR = pjoin(dirname(abspath(__file__)), 'samples')
 BUILDSYS_PKGS = pjoin(SAMPLES_DIR, 'buildsys_pkgs')
diff --git a/tests/test_meta.py b/buildtool_demo/tests/test_meta.py
similarity index 97%
rename from tests/test_meta.py
rename to buildtool_demo/tests/test_meta.py
index bd6a2e7..2b024e7 100644
--- a/tests/test_meta.py
+++ b/buildtool_demo/tests/test_meta.py
@@ -4,7 +4,7 @@
 
 import pytest
 
-from pep517 import meta
+from .. import meta
 
 
 pep517_needs_python_3 = pytest.mark.xfail(
diff --git a/pep517/__init__.py b/pep517/__init__.py
index 7355b68..677afd6 100644
--- a/pep517/__init__.py
+++ b/pep517/__init__.py
@@ -2,3 +2,5 @@
 """
 
 __version__ = '0.8.2'
+
+from .wrappers import *  # noqa: F401,F403
diff --git a/pep517/pyproject.py b/pep517/pyproject.py
new file mode 100644
index 0000000..9015a5e
--- /dev/null
+++ b/pep517/pyproject.py
@@ -0,0 +1,52 @@
+import os
+
+import toml
+
+from .compat import FileNotFoundError
+
+__all__ = [
+    'validate_system',
+    'load_system',
+    'compat_system',
+]
+
+
+def validate_system(system):
+    """
+    Ensure build system has the requisite fields.
+    """
+    required = {'requires', 'build-backend'}
+    if not (required <= set(system)):
+        message = "Missing required fields: {missing}".format(
+            missing=required-set(system),
+        )
+        raise ValueError(message)
+
+
+def load_system(source_dir):
+    """
+    Load the build system from a source dir (pyproject.toml).
+    """
+    pyproject = os.path.join(source_dir, 'pyproject.toml')
+    with open(pyproject) as f:
+        pyproject_data = toml.load(f)
+    return pyproject_data['build-system']
+
+
+def compat_system(source_dir):
+    """
+    Given a source dir, attempt to get a build system backend
+    and requirements from pyproject.toml. Fallback to
+    setuptools but only if the file was not found or a build
+    system was not indicated.
+    """
+    try:
+        system = load_system(source_dir)
+    except (FileNotFoundError, KeyError):
+        system = {}
+    system.setdefault(
+        'build-backend',
+        'setuptools.build_meta:__legacy__',
+    )
+    system.setdefault('requires', ['setuptools', 'wheel'])
+    return system
diff --git a/pep517/wrappers.py b/pep517/wrappers.py
index 00a3d1a..85f574b 100644
--- a/pep517/wrappers.py
+++ b/pep517/wrappers.py
@@ -1,4 +1,3 @@
-import threading
 from contextlib import contextmanager
 import os
 from os.path import dirname, abspath, join as pjoin
@@ -9,7 +8,6 @@
 
 from . import compat
 
-
 try:
     import importlib.resources as resources
 
@@ -21,6 +19,17 @@ def _in_proc_script_path():
         yield pjoin(dirname(abspath(__file__)), '_in_process.py')
 
