Build and install workspace members that are dependencies by default (#14663)

Regardless of the presence of a build system, as in
https://github.com/astral-sh/uv/pull/14413

---------

Co-authored-by: John Mumm <jtfmumm@gmail.com>

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

@@ -306,7 +306,10 @@ impl LoweredRequirement {
                                     },
                                     url,
                                 }
-                            } else if member.pyproject_toml().is_package() {
+                            } else if member
+                                .pyproject_toml()
+                                .is_package(!workspace.is_required_member(&requirement.name))
+                            {
                                 RequirementSource::Directory {
                                     install_path: install_path.into_boxed_path(),
                                     url,
@@ -736,7 +739,8 @@ 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-platform-tags/src/tags.rs

@@ -771,7 +771,7 @@ mod tests {
     /// A reference list can be generated with:
     /// ```text
     /// $ python -c "from packaging import tags; [print(tag) for tag in tags.platform_tags()]"`
-    /// ````
+    /// ```
     #[test]
     fn test_platform_tags_manylinux() {
         let tags = compatible_tags(&Platform::new(

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>>;
@@ -109,6 +109,8 @@ pub struct Workspace {
     install_path: PathBuf,
     /// The members of the workspace.
     packages: WorkspaceMembers,
+    /// The workspace members that are required by other members.
+    required_members: BTreeSet<PackageName>,
     /// The sources table from the workspace `pyproject.toml`.
     ///
     /// This table is overridden by the project sources.
@@ -260,6 +262,7 @@ 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 {
@@ -279,17 +282,33 @@ impl Workspace {
             // Set the `pyproject.toml` for the member.
             member.pyproject_toml = pyproject_toml;
 
+            // Recompute required_members with the updated data
+            let required_members = Self::collect_required_members(
+                &packages,
+                &workspace_sources,
+                &workspace_pyproject_toml,
+            );
+
             Some(Self {
                 pyproject_toml: workspace_pyproject_toml,
                 sources: workspace_sources,
                 packages,
+                required_members,
                 ..self
             })
         } else {
             // Set the `pyproject.toml` for the member.
             member.pyproject_toml = pyproject_toml;
 
-            Some(Self { packages, ..self })
+            // Recompute required_members with the updated member data
+            let required_members =
+                Self::collect_required_members(&packages, &self.sources, &self.pyproject_toml);
+
+            Some(Self {
+                packages,
+                required_members,
+                ..self
+            })
         }
     }
 
@@ -303,7 +322,7 @@ 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 +331,10 @@ 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 +354,65 @@ impl Workspace {
         })
     }
 
+    /// The workspace members that are required my another member of the workspace.
+    pub fn required_members(&self) -> &BTreeSet<PackageName> {
+        &self.required_members
+    }
+
+    /// Compute the workspace members that are required by another member of the workspace.
+    ///
+    /// N.B. this checks if a workspace member is required by inspecting `tool.uv.source` entries,
+    /// but does not actually check if the source is _used_, which could result in false positives
+    /// but is easier to compute.
+    fn collect_required_members(
+        packages: &BTreeMap<PackageName, WorkspaceMember>,
+        sources: &BTreeMap<PackageName, Sources>,
+        pyproject_toml: &PyProjectToml,
+    ) -> BTreeSet<PackageName> {
+        sources
+            .iter()
+            .filter(|(name, _)| {
+                pyproject_toml
+                    .project
+                    .as_ref()
+                    .is_none_or(|project| project.name != **name)
+            })
+            .chain(
+                packages
+                    .iter()
+                    .filter_map(|(name, member)| {
+                        member
+                            .pyproject_toml
+                            .tool
+                            .as_ref()
+                            .and_then(|tool| tool.uv.as_ref())
+                            .and_then(|uv| uv.sources.as_ref())
+                            .map(ToolUvSources::inner)
+                            .map(move |sources| {
+                                sources
+                                    .iter()
+                                    .filter(move |(source_name, _)| name != *source_name)
+                            })
+                    })
+                    .flatten(),
+            )
+            .filter_map(|(package, sources)| {
+                sources
+                    .iter()
+                    .any(|source| matches!(source, Source::Workspace { .. }))
+                    .then_some(package.clone())
+            })
+            .collect()
+    }
+
+    /// Whether a given workspace member is required by another member.
+    pub fn is_required_member(&self, name: &PackageName) -> bool {
+        self.required_members().contains(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 +446,10 @@ 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),
@@ -746,9 +827,16 @@ impl Workspace {
             .and_then(|uv| uv.index)
             .unwrap_or_default();
 
