Add PEP-517 compliant build api

poetry/masonry/api.py

+"""
+PEP-517 compliant buildsystem API
+"""
+import logging
+from pathlib import Path
+
+from poetry import Poetry
+from poetry.io import NullIO
+
+from .builders import SdistBuilder
+from .builders import WheelBuilder
+
+log = logging.getLogger(__name__)
+
+# PEP 517 specifies that the CWD will always be the source tree
+poetry = Poetry.create('.')
+
+
+def get_requires_for_build_wheel(config_settings=None):
+    """
+    Returns a list of requirements for building, as strings
+    """
+    main, extras = SdistBuilder.convert_dependencies(poetry.package.requires)
+
+    return main + extras
+
+
+# For now, we require all dependencies to build either a wheel or an sdist.
+get_requires_for_build_sdist = get_requires_for_build_wheel
+
+
+def build_wheel(wheel_directory, config_settings=None, metadata_directory=None):
+    """Builds a wheel, places it in wheel_directory"""
+    info = WheelBuilder.make_in(poetry, NullIO(), Path(wheel_directory))
+
+    return info.file.name
+
+
+def build_sdist(sdist_directory, config_settings=None):
+    """Builds an sdist, places it in sdist_directory"""
+    path = SdistBuilder(poetry, NullIO()).build(Path(sdist_directory))
+
+    return path.name