Accept --build-constraints in uv build

crates/uv-cli/src/lib.rs

@@ -1979,6 +1979,15 @@ pub struct BuildArgs {
     #[arg(long)]
     pub wheel: bool,
 
+    /// Constrain build dependencies using the given requirements files when building
+    /// distributions.
+    ///
+    /// Constraints files are `requirements.txt`-like files that only control the _version_ of a
+    /// build dependency that's installed. However, including a package in a constraints file will
+    /// _not_ trigger the inclusion of that package on its own.
+    #[arg(long, short, env = "UV_BUILD_CONSTRAINT", value_delimiter = ' ', value_parser = parse_maybe_file_path)]
+    pub build_constraint: Vec<Maybe<PathBuf>>,
+
     /// The Python interpreter to use for the build environment.
     ///
     /// By default, builds are executed in isolated virtual environments. The

crates/uv/src/commands/build.rs

@@ -5,6 +5,7 @@ use crate::printer::Printer;
 use crate::settings::{ResolverSettings, ResolverSettingsRef};
 use std::borrow::Cow;
 
+use crate::commands::pip::operations;
 use anyhow::Result;
 use distribution_filename::SourceDistExtension;
 use owo_colors::OwoColorize;
@@ -20,6 +21,7 @@ use uv_python::{
     EnvironmentPreference, PythonDownloads, PythonEnvironment, PythonInstallation,
     PythonPreference, PythonRequest, PythonVersionFile, VersionRequest,
 };
+use uv_requirements::RequirementsSource;
 use uv_resolver::{FlatIndex, RequiresPython};
 use uv_types::{BuildContext, BuildIsolation, HashStrategy};
 use uv_workspace::{DiscoveryOptions, Workspace};
@@ -32,6 +34,7 @@ pub(crate) async fn build(
     output_dir: Option<PathBuf>,
     sdist: bool,
     wheel: bool,
+    build_constraints: Vec<RequirementsSource>,
     python: Option<String>,
     settings: ResolverSettings,
     no_config: bool,
@@ -49,6 +52,7 @@ pub(crate) async fn build(
         output_dir.as_deref(),
         sdist,
         wheel,
+        &build_constraints,
         python.as_deref(),
         settings.as_ref(),
         no_config,
@@ -88,6 +92,7 @@ async fn build_impl(
     output_dir: Option<&Path>,
     sdist: bool,
     wheel: bool,
+    build_constraints: &[RequirementsSource],
     python_request: Option<&str>,
     settings: ResolverSettingsRef<'_>,
     no_config: bool,
@@ -225,6 +230,10 @@ async fn build_impl(
         store_credentials_from_url(url);
     }
 
+    // Read build constraints.
+    let build_constraints =
+        operations::read_constraints(build_constraints, &client_builder).await?;
+
     // Initialize the registry client.
     let client = RegistryClientBuilder::new(cache.clone())
         .native_tls(native_tls)
@@ -251,8 +260,6 @@ async fn build_impl(
 
     // TODO(charlie): These are all default values. We should consider whether we want to make them
     // optional on the downstream APIs.
-    let build_constraints = Constraints::default();
-    let build_hasher = HashStrategy::default();
     let hasher = HashStrategy::None;
 
     // Resolve the flat indexes from `--find-links`.

crates/uv/src/lib.rs

@@ -670,12 +670,20 @@ async fn run(cli: Cli) -> Result<ExitStatus> {
                     .combine(Refresh::from(args.settings.upgrade.clone())),
             );
 