 
+__all__ = [
+    'Pep517HookCaller',
+    'BackendUnavailable',
+    'BackendInvalid',
+    'HookMissing',
+    'UnsupportedOperation',
+    'default_subprocess_runner',
+    'quiet_subprocess_runner',
+]
+
+
 @contextmanager
 def tempdir():
     td = mkdtemp()
@@ -272,37 +281,3 @@ def _call_hook(self, hook_name, kwargs):
             if data.get('hook_missing'):
                 raise HookMissing(hook_name)
             return data['return_val']
-
-
-class LoggerWrapper(threading.Thread):
-    """
-    Read messages from a pipe and redirect them
-    to a logger (see python's logging module).
-    """
-
-    def __init__(self, logger, level):
-        threading.Thread.__init__(self)
-        self.daemon = True
-
-        self.logger = logger
-        self.level = level
-
-        # create the pipe and reader
-        self.fd_read, self.fd_write = os.pipe()
-        self.reader = os.fdopen(self.fd_read)
-
-        self.start()
-
-    def fileno(self):
-        return self.fd_write
-
-    @staticmethod
-    def remove_newline(msg):
-        return msg[:-1] if msg.endswith(os.linesep) else msg
-
-    def run(self):
-        for line in self.reader:
-            self._write(self.remove_newline(line))
-
-    def _write(self, message):
-        self.logger.log(self.level, message)
diff --git a/pyproject.toml b/pyproject.toml
index 65d764c..ce3e4d7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -10,8 +10,6 @@ home-page = "https://github.com/pypa/pep517"
 description-file = "README.rst"
 requires = [
     "toml",
-    "importlib_metadata;python_version<'3.8'",
-    "zipp;python_version<'3.8'",
 ]
 classifiers = [
     "License :: OSI Approved :: MIT License",
diff --git a/tests/test_build.py b/tests/test_build.py
deleted file mode 100644
index 2a7c2bc..0000000
--- a/tests/test_build.py
+++ /dev/null
@@ -1,27 +0,0 @@
-import pytest
-
-from pep517 import build
-
-
-def system(*args):
-    return dict.fromkeys(args)
-
-
-class TestValidateSystem:
-    def test_missing(self):
-        with pytest.raises(ValueError):
-            build.validate_system(system())
-        with pytest.raises(ValueError):
-            build.validate_system(system('requires'))
-        with pytest.raises(ValueError):
-            build.validate_system(system('build-backend'))
-        with pytest.raises(ValueError):
-            build.validate_system(system('other'))
-
-    def test_missing_and_extra(self):
-        with pytest.raises(ValueError):
-            build.validate_system(system('build-backend', 'other'))
-
-    def test_satisfied(self):
-        build.validate_system(system('build-backend', 'requires'))
-        build.validate_system(system('build-backend', 'requires', 'other'))
diff --git a/tests/test_hook_fallbacks.py b/tests/test_hook_fallbacks.py
index c8d4f21..7410de6 100644
--- a/tests/test_hook_fallbacks.py
+++ b/tests/test_hook_fallbacks.py
@@ -4,7 +4,7 @@
 from testpath import modified_env, assert_isfile
 from testpath.tempdir import TemporaryDirectory
 
-from pep517.wrappers import HookMissing, Pep517HookCaller
+from pep517 import HookMissing, Pep517HookCaller
 
 SAMPLES_DIR = pjoin(dirname(abspath(__file__)), 'samples')
 BUILDSYS_PKGS = pjoin(SAMPLES_DIR, 'buildsys_pkgs')
diff --git a/tests/test_inplace_hooks.py b/tests/test_inplace_hooks.py
index 2e6e886..191711c 100644
--- a/tests/test_inplace_hooks.py
+++ b/tests/test_inplace_hooks.py
@@ -3,7 +3,7 @@
 from testpath import modified_env
 import pytest
 
-from pep517.wrappers import Pep517HookCaller, BackendInvalid
+from pep517 import Pep517HookCaller, BackendInvalid
 
 SAMPLES_DIR = pjoin(dirname(abspath(__file__)), 'samples')
 BUILDSYS_PKGS = pjoin(SAMPLES_DIR, 'buildsys_pkgs')
diff --git a/tests/test_pyproject.py b/tests/test_pyproject.py
new file mode 100644
index 0000000..aaca65d
--- /dev/null
+++ b/tests/test_pyproject.py
@@ -0,0 +1,27 @@
+import pytest
+
+from pep517.pyproject import validate_system
+
+
+def system(*args):
+    return dict.fromkeys(args)
+
+
+class TestValidateSystem:
+    def test_missing(self):
+        with pytest.raises(ValueError):
+            validate_system(system())
+        with pytest.raises(ValueError):
+            validate_system(system('requires'))
+        with pytest.raises(ValueError):
+            validate_system(system('build-backend'))
+        with pytest.raises(ValueError):
+            validate_system(system('other'))
+
+    def test_missing_and_extra(self):
+        with pytest.raises(ValueError):
+            validate_system(system('build-backend', 'other'))
+
+    def test_satisfied(self):
+        validate_system(system('build-backend', 'requires'))
+        validate_system(system('build-backend', 'requires', 'other'))

