build backend: use custom wrapper around flit

For pkgcore we need to run multiple preparations of generating files
before creating sdist or wheel. Flit is a very simple and nice build
backend, much more than setuptools.

Signed-off-by: Arthur Zamarin <arthurzam@gentoo.org>

1 files changed, 99 insertions, 0 deletions

diff --git a/py_build.py b/py_build.py
new file mode 100644
index 000000000..f844b1c2a
--- /dev/null
+++ b/py_build.py
@@ -0,0 +1,99 @@
+import os
+import subprocess
+import sys
+import textwrap
+from contextlib import contextmanager
+from functools import partial
+from pathlib import Path
+
+from flit_core import buildapi
+
+
+@contextmanager
+def sys_path():
+    orig_path = sys.path[:]
+    sys.path.insert(0, str(Path.cwd() / 'src'))
+    try:
+        yield
+    finally:
+        sys.path = orig_path
+
+
+def write_pkgcore_lookup_configs(cleanup_files):
+    """Generate file of install path constants."""
+    cleanup_files.append(path := Path.cwd() / "src/pkgcore/_const.py")
+    path.parent.mkdir(parents=True, exist_ok=True)
+    print(f"writing lookup config to {path}")
+
+    with open(path, "w") as f:
+        os.chmod(path, 0o644)
+        f.write(textwrap.dedent("""\
+            from os.path import join, abspath
+            import sys
+
+            from snakeoil import process
+
+            INSTALL_PREFIX = abspath(sys.prefix)
+            DATA_PATH = join(INSTALL_PREFIX, 'share/pkgcore')
+            CONFIG_PATH = join(DATA_PATH, 'config')
+            LIBDIR_PATH = join(INSTALL_PREFIX, 'lib/pkgcore')
+            EBD_PATH = join(LIBDIR_PATH, 'ebd')
+            INJECTED_BIN_PATH = ()
+        """))
+
+
+def write_verinfo(cleanup_files):
+    cleanup_files.append(path := Path.cwd() / "src/pkgcore/_verinfo.py")
+    path.parent.mkdir(parents=True, exist_ok=True)
+    print(f"generating version info: {path}")
+    from snakeoil.version import get_git_version
+    path.write_text(f"version_info={get_git_version(Path.cwd())!r}")
+
+
+def prepare_pkgcore(callback, consts: bool, plugincache: bool):
+    cleanup_files = []
+    try:
+        with sys_path():
+            write_verinfo(cleanup_files)
+
+            # Install module plugincache
+            if plugincache:
+                from pkgcore import plugin, plugins
+                print('Generating plugin cache')
+                cleanup_files.append(path := Path.cwd() / "src/pkgcore/plugins")
+                plugin.initialize_cache(plugins, force=True, cache_dir=path)
+
+            # Install configuration data so pkgcore knows where to find its content,
+            # rather than assuming it is running from a tarball/git repo.
+            if consts:
+                write_pkgcore_lookup_configs(cleanup_files)
+
+            # generate function lists so they don't need to be created on install
+            if subprocess.call(['make', f'PYTHON={sys.executable}'], cwd=Path.cwd() / 'data/lib/pkgcore/ebd'):
+                raise Exception("Running makefile failed")
+
+            return callback()
+    finally:
+        for path in cleanup_files:
+            try:
+                path.unlink()
+            except OSError:
+                pass
+
+
+def build_wheel(wheel_directory, config_settings=None, metadata_directory=None):
+    """Builds a wheel, places it in wheel_directory"""
+    callback = partial(buildapi.build_wheel, wheel_directory, config_settings, metadata_directory)
+    return prepare_pkgcore(callback, consts=True, plugincache=True)
+
+
+def build_editable(wheel_directory, config_settings=None, metadata_directory=None):
+    """Builds an "editable" wheel, places it in wheel_directory"""
+    callback = partial(buildapi.build_editable, wheel_directory, config_settings, metadata_directory)
+    return prepare_pkgcore(callback, consts=False, plugincache=True)
+
+
+def build_sdist(sdist_directory, config_settings=None):
+    """Builds an sdist, places it in sdist_directory"""
+    callback = partial(buildapi.build_sdist, sdist_directory, config_settings)
+    return prepare_pkgcore(callback, consts=False, plugincache=False)