+            // Resolve the build constraints.
+            let build_constraints = args
+                .build_constraint
+                .into_iter()
+                .map(RequirementsSource::from_constraints_txt)
+                .collect::<Vec<_>>();
+
             commands::build(
                 args.src,
                 args.package,
                 args.out_dir,
                 args.sdist,
                 args.wheel,
+                build_constraints,
                 args.python,
                 args.settings,
                 cli.no_config,

crates/uv/src/settings.rs

@@ -1629,6 +1629,7 @@ pub(crate) struct BuildSettings {
     pub(crate) out_dir: Option<PathBuf>,
     pub(crate) sdist: bool,
     pub(crate) wheel: bool,
+    pub(crate) build_constraint: Vec<PathBuf>,
     pub(crate) python: Option<String>,
     pub(crate) refresh: Refresh,
     pub(crate) settings: ResolverSettings,
@@ -1643,6 +1644,7 @@ impl BuildSettings {
             package,
             sdist,
             wheel,
+            build_constraint,
             python,
             build,
             refresh,
@@ -1655,6 +1657,10 @@ impl BuildSettings {
             out_dir,
             sdist,
             wheel,
+            build_constraint: build_constraint
+                .into_iter()
+                .filter_map(Maybe::into_option)
+                .collect(),
             python,
             refresh: Refresh::from(refresh),
             settings: ResolverSettings::combine(resolver_options(resolver, build), filesystem),

crates/uv/tests/build.rs

@@ -1146,3 +1146,63 @@ fn workspace() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn build_constraints() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let filters = context
+        .filters()
+        .into_iter()
+        .chain([
+            (r"exit code: 1", "exit status: 1"),
+            (r"bdist\.[^/\\\s]+-[^/\\\s]+", "bdist.linux-x86_64"),
+            (r"\\\.", ""),
+        ])
+        .collect::<Vec<_>>();
+
+    let project = context.temp_dir.child("project");
+
+    let constraints = project.child("constraints.txt");
+    constraints.write_str("setuptools==0.1.0")?;
+
+    let pyproject_toml = project.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42"]
+        build-backend = "setuptools.build_meta"
+        "#,
+    )?;
+
+    project.child("src").child("__init__.py").touch()?;
+    project.child("README").touch()?;
+
+    uv_snapshot!(&filters, context.build().arg("--build-constraint").arg("constraints.txt").current_dir(&project), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    Building source distribution...
+    error: Failed to install requirements from `build-system.requires` (resolve)
+      Caused by: No solution found when resolving: setuptools>=42
+      Caused by: Because you require setuptools>=42 and setuptools==0.1.0, we can conclude that your requirements are unsatisfiable.
+    "###);
+
+    project
+        .child("dist")
+        .child("project-0.1.0.tar.gz")
+        .assert(predicate::path::missing());
+    project
+        .child("dist")
+        .child("project-0.1.0-py3-none-any.whl")
+        .assert(predicate::path::missing());
+
+    Ok(())
+}

docs/reference/cli.md

@@ -6225,6 +6225,11 @@ uv build [OPTIONS] [SRC]
 <p>WARNING: Hosts included in this list will not be verified against the system&#8217;s certificate store. Only use <code>--allow-insecure-host</code> in a secure network with verified sources, as it bypasses SSL verification and could expose you to MITM attacks.</p>
 
 <p>May also be set with the <code>UV_INSECURE_HOST</code> environment variable.</p>
+</dd><dt><code>--build-constraint</code>, <code>-b</code> <i>build-constraint</i></dt><dd><p>Constrain build dependencies using the given requirements files when building distributions.</p>
+
+<p>Constraints files are <code>requirements.txt</code>-like files that only control the <em>version</em> of a build dependency that&#8217;s installed. However, including a package in a constraints file will <em>not</em> trigger the inclusion of that package on its own.</p>
+
+<p>May also be set with the <code>UV_BUILD_CONSTRAINT</code> environment variable.</p>
 </dd><dt><code>--cache-dir</code> <i>cache-dir</i></dt><dd><p>Path to the cache directory.</p>
 
 <p>Defaults to <code>$HOME/Library/Caches/uv</code> on macOS, <code>$XDG_CACHE_HOME/uv</code> or <code>$HOME/.cache/uv</code> on Linux, and <code>%LOCALAPPDATA%\uv\cache</code> on Windows.</p>