From 92da3870397059264a68cbfd6bd746081aeb7276 Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: Mon, 13 Jul 2020 21:05:08 +0100
Subject: [PATCH 02/10] Move buildtool into examples folder

---
 {buildtool_demo => examples/buildtool}/__init__.py                | 0
 {buildtool_demo => examples/buildtool}/build.py                   | 0
 {buildtool_demo => examples/buildtool}/check.py                   | 0
 {buildtool_demo => examples/buildtool}/colorlog.py                | 0
 {buildtool_demo => examples/buildtool}/dirtools.py                | 0
 {buildtool_demo => examples/buildtool}/envbuild.py                | 0
 {buildtool_demo => examples/buildtool}/meta.py                    | 0
 {buildtool_demo => examples/buildtool}/tests/__init__.py          | 0
 .../buildtool}/tests/samples/buildsys_pkgs/buildsys.py            | 0
 .../buildtool}/tests/samples/buildsys_pkgs/buildsys_minimal.py    | 0
 .../buildtool}/tests/samples/pkg1/pkg1-0.5.dist-info/LICENSE      | 0
 .../buildtool}/tests/samples/pkg1/pkg1-0.5.dist-info/METADATA     | 0
 .../buildtool}/tests/samples/pkg1/pkg1-0.5.dist-info/RECORD       | 0
 .../buildtool}/tests/samples/pkg1/pkg1-0.5.dist-info/WHEEL        | 0
 {buildtool_demo => examples/buildtool}/tests/samples/pkg1/pkg1.py | 0
 .../buildtool}/tests/samples/pkg1/pyproject.toml                  | 0
 {buildtool_demo => examples/buildtool}/tests/test_envbuild.py     | 0
 {buildtool_demo => examples/buildtool}/tests/test_meta.py         | 0
 18 files changed, 0 insertions(+), 0 deletions(-)
 rename {buildtool_demo => examples/buildtool}/__init__.py (100%)
 rename {buildtool_demo => examples/buildtool}/build.py (100%)
 rename {buildtool_demo => examples/buildtool}/check.py (100%)
 rename {buildtool_demo => examples/buildtool}/colorlog.py (100%)
 rename {buildtool_demo => examples/buildtool}/dirtools.py (100%)
 rename {buildtool_demo => examples/buildtool}/envbuild.py (100%)
 rename {buildtool_demo => examples/buildtool}/meta.py (100%)
 rename {buildtool_demo => examples/buildtool}/tests/__init__.py (100%)
 rename {buildtool_demo => examples/buildtool}/tests/samples/buildsys_pkgs/buildsys.py (100%)
 rename {buildtool_demo => examples/buildtool}/tests/samples/buildsys_pkgs/buildsys_minimal.py (100%)
 rename {buildtool_demo => examples/buildtool}/tests/samples/pkg1/pkg1-0.5.dist-info/LICENSE (100%)
 rename {buildtool_demo => examples/buildtool}/tests/samples/pkg1/pkg1-0.5.dist-info/METADATA (100%)
 rename {buildtool_demo => examples/buildtool}/tests/samples/pkg1/pkg1-0.5.dist-info/RECORD (100%)
 rename {buildtool_demo => examples/buildtool}/tests/samples/pkg1/pkg1-0.5.dist-info/WHEEL (100%)
 rename {buildtool_demo => examples/buildtool}/tests/samples/pkg1/pkg1.py (100%)
 rename {buildtool_demo => examples/buildtool}/tests/samples/pkg1/pyproject.toml (100%)
 rename {buildtool_demo => examples/buildtool}/tests/test_envbuild.py (100%)
 rename {buildtool_demo => examples/buildtool}/tests/test_meta.py (100%)

