Build and install workspace members that are dependencies by default

crates/uv-distribution/src/metadata/lowering.rs

@@ -306,7 +306,9 @@ impl LoweredRequirement {
                                     },
                                     url,
                                 }
-                            } else if member.pyproject_toml().is_package() {
+                            // We don't require a build system, because the workspace member is a
+                            // dependency
+                            } else if member.pyproject_toml().is_package(false) {
                                 RequirementSource::Directory {
                                     install_path: install_path.into_boxed_path(),
                                     url,
@@ -736,7 +738,8 @@ fn path_source(
                 fs_err::read_to_string(&pyproject_path)
                     .ok()
                     .and_then(|contents| PyProjectToml::from_string(contents).ok())
-                    .and_then(|pyproject_toml| pyproject_toml.tool_uv_package())
+                    // We don't require a build system for path dependencies
+                    .map(|pyproject_toml| pyproject_toml.is_package(false))
                     .unwrap_or(true)
             });
 

crates/uv-resolver/src/lock/mod.rs

@@ -1255,6 +1255,7 @@ impl Lock {
         root: &Path,
         packages: &BTreeMap<PackageName, WorkspaceMember>,
         members: &[PackageName],
+        required_members: BTreeSet<&PackageName>,
         requirements: &[Requirement],
         constraints: &[Requirement],
         overrides: &[Requirement],
@@ -1282,7 +1283,10 @@ impl Lock {
         // Validate that the member sources have not changed (e.g., that they've switched from
         // virtual to non-virtual or vice versa).
         for (name, member) in packages {
-            let expected = !member.pyproject_toml().is_package();
+            // We don't require a build system, if the workspace member is a dependency
+            let expected = !member
+                .pyproject_toml()
+                .is_package(!required_members.contains(name));
             let actual = self
                 .find_by_name(name)
                 .ok()

crates/uv-workspace/src/pyproject.rs

@@ -66,7 +66,7 @@ pub struct PyProjectToml {
 
     /// Used to determine whether a `build-system` section is present.
     #[serde(default, skip_serializing)]
-    build_system: Option<serde::de::IgnoredAny>,
+    pub build_system: Option<serde::de::IgnoredAny>,
 }
 
 impl PyProjectToml {
@@ -81,18 +81,18 @@ impl PyProjectToml {
 
     /// Returns `true` if the project should be considered a Python package, as opposed to a
     /// non-package ("virtual") project.
-    pub fn is_package(&self) -> bool {
+    pub fn is_package(&self, require_build_system: bool) -> bool {
         // If `tool.uv.package` is set, defer to that explicit setting.
         if let Some(is_package) = self.tool_uv_package() {
             return is_package;
         }
 
         // Otherwise, a project is assumed to be a package if `build-system` is present.
-        self.build_system.is_some()
+        self.build_system.is_some() || !require_build_system
     }
 
     /// Returns the value of `tool.uv.package` if set.
-    pub fn tool_uv_package(&self) -> Option<bool> {
+    fn tool_uv_package(&self) -> Option<bool> {
         self.tool
             .as_ref()
             .and_then(|tool| tool.uv.as_ref())

crates/uv-workspace/src/workspace.rs

@@ -20,7 +20,7 @@ use uv_warnings::warn_user_once;
 
 use crate::dependency_groups::{DependencyGroupError, FlatDependencyGroup, FlatDependencyGroups};
 use crate::pyproject::{
-    Project, PyProjectToml, PyprojectTomlError, Sources, ToolUvSources, ToolUvWorkspace,
+    Project, PyProjectToml, PyprojectTomlError, Source, Sources, ToolUvSources, ToolUvWorkspace,
 };
 
 type WorkspaceMembers = Arc<BTreeMap<PackageName, WorkspaceMember>>;
@@ -260,6 +260,7 @@ impl Workspace {
         pyproject_toml: PyProjectToml,
     ) -> Option<Self> {
         let mut packages = self.packages;
+
         let member = Arc::make_mut(&mut packages).get_mut(package_name)?;
 
