Respect build constraints for workspace members (#18350)

## Summary

These are respected in `uv sync` and `uv pip install`, but not `uv
build`.

Closes https://github.com/astral-sh/uv/issues/18283

crates/uv/src/commands/build_frontend.rs

@@ -24,7 +24,7 @@ use uv_distribution_filename::{
 };
 use uv_distribution_types::{
     ConfigSettings, DependencyMetadata, ExtraBuildVariables, Index, IndexLocations,
-    PackageConfigSettings, RequiresPython, SourceDist,
+    PackageConfigSettings, Requirement, RequiresPython, SourceDist,
 };
 use uv_fs::{Simplified, relative_to};
 use uv_install_wheel::LinkMode;
@@ -113,6 +113,7 @@ pub(crate) async fn build_frontend(
     force_pep517: bool,
     clear: bool,
     build_constraints: Vec<RequirementsSource>,
+    build_constraints_from_workspace: Vec<Requirement>,
     hash_checking: Option<HashCheckingMode>,
     python: Option<String>,
     install_mirrors: PythonInstallMirrors,
@@ -141,6 +142,7 @@ pub(crate) async fn build_frontend(
         force_pep517,
         clear,
         &build_constraints,
+        &build_constraints_from_workspace,
         hash_checking,
         python.as_deref(),
         install_mirrors,
@@ -189,6 +191,7 @@ async fn build_impl(
     force_pep517: bool,
     clear: bool,
     build_constraints: &[RequirementsSource],
+    build_constraints_from_workspace: &[Requirement],
     hash_checking: Option<HashCheckingMode>,
     python_request: Option<&str>,
     install_mirrors: PythonInstallMirrors,
@@ -358,6 +361,7 @@ async fn build_impl(
             force_pep517,
             clear,
             build_constraints,
+            build_constraints_from_workspace,
             build_isolation,
             extra_build_dependencies,
             extra_build_variables,
@@ -468,6 +472,7 @@ async fn build_package(
     force_pep517: bool,
     clear: bool,
     build_constraints: &[RequirementsSource],
+    build_constraints_from_workspace: &[Requirement],
     build_isolation: &BuildIsolation,
     extra_build_dependencies: &ExtraBuildDependencies,
     extra_build_variables: &ExtraBuildVariables,
@@ -571,7 +576,8 @@ async fn build_package(
     let build_constraints = Constraints::from_requirements(
         build_constraints
             .into_iter()
-            .map(|constraint| constraint.requirement),
+            .map(|constraint| constraint.requirement)
+            .chain(build_constraints_from_workspace.iter().cloned()),
     );
 
     // Initialize the registry client.

crates/uv/src/lib.rs

@@ -1173,6 +1173,7 @@ async fn run(mut cli: Cli) -> Result<ExitStatus> {
                 args.force_pep517,
                 args.clear,
                 build_constraints,
+                args.build_constraints_from_workspace,
                 args.hash_checking,
                 args.python,
                 args.install_mirrors,

crates/uv/src/settings.rs

@@ -3364,6 +3364,7 @@ pub(crate) struct BuildSettings {
     pub(crate) force_pep517: bool,
     pub(crate) clear: bool,
     pub(crate) build_constraints: Vec<PathBuf>,
+    pub(crate) build_constraints_from_workspace: Vec<Requirement>,
     pub(crate) hash_checking: Option<HashCheckingMode>,
     pub(crate) python: Option<String>,
     pub(crate) install_mirrors: PythonInstallMirrors,
@@ -3406,6 +3407,19 @@ impl BuildSettings {
             Some(fs) => fs.install_mirrors.clone(),
             None => PythonInstallMirrors::default(),
         };
+        let build_constraints_from_workspace = if let Some(configuration) = &filesystem {
+            configuration
+                .build_constraint_dependencies
+                .clone()
+                .unwrap_or_default()
+                .into_iter()
+                .map(|requirement| {
+                    Requirement::from(requirement.with_origin(RequirementOrigin::Workspace))
+                })
+                .collect()
+        } else {
+            Vec::new()
+        };
 