diff --git a/buildtool_demo/__init__.py b/examples/buildtool/__init__.py
similarity index 100%
rename from buildtool_demo/__init__.py
rename to examples/buildtool/__init__.py
diff --git a/buildtool_demo/build.py b/examples/buildtool/build.py
similarity index 100%
rename from buildtool_demo/build.py
rename to examples/buildtool/build.py
diff --git a/buildtool_demo/check.py b/examples/buildtool/check.py
similarity index 100%
rename from buildtool_demo/check.py
rename to examples/buildtool/check.py
diff --git a/buildtool_demo/colorlog.py b/examples/buildtool/colorlog.py
similarity index 100%
rename from buildtool_demo/colorlog.py
rename to examples/buildtool/colorlog.py
diff --git a/buildtool_demo/dirtools.py b/examples/buildtool/dirtools.py
similarity index 100%
rename from buildtool_demo/dirtools.py
rename to examples/buildtool/dirtools.py
diff --git a/buildtool_demo/envbuild.py b/examples/buildtool/envbuild.py
similarity index 100%
rename from buildtool_demo/envbuild.py
rename to examples/buildtool/envbuild.py
diff --git a/buildtool_demo/meta.py b/examples/buildtool/meta.py
similarity index 100%
rename from buildtool_demo/meta.py
rename to examples/buildtool/meta.py
diff --git a/buildtool_demo/tests/__init__.py b/examples/buildtool/tests/__init__.py
similarity index 100%
rename from buildtool_demo/tests/__init__.py
rename to examples/buildtool/tests/__init__.py
diff --git a/buildtool_demo/tests/samples/buildsys_pkgs/buildsys.py b/examples/buildtool/tests/samples/buildsys_pkgs/buildsys.py
similarity index 100%
rename from buildtool_demo/tests/samples/buildsys_pkgs/buildsys.py
rename to examples/buildtool/tests/samples/buildsys_pkgs/buildsys.py
diff --git a/buildtool_demo/tests/samples/buildsys_pkgs/buildsys_minimal.py b/examples/buildtool/tests/samples/buildsys_pkgs/buildsys_minimal.py
similarity index 100%
rename from buildtool_demo/tests/samples/buildsys_pkgs/buildsys_minimal.py
rename to examples/buildtool/tests/samples/buildsys_pkgs/buildsys_minimal.py
diff --git a/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/LICENSE b/examples/buildtool/tests/samples/pkg1/pkg1-0.5.dist-info/LICENSE
similarity index 100%
rename from buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/LICENSE
rename to examples/buildtool/tests/samples/pkg1/pkg1-0.5.dist-info/LICENSE
diff --git a/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/METADATA b/examples/buildtool/tests/samples/pkg1/pkg1-0.5.dist-info/METADATA
similarity index 100%
rename from buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/METADATA
rename to examples/buildtool/tests/samples/pkg1/pkg1-0.5.dist-info/METADATA
diff --git a/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/RECORD b/examples/buildtool/tests/samples/pkg1/pkg1-0.5.dist-info/RECORD
similarity index 100%
rename from buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/RECORD
rename to examples/buildtool/tests/samples/pkg1/pkg1-0.5.dist-info/RECORD
diff --git a/buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/WHEEL b/examples/buildtool/tests/samples/pkg1/pkg1-0.5.dist-info/WHEEL
similarity index 100%
rename from buildtool_demo/tests/samples/pkg1/pkg1-0.5.dist-info/WHEEL
rename to examples/buildtool/tests/samples/pkg1/pkg1-0.5.dist-info/WHEEL
diff --git a/buildtool_demo/tests/samples/pkg1/pkg1.py b/examples/buildtool/tests/samples/pkg1/pkg1.py
similarity index 100%
rename from buildtool_demo/tests/samples/pkg1/pkg1.py
rename to examples/buildtool/tests/samples/pkg1/pkg1.py
diff --git a/buildtool_demo/tests/samples/pkg1/pyproject.toml b/examples/buildtool/tests/samples/pkg1/pyproject.toml
similarity index 100%
rename from buildtool_demo/tests/samples/pkg1/pyproject.toml
rename to examples/buildtool/tests/samples/pkg1/pyproject.toml
diff --git a/buildtool_demo/tests/test_envbuild.py b/examples/buildtool/tests/test_envbuild.py
similarity index 100%
rename from buildtool_demo/tests/test_envbuild.py
rename to examples/buildtool/tests/test_envbuild.py
diff --git a/buildtool_demo/tests/test_meta.py b/examples/buildtool/tests/test_meta.py
similarity index 100%
rename from buildtool_demo/tests/test_meta.py
rename to examples/buildtool/tests/test_meta.py

