Add build backend scaffolding (#7662)

crates/uv-cli/src/lib.rs

@@ -389,6 +389,15 @@ pub enum Commands {
     Build(BuildArgs),
     /// Upload distributions to an index.
     Publish(PublishArgs),
+    /// The implementation of the build backend.
+    ///
+    /// These commands are not directly exposed to the user, instead users invoke their build
+    /// frontend (PEP 517) which calls the Python shims which calls back into uv with this method.
+    #[command(hide = true)]
+    BuildBackend {
+        #[command(subcommand)]
+        command: BuildBackendCommand,
+    },
     /// Manage uv's cache.
     #[command(
         after_help = "Use `uv help cache` for more details.",
@@ -4389,3 +4398,33 @@ pub struct PublishArgs {
     )]
     pub allow_insecure_host: Option<Vec<Maybe<TrustedHost>>>,
 }
+
+/// See [PEP 517](https://peps.python.org/pep-0517/) and
+/// [PEP 660](https://peps.python.org/pep-0660/) for specifications of the parameters.
+#[derive(Subcommand)]
+pub enum BuildBackendCommand {
+    /// PEP 517 hook `build_sdist`.
+    BuildSdist { sdist_directory: PathBuf },
+    /// PEP 517 hook `build_wheel`.
+    BuildWheel {
+        wheel_directory: PathBuf,
+        #[arg(long)]
+        metadata_directory: Option<PathBuf>,
+    },
+    /// PEP 660 hook `build_editable`.
+    BuildEditable {
+        wheel_directory: PathBuf,
+        #[arg(long)]
+        metadata_directory: Option<PathBuf>,
+    },
+    /// PEP 517 hook `get_requires_for_build_sdist`.
+    GetRequiresForBuildSdist,
+    /// PEP 517 hook `get_requires_for_build_wheel`.
+    GetRequiresForBuildWheel,
+    /// PEP 517 hook `prepare_metadata_for_build_wheel`.
+    PrepareMetadataForBuildWheel { wheel_directory: PathBuf },
+    /// PEP 660 hook `get_requires_for_build_editable`.
+    GetRequiresForBuildEditable,
+    /// PEP 660 hook `prepare_metadata_for_build_editable`.
+    PrepareMetadataForBuildEditable { wheel_directory: PathBuf },
+}

crates/uv/src/commands/build_backend.rs

@@ -0,0 +1,41 @@
+use crate::commands::ExitStatus;
+use anyhow::Result;
+use std::path::Path;
+
+pub(crate) fn build_sdist(_sdist_directory: &Path) -> Result<ExitStatus> {
+    todo!()
+}
+
+pub(crate) fn build_wheel(
+    _wheel_directory: &Path,
+    _metadata_directory: Option<&Path>,
+) -> Result<ExitStatus> {
+    todo!()
+}
+
+pub(crate) fn build_editable(
+    _wheel_directory: &Path,
+    _metadata_directory: Option<&Path>,
+) -> Result<ExitStatus> {
+    todo!()
+}
+
+pub(crate) fn get_requires_for_build_sdist() -> Result<ExitStatus> {
+    todo!()
+}
+
+pub(crate) fn get_requires_for_build_wheel() -> Result<ExitStatus> {
+    todo!()
+}
+
+pub(crate) fn prepare_metadata_for_build_wheel(_wheel_directory: &Path) -> Result<ExitStatus> {
+    todo!()
+}
+
+pub(crate) fn get_requires_for_build_editable() -> Result<ExitStatus> {
+    todo!()
+}
+
+pub(crate) fn prepare_metadata_for_build_editable(_wheel_directory: &Path) -> Result<ExitStatus> {
+    todo!()
+}

crates/uv/src/commands/mod.rs

@@ -60,20 +60,20 @@ pub(crate) use version::version;
 
 use crate::printer::Printer;
 
+mod build;
+pub(crate) mod build_backend;
 mod cache_clean;
 mod cache_dir;
 mod cache_prune;
 mod help;
 pub(crate) mod pip;
 mod project;
+mod publish;
 mod python;
 pub(crate) mod reporters;
-mod tool;
-
-mod build;
-mod publish;
 #[cfg(feature = "self-update")]
 mod self_update;
+mod tool;
 mod venv;
 mod version;
 

crates/uv/src/lib.rs

@@ -15,8 +15,8 @@ use tracing::{debug, instrument};
 use uv_cache::{Cache, Refresh};
 use uv_cache_info::Timestamp;
 use uv_cli::{
-    compat::CompatArgs, CacheCommand, CacheNamespace, Cli, Commands, PipCommand, PipNamespace,
-    ProjectCommand,
+    compat::CompatArgs, BuildBackendCommand, CacheCommand, CacheNamespace, Cli, Commands,
+    PipCommand, PipNamespace, ProjectCommand,
 };
 use uv_cli::{PythonCommand, PythonNamespace, ToolCommand, ToolNamespace, TopLevelArgs};
 #[cfg(feature = "self-update")]
@@ -1118,6 +1118,40 @@ async fn run(cli: Cli) -> Result<ExitStatus> {
             )
             .await
         }
+        Commands::BuildBackend { command } => match command {
+            BuildBackendCommand::BuildSdist { sdist_directory } => {
+                commands::build_backend::build_sdist(&sdist_directory)
+            }
+            BuildBackendCommand::BuildWheel {
+                wheel_directory,
+                metadata_directory,
+            } => commands::build_backend::build_wheel(
+                &wheel_directory,
+                metadata_directory.as_deref(),
+            ),
+            BuildBackendCommand::BuildEditable {
+                wheel_directory,
+                metadata_directory,
+            } => commands::build_backend::build_editable(
+                &wheel_directory,
+                metadata_directory.as_deref(),
+            ),
+            BuildBackendCommand::GetRequiresForBuildSdist => {
+                commands::build_backend::get_requires_for_build_sdist()
+            }
+            BuildBackendCommand::GetRequiresForBuildWheel => {
+                commands::build_backend::get_requires_for_build_wheel()
+            }
+            BuildBackendCommand::PrepareMetadataForBuildWheel { wheel_directory } => {
+                commands::build_backend::prepare_metadata_for_build_wheel(&wheel_directory)
+            }
+            BuildBackendCommand::GetRequiresForBuildEditable => {
+                commands::build_backend::get_requires_for_build_editable()
+            }
+            BuildBackendCommand::PrepareMetadataForBuildEditable { wheel_directory } => {
+                commands::build_backend::prepare_metadata_for_build_editable(&wheel_directory)
+            }
+        },
     }
 }
 