+        let required_members = Self::collect_required_members(
+            &workspace_members,
+            &workspace_sources,
+            &workspace_pyproject_toml,
+        );
+
         Ok(Workspace {
             install_path: workspace_root,
             packages: workspace_members,
+            required_members,
             sources: workspace_sources,
             indexes: workspace_indexes,
             pyproject_toml: workspace_pyproject_toml,
@@ -1232,15 +1320,23 @@ impl ProjectWorkspace {
                 project.name.clone(),
                 current_project,
             )]));
+            let workspace_sources = BTreeMap::default();
+            let required_members = Workspace::collect_required_members(
+                &current_project_as_members,
+                &workspace_sources,
+                project_pyproject_toml,
+            );
+
             return Ok(Self {
                 project_root: project_path.clone(),
                 project_name: project.name.clone(),
                 workspace: Workspace {
                     install_path: project_path.clone(),
                     packages: current_project_as_members,
+                    required_members,
                     // There may be package sources, but we don't need to duplicate them into the
                     // workspace sources.
-                    sources: BTreeMap::default(),
+                    sources: workspace_sources,
                     indexes: Vec::default(),
                     pyproject_toml: project_pyproject_toml.clone(),
                 },
@@ -1692,6 +1788,7 @@ mod tests {
                 "pyproject_toml": "[PYPROJECT_TOML]"
               }
             },
+            "required_members": [],
             "sources": {},
             "indexes": [],
             "pyproject_toml": {
@@ -1745,6 +1842,7 @@ mod tests {
                     "pyproject_toml": "[PYPROJECT_TOML]"
                   }
                 },
+                "required_members": [],
                 "sources": {},
                 "indexes": [],
                 "pyproject_toml": {
@@ -1825,6 +1923,10 @@ mod tests {
                     "pyproject_toml": "[PYPROJECT_TOML]"
                   }
                 },
+                "required_members": [
+                  "bird-feeder",
+                  "seeds"
+                ],
                 "sources": {
                   "bird-feeder": [
                     {
@@ -1946,6 +2048,10 @@ mod tests {
                     "pyproject_toml": "[PYPROJECT_TOML]"
                   }
                 },
+                "required_members": [
+                  "bird-feeder",
+                  "seeds"
+                ],
                 "sources": {},
                 "indexes": [],
                 "pyproject_toml": {
@@ -2013,6 +2119,7 @@ mod tests {
                     "pyproject_toml": "[PYPROJECT_TOML]"
                   }
                 },
+                "required_members": [],
                 "sources": {},
                 "indexes": [],
                 "pyproject_toml": {
@@ -2147,6 +2254,7 @@ mod tests {
                     "pyproject_toml": "[PYPROJECT_TOML]"
                   }
                 },
+                "required_members": [],
                 "sources": {},
                 "indexes": [],
                 "pyproject_toml": {
@@ -2254,6 +2362,7 @@ mod tests {
                     "pyproject_toml": "[PYPROJECT_TOML]"
                   }
                 },
+                "required_members": [],
                 "sources": {},
                 "indexes": [],
                 "pyproject_toml": {
@@ -2375,6 +2484,7 @@ mod tests {
                     "pyproject_toml": "[PYPROJECT_TOML]"
                   }
                 },
+                "required_members": [],
                 "sources": {},
                 "indexes": [],
                 "pyproject_toml": {
@@ -2470,6 +2580,7 @@ mod tests {
                     "pyproject_toml": "[PYPROJECT_TOML]"
                   }
                 },
+                "required_members": [],
                 "sources": {},
                 "indexes": [],
                 "pyproject_toml": {

