Build backend: Build editable (#9230)

Support for editable installs. This is a simple PEP 660 implementation.

crates/uv-build-backend/src/lib.rs

@@ -357,8 +357,6 @@ pub fn build_wheel(
                 entry.file_type(),
             ));
         }
-
-        entry.path();
     }
 
     // Add the license files
@@ -416,6 +414,63 @@ pub fn build_wheel(
     Ok(filename)
 }
 
+/// Build a wheel from the source tree and place it in the output directory.
+pub fn build_editable(
+    source_tree: &Path,
+    wheel_dir: &Path,
+    metadata_directory: Option<&Path>,
+    uv_version: &str,
+) -> Result<WheelFilename, Error> {
+    let contents = fs_err::read_to_string(source_tree.join("pyproject.toml"))?;
+    let pyproject_toml = PyProjectToml::parse(&contents)?;
+    pyproject_toml.check_build_system("1.0.0+test");
+
+    check_metadata_directory(source_tree, metadata_directory, &pyproject_toml)?;
+
+    let filename = WheelFilename {
+        name: pyproject_toml.name().clone(),
+        version: pyproject_toml.version().clone(),
+        build_tag: None,
+        python_tag: vec!["py3".to_string()],
+        abi_tag: vec!["none".to_string()],
+        platform_tag: vec!["any".to_string()],
+    };
+
+    let wheel_path = wheel_dir.join(filename.to_string());
+    debug!("Writing wheel at {}", wheel_path.user_display());
+    let mut wheel_writer = ZipDirectoryWriter::new_wheel(File::create(&wheel_path)?);
+
+    debug!("Adding pth file to {}", wheel_path.user_display());
+    let module_root = pyproject_toml
+        .wheel_settings()
+        .and_then(|wheel_settings| wheel_settings.module_root.as_deref())
+        .unwrap_or_else(|| Path::new("src"));
+    if module_root.is_absolute() {
+        return Err(Error::AbsoluteModuleRoot(module_root.to_path_buf()));
+    }
+    let src_root = source_tree.join(module_root);
+    let module_root = src_root.join(pyproject_toml.name().as_dist_info_name().as_ref());
+    if !module_root.join("__init__.py").is_file() {
+        return Err(Error::MissingModule(module_root));
+    }
+    wheel_writer.write_bytes(
+        &format!("{}.pth", pyproject_toml.name().as_dist_info_name()),
+        src_root.as_os_str().as_encoded_bytes(),
+    )?;
+
+    debug!("Adding metadata files to: `{}`", wheel_path.user_display());
+    let dist_info_dir = write_dist_info(
+        &mut wheel_writer,
+        &pyproject_toml,
+        &filename,
+        source_tree,
+        uv_version,
+    )?;
+    wheel_writer.close(&dist_info_dir)?;
+
+    Ok(filename)
+}
+
 /// Add the files and directories matching from the source tree matching any of the globs in the
 /// wheel subdirectory.
 fn wheel_subdir_from_globs(

crates/uv/src/commands/build_backend.rs

@@ -1,11 +1,13 @@
 #![allow(clippy::print_stdout)]
 
 use crate::commands::ExitStatus;
-use anyhow::Result;
+use anyhow::{Context, Result};
 use std::env;
+use std::io::Write;
 use std::path::Path;
 use uv_build_backend::SourceDistSettings;
 
+/// PEP 517 hook to build a source distribution.
 pub(crate) fn build_sdist(sdist_directory: &Path) -> Result<ExitStatus> {
     let filename = uv_build_backend::build_source_dist(
         &env::current_dir()?,
@@ -13,9 +15,12 @@ pub(crate) fn build_sdist(sdist_directory: &Path) -> Result<ExitStatus> {
         SourceDistSettings::default(),
         uv_version::version(),
     )?;
-    println!("{filename}");
+    // Tell the build frontend about the name of the artifact we built
+    writeln!(&mut std::io::stdout(), "{filename}").context("stdout is closed")?;
     Ok(ExitStatus::Success)
 }
+
+/// PEP 517 hook to build a wheel.
 pub(crate) fn build_wheel(
     wheel_directory: &Path,
     metadata_directory: Option<&Path>,
@@ -26,38 +31,62 @@ pub(crate) fn build_wheel(
         metadata_directory,
         uv_version::version(),
     )?;
-    println!("{filename}");
+    // Tell the build frontend about the name of the artifact we built
+    writeln!(&mut std::io::stdout(), "{filename}").context("stdout is closed")?;
     Ok(ExitStatus::Success)
 }
 