         if member.root == self.install_path {
@@ -303,7 +304,7 @@ impl Workspace {
 
     /// Returns the set of all workspace members.
     pub fn members_requirements(&self) -> impl Iterator<Item = Requirement> + '_ {
-        self.packages.values().filter_map(|member| {
+        self.packages.iter().filter_map(|(name, member)| {
             let url = VerbatimUrl::from_absolute_path(&member.root)
                 .expect("path is valid URL")
                 .with_given(member.root.to_string_lossy());
@@ -312,7 +313,10 @@ impl Workspace {
                 extras: Box::new([]),
                 groups: Box::new([]),
                 marker: MarkerTree::TRUE,
-                source: if member.pyproject_toml.is_package() {
+                source: if member
+                    .pyproject_toml()
+                    .is_package(!self.is_required_member(name))
+                {
                     RequirementSource::Directory {
                         install_path: member.root.clone().into_boxed_path(),
                         editable: Some(true),
@@ -332,9 +336,40 @@ impl Workspace {
         })
     }
 
+    /// Whether a given workspace member is required by another member.
+    pub fn required_members(&self) -> impl Iterator<Item = &PackageName> + '_ {
+        self.sources
+            .iter()
+            .chain(
+                self.packages
+                    .values()
+                    .filter_map(|member| {
+                        member
+                            .pyproject_toml
+                            .tool
+                            .as_ref()
+                            .and_then(|tool| tool.uv.as_ref())
+                            .and_then(|uv| uv.sources.as_ref())
+                            .map(ToolUvSources::inner)
+                    })
+                    .flatten(),
+            )
+            .filter_map(|(package, sources)| {
+                sources
+                    .iter()
+                    .any(|source| matches!(source, Source::Workspace { .. }))
+                    .then_some(package)
+            })
+    }
+
+    /// Whether a given workspace member is required by another member.
+    pub fn is_required_member(&self, name: &PackageName) -> bool {
+        self.required_members().any(|package| package == name)
+    }
+
     /// Returns the set of all workspace member dependency groups.
     pub fn group_requirements(&self) -> impl Iterator<Item = Requirement> + '_ {
-        self.packages.values().filter_map(|member| {
+        self.packages.iter().filter_map(|(name, member)| {
             let url = VerbatimUrl::from_absolute_path(&member.root)
                 .expect("path is valid URL")
                 .with_given(member.root.to_string_lossy());
@@ -368,7 +403,10 @@ impl Workspace {
                 extras: Box::new([]),
                 groups: groups.into_boxed_slice(),
                 marker: MarkerTree::TRUE,
-                source: if member.pyproject_toml.is_package() {
+                source: if member
+                    .pyproject_toml()
+                    .is_package(!self.is_required_member(name))
+                {
                     RequirementSource::Directory {
                         install_path: member.root.clone().into_boxed_path(),
                         editable: Some(true),

crates/uv/src/commands/build_frontend.rs

@@ -263,7 +263,7 @@ async fn build_impl(
             .get(package)
             .ok_or_else(|| anyhow::anyhow!("Package `{package}` not found in workspace"))?;
 
-        if !package.pyproject_toml().is_package() {
+        if !package.pyproject_toml().is_package(true) {
             let name = &package.project().name;
             let pyproject_toml = package.root().join("pyproject.toml");
             return Err(anyhow::anyhow!(
@@ -300,7 +300,7 @@ async fn build_impl(
         let packages: Vec<_> = workspace
             .packages()
             .values()
-            .filter(|package| package.pyproject_toml().is_package())
+            .filter(|package| package.pyproject_toml().is_package(true))
             .map(|package| AnnotatedSource {
                 source: Source::Directory(Cow::Borrowed(package.root())),
                 package: Some(package.project().name.clone()),

crates/uv/src/commands/project/lock.rs

@@ -444,6 +444,7 @@ async fn do_lock(
     // Collect the requirements, etc.
     let members = target.members();
     let packages = target.packages();
+    let required_members = target.required_members();
     let requirements = target.requirements();
     let overrides = target.overrides();
     let constraints = target.constraints();
@@ -693,6 +694,7 @@ async fn do_lock(
             target.install_path(),
             packages,
             &members,
+            required_members,
             &requirements,
             &dependency_groups,
             &constraints,
@@ -906,6 +908,7 @@ impl ValidatedLock {
         install_path: &Path,
         packages: &BTreeMap<PackageName, WorkspaceMember>,
         members: &[PackageName],
+        required_members: BTreeSet<&PackageName>,
         requirements: &[Requirement],
         dependency_groups: &BTreeMap<GroupName, Vec<Requirement>>,
         constraints: &[Requirement],
@@ -1117,6 +1120,7 @@ impl ValidatedLock {
                 install_path,
                 packages,
                 members,
+                required_members,
                 requirements,
                 constraints,
                 overrides,