From 6b8b31192c87f478736090fdec0709a0cbe49d45 Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: Mon, 13 Jul 2020 21:07:27 +0100
Subject: [PATCH 03/10] Fix import

---
 examples/buildtool/check.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/examples/buildtool/check.py b/examples/buildtool/check.py
index 9e0c068..14ff988 100644
--- a/examples/buildtool/check.py
+++ b/examples/buildtool/check.py
@@ -14,7 +14,7 @@
 
 from .colorlog import enable_colourful_output
 from .envbuild import BuildEnvironment
-from .wrappers import Pep517HookCaller
+from pep517 import Pep517HookCaller
 
 log = logging.getLogger(__name__)
 

From 87bb9d3f7a144099e71e3303e901ab0387ca192c Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: Mon, 13 Jul 2020 21:13:21 +0100
Subject: [PATCH 04/10] Add README in examples folder

---
 examples/README.rst | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 examples/README.rst

diff --git a/examples/README.rst b/examples/README.rst
new file mode 100644
index 0000000..3b24a48
--- /dev/null
+++ b/examples/README.rst
@@ -0,0 +1,5 @@
+Examples of using the ``pep517`` library.
+
+* ``buildtool`` is about the simplest possible PEP 517 frontend, which can use
+  PEP 517 backends to build packages. It installs build dependencies into a
+  temporary but non-isolated environment using pip.

From 7e2e1449b1fff7d55a4cb231015dc866eacb171a Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: Mon, 13 Jul 2020 21:18:17 +0100
Subject: [PATCH 05/10] Tests need package installed now

---
 tox.ini | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tox.ini b/tox.ini
index 2502fcf..e264324 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,5 @@
 [tox]
 envlist = py27, py34, py35, py36, py37, pypy, pypy3
-skipsdist = true
 
 [testenv]
 deps = -rdev-requirements.txt

From 00072e8d79e9b444ebdeeba2b6f9957bb7167d2c Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: Mon, 13 Jul 2020 21:18:36 +0100
Subject: [PATCH 06/10] Expand flit_core requirement to <4

---
 pyproject.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pyproject.toml b/pyproject.toml
index ce3e4d7..fe7f337 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["flit_core >=2,<3"]
+requires = ["flit_core >=2,<4"]
 build-backend = "flit_core.buildapi"
 
 [tool.flit.metadata]

From 021ed3555da863bcc822590598bde3287a16e41b Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: Mon, 13 Jul 2020 21:20:15 +0100
Subject: [PATCH 07/10] Enable isolated_build for Tox to use PEP 517

---
 tox.ini | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tox.ini b/tox.ini
index e264324..4ffcb74 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,6 @@
 [tox]
 envlist = py27, py34, py35, py36, py37, pypy, pypy3
+isolated_build = True
 
 [testenv]
 deps = -rdev-requirements.txt

From 94c4a87987931704c7dea1fe638ec3d32da3f617 Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: Mon, 13 Jul 2020 21:25:03 +0100
Subject: [PATCH 08/10] Try upgrading virtualenv on Travis

---
 .travis.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.travis.yml b/.travis.yml
index 712a531..3ce9c1e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -31,6 +31,7 @@ jobs:
 cache: pip
 
 install:
+- pip install -U virtualenv
 - pip install tox tox-venv
 
 script: tox

From 512ddb46d0826de13966316082d12cb179c238ad Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: Mon, 13 Jul 2020 21:27:41 +0100
Subject: [PATCH 09/10] Or maybe upgrade pip

---
 .travis.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.travis.yml b/.travis.yml
index 3ce9c1e..44b6b73 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -31,7 +31,7 @@ jobs:
 cache: pip
 
 install:
-- pip install -U virtualenv
+- pip install -U pip
 - pip install tox tox-venv
 
 script: tox

From e70e03e734442817cb7ee41fc8fbdec574a81721 Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: Mon, 13 Jul 2020 21:30:57 +0100
Subject: [PATCH 10/10] Try using virtualenv for tox environments

---
 .travis.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 44b6b73..b91c18a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -31,7 +31,7 @@ jobs:
 cache: pip
 
 install:
-- pip install -U pip
-- pip install tox tox-venv
+- pip install -U virtualenv
+- pip install tox
 
 script: tox