Add build backend scaffolding (#7662)

python/uv/_build_backend.py

@@ -0,0 +1,110 @@
+"""
+Python shims for the PEP 517 and PEP 660 build backend.
+
+Major imports in this module are required to be lazy:
+```
+$ hyperfine \
+     "/usr/bin/python3 -c \"print('hi')\"" \
+     "/usr/bin/python3 -c \"from subprocess import check_call; print('hi')\""
+Base: Time (mean ± σ):      11.0 ms ±   1.7 ms    [User: 8.5 ms, System: 2.5 ms]
+With import: Time (mean ± σ):      15.2 ms ±   2.0 ms    [User: 12.3 ms, System: 2.9 ms]
+Base 1.38 ± 0.28 times faster than with import
+```
+
+The same thing goes for the typing module, so we use Python 3.10 type annotations that
+don't require importing typing but then quote them so earlier Python version ignore
+them while IDEs and type checker can see through the quotes.
+"""
+
+
+def warn_config_settings(config_settings: "dict | None" = None):
+    import sys
+
+    if config_settings:
+        print("Warning: Config settings are not supported", file=sys.stderr)
+
+
+def call(args: "list[str]", config_settings: "dict | None" = None) -> str:
+    """Invoke a uv subprocess and return the filename from stdout."""
+    import subprocess
+    import sys
+
+    from ._find_uv import find_uv_bin
+
+    warn_config_settings(config_settings)
+    # Forward stderr, capture stdout for the filename
+    result = subprocess.run([find_uv_bin()] + args, stdout=subprocess.PIPE)
+    if result.returncode != 0:
+        sys.exit(result.returncode)
+    # If there was extra stdout, forward it (there should not be extra stdout)
+    result = result.stdout.decode("utf-8").strip().splitlines(keepends=True)
+    sys.stdout.writelines(result[:-1])
+    # Fail explicitly instead of an irrelevant stacktrace
+    if not result:
+        print("uv subprocess did not return a filename on stdout", file=sys.stderr)
+        sys.exit(1)
+    return result[-1].strip()
+
+
+def build_sdist(sdist_directory: str, config_settings: "dict | None" = None):
+    """PEP 517 hook `build_sdist`."""
+    args = ["build-backend", "build-sdist", sdist_directory]
+    return call(args, config_settings)
+
+
+def build_wheel(
+    wheel_directory: str,
+    config_settings: "dict | None" = None,
+    metadata_directory: "str | None" = None,
+):
+    """PEP 517 hook `build_wheel`."""
+    args = ["build-backend", "build-wheel", wheel_directory]
+    if metadata_directory:
+        args.extend(["--metadata-directory", metadata_directory])
+    return call(args, config_settings)
+
+
+def get_requires_for_build_sdist(config_settings: "dict | None" = None):
+    """PEP 517 hook `get_requires_for_build_sdist`."""
+    warn_config_settings(config_settings)
+    return []
+
+
+def get_requires_for_build_wheel(config_settings: "dict | None" = None):
+    """PEP 517 hook `get_requires_for_build_wheel`."""
+    warn_config_settings(config_settings)
+    return []
+
+
+def prepare_metadata_for_build_wheel(
+    metadata_directory: str, config_settings: "dict | None" = None
+):
+    """PEP 517 hook `prepare_metadata_for_build_wheel`."""
+    args = ["build-backend", "prepare-metadata-for-build-wheel", metadata_directory]
+    return call(args, config_settings)
+
+
+def build_editable(
+    wheel_directory: str,
+    config_settings: "dict | None" = None,
+    metadata_directory: "str | None" = None,
+):
+    """PEP 660 hook `build_editable`."""
+    args = ["build-backend", "build-editable", wheel_directory]
+    if metadata_directory:
+        args.extend(["--metadata-directory", metadata_directory])
+    return call(args, config_settings)
+
+
+def get_requires_for_build_editable(config_settings: "dict | None" = None):
+    """PEP 660 hook `get_requires_for_build_editable`."""
+    warn_config_settings(config_settings)
+    return []
+
+
+def prepare_metadata_for_build_editable(
+    metadata_directory: str, config_settings: "dict | None" = None
+):
+    """PEP 660 hook `prepare_metadata_for_build_editable`."""
+    args = ["build-backend", "prepare-metadata-for-build-editable", metadata_directory]
+    return call(args, config_settings)