crates/uv/src/commands/project/lock_target.rs

@@ -1,4 +1,4 @@
-use std::collections::BTreeMap;
+use std::collections::{BTreeMap, BTreeSet};
 use std::path::{Path, PathBuf};
 
 use itertools::Either;
@@ -154,6 +154,18 @@ impl<'lock> LockTarget<'lock> {
         }
     }
 
+    /// Return the set of required workspace members, i.e., those that are required by other
+    /// members.
+    pub(crate) fn required_members(self) -> BTreeSet<&'lock PackageName> {
+        match self {
+            Self::Workspace(workspace) => workspace.required_members().collect(),
+            Self::Script(_) => {
+                static EMPTY: BTreeSet<&PackageName> = BTreeSet::new();
+                EMPTY.clone()
+            }
+        }
+    }
+
     /// Returns the set of supported environments for the [`LockTarget`].
     pub(crate) fn environments(self) -> Option<&'lock SupportedEnvironments> {
         match self {

crates/uv/src/commands/project/sync.rs

@@ -117,7 +117,7 @@ pub(crate) async fn sync(
         // TODO(lucab): improve warning content
         // <https://github.com/astral-sh/uv/issues/7428>
         if project.workspace().pyproject_toml().has_scripts()
-            && !project.workspace().pyproject_toml().is_package()
+            && !project.workspace().pyproject_toml().is_package(true)
         {
             warn_user!(
                 "Skipping installation of entry points (`project.scripts`) because this project is not packaged; to install entry points, set `tool.uv.package = true` or define a `build-system`"

crates/uv/tests/it/edit.rs

@@ -10351,8 +10351,9 @@ fn add_self() -> Result<()> {
 
     ----- stderr -----
     Resolved 2 packages in [TIME]
-    Prepared 1 package in [TIME]
-    Installed 1 package in [TIME]
+    Prepared 2 packages in [TIME]
+    Installed 2 packages in [TIME]
+     + anyio==0.1.0 (from file://[TEMP_DIR]/)
      + typing-extensions==4.10.0
     ");
 
@@ -10389,7 +10390,10 @@ fn add_self() -> Result<()> {
 
     ----- stderr -----
     Resolved 2 packages in [TIME]
-    Audited 1 package in [TIME]
+    Prepared 1 package in [TIME]
+    Uninstalled 1 package in [TIME]
+    Installed 1 package in [TIME]
+     ~ anyio==0.1.0 (from file://[TEMP_DIR]/)
     ");
 
     let pyproject_toml = context.read("pyproject.toml");
@@ -13173,7 +13177,9 @@ fn add_path_with_existing_workspace() -> Result<()> {
     ----- stderr -----
     Added `dep` to workspace members
     Resolved 3 packages in [TIME]
-    Audited in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + dep==0.1.0 (from file://[TEMP_DIR]/dep)
     ");
 
     let pyproject_toml = context.read("pyproject.toml");
@@ -13250,7 +13256,9 @@ fn add_path_with_workspace() -> Result<()> {
     ----- stderr -----
     Added `dep` to workspace members
     Resolved 2 packages in [TIME]
-    Audited in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + dep==0.1.0 (from file://[TEMP_DIR]/dep)
     ");
 
     let pyproject_toml = context.read("pyproject.toml");
@@ -13316,7 +13324,9 @@ fn add_path_within_workspace_defaults_to_workspace() -> Result<()> {
     ----- stderr -----
     Added `dep` to workspace members
     Resolved 2 packages in [TIME]
-    Audited in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + dep==0.1.0 (from file://[TEMP_DIR]/dep)
     ");
 
     let pyproject_toml = context.read("pyproject.toml");