         Self {
             src,
@@ -3424,6 +3438,7 @@ impl BuildSettings {
                 .into_iter()
                 .filter_map(Maybe::into_option)
                 .collect(),
+            build_constraints_from_workspace,
             hash_checking: HashCheckingMode::from_args(
                 flag(require_hashes, no_require_hashes, "require-hashes"),
                 flag(verify_hashes, no_verify_hashes, "verify-hashes"),

crates/uv/tests/it/build.rs

@@ -7,7 +7,7 @@ use insta::assert_snapshot;
 use predicates::prelude::predicate;
 use std::env::current_dir;
 use uv_static::EnvVars;
-use uv_test::{DEFAULT_PYTHON_VERSION, uv_snapshot};
+use uv_test::{DEFAULT_PYTHON_VERSION, apply_filters, uv_snapshot};
 use zip::ZipArchive;
 
 #[test]
@@ -894,6 +894,190 @@ fn build_constraints() -> Result<()> {
     Ok(())
 }
 
+/// Regression test for <https://github.com/astral-sh/uv/issues/18283>.
+///
+/// `uv build --all` should respect `tool.uv.build-constraint-dependencies` declared at the
+/// workspace root.
+#[test]
+fn build_all_respects_workspace_build_constraint_dependencies() -> Result<()> {
+    let context = uv_test::test_context!("3.12");
+    let filters = context
+        .filters()
+        .into_iter()
+        .chain([(r"\\\.", ""), (r"\[member\]", "[PKG]")])
+        .collect::<Vec<_>>();
+
+    let project = context.temp_dir.child("project");
+
+    project.child("pyproject.toml").write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+
+        [tool.uv]
+        build-constraint-dependencies = ["hatchling==0.1.0"]
+
+        [tool.uv.workspace]
+        members = ["packages/*"]
+        "#,
+    )?;
+
+    project
+        .child("src")
+        .child("project")
+        .child("__init__.py")
+        .touch()?;
+    project.child("README").touch()?;
+
+    let member = project.child("packages").child("member");
+    fs_err::create_dir_all(member.path())?;
+
+    member.child("pyproject.toml").write_str(
+        r#"
+        [project]
+        name = "member"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+
+        [build-system]
+        requires = ["hatchling>=1.0"]
+        build-backend = "hatchling.build"
+        "#,
+    )?;
+
+    member
+        .child("src")
+        .child("member")
+        .child("__init__.py")
+        .touch()?;
+    member.child("README").touch()?;
+
+    let output = context
+        .build()
+        .arg("--all")
+        .arg("--no-build-logs")
+        .current_dir(&project)
+        .output()?;
+
+    let stderr = apply_filters(
+        String::from_utf8_lossy(&output.stderr).into_owned(),
+        &filters,
+    );
+
+    assert!(
+        !output.status.success(),
+        "expected `uv build --all` to fail when workspace build constraints make `hatchling` \
+         unsatisfiable, but it succeeded:\n{stderr}"
+    );
+    assert_eq!(output.status.code(), Some(2));
+    assert!(
+        stderr.contains("Failed to resolve requirements from `build-system.requires`"),
+        "expected build constraint failure in stderr:\n{stderr}"
+    );
+    assert!(
+        stderr.contains(
+            "Because you require hatchling>=1.0 and hatchling==0.1.0, we can conclude that your requirements are unsatisfiable."
+        ),
+        "expected incompatible build constraints in stderr:\n{stderr}"
+    );
+
+    project
+        .child("dist")
+        .child("member-0.1.0.tar.gz")
+        .assert(predicate::path::missing());
+    project
+        .child("dist")
+        .child("member-0.1.0-py3-none-any.whl")
+        .assert(predicate::path::missing());
+
+    Ok(())
+}
+
+/// Limitation: when `uv build` is invoked with an explicit source path, configuration is still
+/// loaded from the invocation directory instead of the source workspace. As a result, workspace
+/// `build-constraint-dependencies` are not applied here.
+#[test]
+fn build_source_path_ignores_workspace_build_constraint_dependencies() -> Result<()> {
+    let context = uv_test::test_context!("3.12");
+    let filters = context
+        .filters()
+        .into_iter()
+        .chain([(r"\\\.", ""), (r"\[member\]", "[PKG]")])
+        .collect::<Vec<_>>();
+
+    let project = context.temp_dir.child("project");
+
+    project.child("pyproject.toml").write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+
+        [tool.uv]
+        build-constraint-dependencies = ["hatchling==0.1.0"]
+
+        [tool.uv.workspace]
+        members = ["packages/*"]
+        "#,
+    )?;
+
+    project
+        .child("src")
+        .child("project")
+        .child("__init__.py")
+        .touch()?;
+    project.child("README").touch()?;
+
+    let member = project.child("packages").child("member");
+    fs_err::create_dir_all(member.path())?;
+
+    member.child("pyproject.toml").write_str(
+        r#"
+        [project]
+        name = "member"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+
+        [build-system]
+        requires = ["hatchling>=1.0"]
+        build-backend = "hatchling.build"
+        "#,
+    )?;
+
+    member
+        .child("src")
+        .child("member")
+        .child("__init__.py")
+        .touch()?;
+    member.child("README").touch()?;
+
+    uv_snapshot!(&filters, context.build().arg("./project").arg("--all").arg("--no-build-logs"), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    [PKG] Building source distribution...
+    [PKG] Building wheel from source distribution...
+    Successfully built project/dist/member-0.1.0.tar.gz
+    Successfully built project/dist/member-0.1.0-py3-none-any.whl
+    ");
+
+    project
+        .child("dist")
+        .child("member-0.1.0.tar.gz")
+        .assert(predicate::path::is_file());
+    project
+        .child("dist")
+        .child("member-0.1.0-py3-none-any.whl")
+        .assert(predicate::path::is_file());
+
+    Ok(())
+}
+
 #[test]
 fn build_sha() -> Result<()> {
     let context = uv_test::test_context!(DEFAULT_PYTHON_VERSION);

