Allow --constraint in pip sync

crates/uv/src/cli.rs

@@ -636,6 +636,16 @@ pub(crate) struct PipSyncArgs {
     #[arg(required(true))]
     pub(crate) src_file: Vec<PathBuf>,
 
+    /// Constrain versions using the given requirements files.
+    ///
+    /// Constraints files are `requirements.txt`-like files that only control the _version_ of a
+    /// requirement that's installed. However, including a package in a constraints file will _not_
+    /// trigger the installation of that package.
+    ///
+    /// This is equivalent to pip's `--constraint` option.
+    #[arg(long, short, env = "UV_CONSTRAINT", value_delimiter = ' ', value_parser = parse_file_path)]
+    pub(crate) constraint: Vec<Maybe<PathBuf>>,
+
     /// Reinstall all packages, regardless of whether they're already installed.
     #[arg(long, alias = "force-reinstall", overrides_with("no_reinstall"))]
     pub(crate) reinstall: bool,

crates/uv/src/commands/pip_sync.rs

@@ -46,7 +46,8 @@ use crate::printer::Printer;
 /// Install a set of locked requirements into the current Python environment.
 #[allow(clippy::too_many_arguments, clippy::fn_params_excessive_bools)]
 pub(crate) async fn pip_sync(
-    sources: &[RequirementsSource],
+    requirements: &[RequirementsSource],
+    constraints: &[RequirementsSource],
     reinstall: &Reinstall,
     link_mode: LinkMode,
     compile: bool,
@@ -84,7 +85,7 @@ pub(crate) async fn pip_sync(
     let RequirementsSpecification {
         project: _,
         requirements,
-        constraints: _,
+        constraints,
         overrides: _,
         editables,
         source_trees,
@@ -95,7 +96,15 @@ pub(crate) async fn pip_sync(
         find_links,
         no_binary: specified_no_binary,
         no_build: specified_no_build,
-    } = RequirementsSpecification::from_simple_sources(sources, &client_builder, preview).await?;
+    } = RequirementsSpecification::from_sources(
+        requirements,
+        constraints,
+        &[],
+        &ExtrasSpecification::None,
+        &client_builder,
+        preview,
+    )
+    .await?;
 
     // Validate that the requirements are non-empty.
     let num_requirements = requirements.len() + source_trees.len() + editables.len();

crates/uv/src/main.rs

@@ -248,14 +248,20 @@ async fn run() -> Result<ExitStatus> {
             let args = PipSyncSettings::resolve(args, workspace);
 
             let cache = cache.with_refresh(args.refresh);
-            let sources = args
+            let requirements = args
                 .src_file
                 .into_iter()
                 .map(RequirementsSource::from_requirements_file)
                 .collect::<Vec<_>>();
+            let constraints = args
+                .constraint
+                .into_iter()
+                .map(RequirementsSource::from_constraints_txt)
+                .collect::<Vec<_>>();
 
             commands::pip_sync(
-                &sources,
+                &requirements,
+                &constraints,
                 &args.reinstall,
                 args.shared.link_mode,
                 args.shared.compile_bytecode,

crates/uv/src/settings.rs

@@ -319,6 +319,7 @@ impl PipCompileSettings {
 pub(crate) struct PipSyncSettings {
     // CLI-only settings.
     pub(crate) src_file: Vec<PathBuf>,
+    pub(crate) constraint: Vec<PathBuf>,
     pub(crate) reinstall: Reinstall,
     pub(crate) refresh: Refresh,
 
@@ -331,6 +332,7 @@ impl PipSyncSettings {
     pub(crate) fn resolve(args: PipSyncArgs, workspace: Option<Workspace>) -> Self {
         let PipSyncArgs {
             src_file,
+            constraint,
             reinstall,
             no_reinstall,
             reinstall_package,
@@ -375,6 +377,10 @@ impl PipSyncSettings {
         Self {
             // CLI-only settings.
             src_file,
+            constraint: constraint
+                .into_iter()
+                .filter_map(Maybe::into_option)
+                .collect(),
             reinstall: Reinstall::from_args(flag(reinstall, no_reinstall), reinstall_package),
             refresh: Refresh::from_args(flag(refresh, no_refresh), refresh_package),
 

crates/uv/tests/pip_sync.rs

@@ -2822,6 +2822,63 @@ fn conflicting_requirement() -> Result<()> {
     Ok(())
 }
 
+/// Respect a compatible constraint provided via a `--constraint` file.
+#[test]
+fn constraint_compatible() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("anyio==4.0.0")?;
+
+    let constraints_txt = context.temp_dir.child("constraints.txt");
+    constraints_txt.write_str("anyio<=4.0.0")?;
+
+    uv_snapshot!(command(&context)
+        .arg("requirements.in")
+        .arg("-c")
+        .arg("constraints.txt"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    Downloaded 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + anyio==4.0.0
+    "###);
+
+    Ok(())
+}
+
+/// Respect an incompatible constraint provided via a `--constraint` file by failing the
+/// installation.
+#[test]
+fn constraint_incompatible() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("anyio==4.0.0")?;
+
+    let constraints_txt = context.temp_dir.child("constraints.txt");
+    constraints_txt.write_str("anyio<4.0.0")?;
+
+    uv_snapshot!(command(&context)
+        .arg("requirements.in")
+        .arg("-c")
+        .arg("constraints.txt"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    Downloaded 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + anyio==4.0.0
+    "###);
+
+    Ok(())
+}
+
 /// Don't preserve the mtime from .tar.gz files, it may be the unix epoch (1970-01-01), while Python's zip
 /// implementation can't handle files with an mtime older than 1980.
 /// See also <https://github.com/alexcrichton/tar-rs/issues/349>.