+/// PEP 660 hook to build a wheel.
 pub(crate) fn build_editable(
-    _wheel_directory: &Path,
-    _metadata_directory: Option<&Path>,
+    wheel_directory: &Path,
+    metadata_directory: Option<&Path>,
 ) -> Result<ExitStatus> {
-    todo!()
+    let filename = uv_build_backend::build_editable(
+        &env::current_dir()?,
+        wheel_directory,
+        metadata_directory,
+        uv_version::version(),
+    )?;
+    // Tell the build frontend about the name of the artifact we built
+    writeln!(&mut std::io::stdout(), "{filename}").context("stdout is closed")?;
+    Ok(ExitStatus::Success)
 }
 
+/// Not used from Python code, exists for symmetry with PEP 517.
 pub(crate) fn get_requires_for_build_sdist() -> Result<ExitStatus> {
-    todo!()
+    unimplemented!("uv does not support extra requires")
 }
 
+/// Not used from Python code, exists for symmetry with PEP 517.
 pub(crate) fn get_requires_for_build_wheel() -> Result<ExitStatus> {
-    todo!()
+    unimplemented!("uv does not support extra requires")
 }
+
+/// PEP 517 hook to just emit metadata through `.dist-info`.
 pub(crate) fn prepare_metadata_for_build_wheel(metadata_directory: &Path) -> Result<ExitStatus> {
     let filename = uv_build_backend::metadata(
         &env::current_dir()?,
         metadata_directory,
         uv_version::version(),
     )?;
-    println!("{filename}");
+    // Tell the build frontend about the name of the artifact we built
+    writeln!(&mut std::io::stdout(), "{filename}").context("stdout is closed")?;
     Ok(ExitStatus::Success)
 }
 
+/// Not used from Python code, exists for symmetry with PEP 660.
 pub(crate) fn get_requires_for_build_editable() -> Result<ExitStatus> {
-    todo!()
+    unimplemented!("uv does not support extra requires")
 }
 
-pub(crate) fn prepare_metadata_for_build_editable(_wheel_directory: &Path) -> Result<ExitStatus> {
-    todo!()
+/// PEP 660 hook to just emit metadata through `.dist-info`.
+pub(crate) fn prepare_metadata_for_build_editable(metadata_directory: &Path) -> Result<ExitStatus> {
+    let filename = uv_build_backend::metadata(
+        &env::current_dir()?,
+        metadata_directory,
+        uv_version::version(),
+    )?;
+    // Tell the build frontend about the name of the artifact we built
+    writeln!(&mut std::io::stdout(), "{filename}").context("stdout is closed")?;
+    Ok(ExitStatus::Success)
 }

crates/uv/tests/it/build_backend.rs

@@ -7,6 +7,7 @@ use indoc::indoc;
 use std::env;
 use std::io::BufReader;
 use std::path::Path;
+use std::process::Command;
 use tempfile::TempDir;
 use uv_static::EnvVars;
 
@@ -142,3 +143,65 @@ fn built_by_uv_direct() -> Result<()> {
 
     Ok(())
 }
+
+/// Test that editables work.
+///
+/// We can't test end-to-end here including the PEP 517 bridge code since we don't have a uv wheel,
+/// so we call the build backend directly.
+#[test]
+fn built_by_uv_editable() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let built_by_uv = Path::new("../../scripts/packages/built-by-uv");
+
+    // Without the editable, pytest fails.
+    context.pip_install().arg("pytest").assert().success();
+    Command::new(context.interpreter())
+        .arg("-m")
+        .arg("pytest")
+        .current_dir(built_by_uv)
+        .assert()
+        .failure();
+
+    // Build and install the editable. Normally, this should be one step with the editable never
+    // been seen, but we have to split it for the test.
+    let wheel_dir = TempDir::new()?;
+    uv_snapshot!(context
+        .build_backend()
+        .arg("build-wheel")
+        .arg(wheel_dir.path())
+        .current_dir(built_by_uv), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    built_by_uv-0.1.0-py3-none-any.whl
+
+    ----- stderr -----
+    "###);
+    context
+        .pip_install()
+        .arg(wheel_dir.path().join("built_by_uv-0.1.0-py3-none-any.whl"))
+        .assert()
+        .success();
+
+    drop(wheel_dir);
+
+    // Now, pytest passes.
+    uv_snapshot!(Command::new(context.interpreter())
+        .arg("-m")
+        .arg("pytest")
+        // Avoid showing absolute paths
+        .arg("--no-header")
+        // Otherwise, the header has a different length on windows
+        .arg("--quiet")
+        .current_dir(built_by_uv), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    ..                                                                       [100%]
+    2 passed in [TIME]
+
+    ----- stderr -----
+    "###);
+
+    Ok(())
+}