crates/uv/tests/it/sync.rs

@@ -12342,6 +12342,102 @@ fn sync_build_constraints() -> Result<()> {
     Ok(())
 }
 
+/// `uv sync --package <member>` should respect workspace build constraints for the selected
+/// member's transitive build dependencies.
+///
+/// See: <https://github.com/astral-sh/uv/issues/12434>
+#[test]
+fn sync_workspace_member_build_constraints() -> Result<()> {
+    let context = uv_test::test_context!("3.12")
+        .with_exclude_newer("2025-03-24T19:00:00Z")
+        .with_filtered_counts();
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "root"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["child"]
+
+        [tool.uv]
+        build-constraint-dependencies = ["setuptools<78"]
+
+        [tool.uv.sources]
+        child = { workspace = true }
+
+        [tool.uv.workspace]
+        members = ["child"]
+        "#,
+    )?;
+    context
+        .temp_dir
+        .child("src")
+        .child("root")
+        .child("__init__.py")
+        .touch()?;
+
+    let child = context.temp_dir.child("child");
+    child.child("pyproject.toml").write_str(
+        r#"
+        [project]
+        name = "child"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["json-merge-patch"]
+
+        [build-system]
+        requires = ["uv_build>=0.7,<10000"]
+        build-backend = "uv_build"
+        "#,
+    )?;
+    child
+        .child("src")
+        .child("child")
+        .child("__init__.py")
+        .touch()?;
+
+    uv_snapshot!(context.filters(), context.sync().arg("--package").arg("child").arg("--no-binary-package").arg("json-merge-patch"), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved [N] packages in [TIME]
+    Prepared [N] packages in [TIME]
+    Installed [N] packages in [TIME]
+     + child==0.1.0 (from file://[TEMP_DIR]/child)
+     + json-merge-patch==0.2
+    ");
+
+    let lock = context.read("uv.lock");
+    assert!(
+        lock.contains(r#"build-constraints = [{ name = "setuptools", specifier = "<78" }]"#),
+        "expected workspace build constraints to be recorded in the lockfile:\n{lock}"
+    );
+
+    fs_err::remove_dir_all(&context.cache_dir)?;
+    fs_err::remove_dir_all(&context.venv)?;
+
+    uv_snapshot!(context.filters(), context.sync().arg("--package").arg("child").arg("--locked").arg("--no-binary-package").arg("json-merge-patch"), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Using CPython 3.12.[X] interpreter at: [PYTHON-3.12]
+    Creating virtual environment at: .venv
+    Resolved [N] packages in [TIME]
+    Prepared [N] packages in [TIME]
+    Installed [N] packages in [TIME]
+     + child==0.1.0 (from file://[TEMP_DIR]/child)
+     + json-merge-patch==0.2
+    ");
+
+    Ok(())
+}
+
 // Test that we recreate a virtual environment when `pyvenv.cfg` version
 // is incompatible with the interpreter version.
 #[test]