python/uv/__init__.py

@@ -1,41 +1,30 @@
 from __future__ import annotations
 
 import os
-import sys
-import sysconfig
 
+if os.environ.get("UV_PREVIEW"):
+    from ._build_backend import *
+from ._find_uv import find_uv_bin
 
-def find_uv_bin() -> str:
-    """Return the uv binary path."""
-
-    uv_exe = "uv" + sysconfig.get_config_var("EXE")
-
-    path = os.path.join(sysconfig.get_path("scripts"), uv_exe)
-    if os.path.isfile(path):
-        return path
-
-    if sys.version_info >= (3, 10):
-        user_scheme = sysconfig.get_preferred_scheme("user")
-    elif os.name == "nt":
-        user_scheme = "nt_user"
-    elif sys.platform == "darwin" and sys._framework:
-        user_scheme = "osx_framework_user"
-    else:
-        user_scheme = "posix_user"
-
-    path = os.path.join(sysconfig.get_path("scripts", scheme=user_scheme), uv_exe)
-    if os.path.isfile(path):
-        return path
-
-    # Search in `bin` adjacent to package root (as created by `pip install --target`).
-    pkg_root = os.path.dirname(os.path.dirname(__file__))
-    target_path = os.path.join(pkg_root, "bin", uv_exe)
-    if os.path.isfile(target_path):
-        return target_path
-
-    raise FileNotFoundError(path)
-
-
-__all__ = [
-    "find_uv_bin",
-]
+if os.environ.get("UV_PREVIEW"):
+    __all__ = [
+        "find_uv_bin",
+        # PEP 517 hook `build_sdist`.
+        "build_sdist",
+        # PEP 517 hook `build_wheel`.
+        "build_wheel",
+        # PEP 660 hook `build_editable`.
+        "build_editable",
+        # PEP 517 hook `get_requires_for_build_sdist`.
+        "get_requires_for_build_sdist",
+        # PEP 517 hook `get_requires_for_build_wheel`.
+        "get_requires_for_build_wheel",
+        # PEP 517 hook `prepare_metadata_for_build_wheel`.
+        "prepare_metadata_for_build_wheel",
+        # PEP 660 hook `get_requires_for_build_editable`.
+        "get_requires_for_build_editable",
+        # PEP 660 hook `prepare_metadata_for_build_editable`.
+        "prepare_metadata_for_build_editable",
+    ]
+else:
+    __all__ = ["find_uv_bin"]

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)

python/uv/_find_uv.py

@@ -0,0 +1,36 @@
+from __future__ import annotations
+
+import os
+import sys
+import sysconfig
+
+
+def find_uv_bin() -> str:
+    """Return the uv binary path."""
+
+    uv_exe = "uv" + sysconfig.get_config_var("EXE")
+
+    path = os.path.join(sysconfig.get_path("scripts"), uv_exe)
+    if os.path.isfile(path):
+        return path
+
+    if sys.version_info >= (3, 10):
+        user_scheme = sysconfig.get_preferred_scheme("user")
+    elif os.name == "nt":
+        user_scheme = "nt_user"
+    elif sys.platform == "darwin" and sys._framework:
+        user_scheme = "osx_framework_user"
+    else:
+        user_scheme = "posix_user"
+
+    path = os.path.join(sysconfig.get_path("scripts", scheme=user_scheme), uv_exe)
+    if os.path.isfile(path):
+        return path
+
+    # Search in `bin` adjacent to package root (as created by `pip install --target`).
+    pkg_root = os.path.dirname(os.path.dirname(__file__))
+    target_path = os.path.join(pkg_root, "bin", uv_exe)
+    if os.path.isfile(target_path):
+        return target_path
+
+    raise FileNotFoundError(path)

scripts/packages/uv_backend/.gitignore

@@ -0,0 +1 @@
+dist/

scripts/packages/uv_backend/README.md

@@ -0,0 +1,3 @@
+# uv_backend
+
+A simple package to be built with the uv build backend.

scripts/packages/uv_backend/pyproject.toml

@@ -0,0 +1,11 @@
+[project]
+name = "uv-backend"
+version = "0.1.0"
+description = "Add your description here"
+readme = "README.md"
+requires-python = ">=3.12"
+dependencies = []
+
+[build-system]
+requires = ["uv>=0.4.15,<5"]
+build-backend = "uv"

scripts/packages/uv_backend/src/uv_backend/__init__.py

@@ -0,0 +1,2 @@
+def greet():
+    print("Hello 👋")