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) -> &'lock BTreeSet<PackageName> {
+        match self {
+            Self::Workspace(workspace) => workspace.required_members(),
+            Self::Script(_) => {
+                static EMPTY: BTreeSet<PackageName> = BTreeSet::new();
+                &EMPTY
+            }
+        }
+    }
+
     /// 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

@@ -10362,7 +10362,7 @@ fn add_self() -> Result<()> {
         filters => context.filters(),
     }, {
         assert_snapshot!(
-            pyproject_toml, @r###"
+            pyproject_toml, @r#"
         [project]
         name = "anyio"
         version = "0.1.0"
@@ -10377,7 +10377,7 @@ fn add_self() -> Result<()> {
 
         [tool.uv.sources]
         anyio = { workspace = true }
-        "###
+        "#
         );
     });
 
@@ -10398,7 +10398,7 @@ fn add_self() -> Result<()> {
         filters => context.filters(),
     }, {
         assert_snapshot!(
-            pyproject_toml, @r###"
+            pyproject_toml, @r#"
         [project]
         name = "anyio"
         version = "0.1.0"
@@ -10418,7 +10418,7 @@ fn add_self() -> Result<()> {
         dev = [
             "anyio[types]",
         ]
-        "###
+        "#
         );
     });
 
@@ -13173,7 +13173,9 @@ 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 +13252,9 @@ 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 +13320,9 @@ 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");

crates/uv/tests/it/lock.rs

@@ -12064,10 +12064,6 @@ fn lock_remove_member() -> Result<()> {
         requires-python = ">=3.12"
         dependencies = ["leaf"]
 
-        [build-system]
-        requires = ["setuptools>=42"]
-        build-backend = "setuptools.build_meta"
-
         [tool.uv.workspace]
         members = ["leaf"]
 
@@ -12130,7 +12126,7 @@ fn lock_remove_member() -> Result<()> {
         [[package]]
         name = "leaf"
         version = "0.1.0"
-        source = { virtual = "leaf" }
+        source = { editable = "leaf" }
         dependencies = [
             { name = "anyio" },
         ]
@@ -12141,13 +12137,13 @@ fn lock_remove_member() -> Result<()> {
         [[package]]
         name = "project"
         version = "0.1.0"
-        source = { editable = "." }
+        source = { virtual = "." }
         dependencies = [
             { name = "leaf" },
         ]
 
         [package.metadata]
-        requires-dist = [{ name = "leaf", virtual = "leaf" }]
+        requires-dist = [{ name = "leaf", editable = "leaf" }]
 
         [[package]]
         name = "sniffio"
@@ -12162,16 +12158,124 @@ fn lock_remove_member() -> Result<()> {
     });
 
     // Re-run with `--locked`.
-    uv_snapshot!(context.filters(), context.lock().arg("--locked"), @r###"
+    uv_snapshot!(context.filters(), context.lock().arg("--locked"), @r"
     success: true
     exit_code: 0
     ----- stdout -----
 
     ----- stderr -----
     Resolved 5 packages in [TIME]
-    "###);
+    ");
 
-    // Remove the member.
+    // Remove the member as a dependency (retain it as a workspace member)
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+
+        [tool.uv.workspace]
+        members = ["leaf"]
+
+        [tool.uv.sources]
+        leaf = { workspace = true }
+        "#,
+    )?;
+
+    // Re-run with `--locked`. This should fail.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked"), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 5 packages in [TIME]
+    The lockfile at `uv.lock` needs to be updated, but `--locked` was provided. To update the lockfile, run `uv lock`.
+    ");
+
+    // Re-run without `--locked`.
+    uv_snapshot!(context.filters(), context.lock(), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 5 packages in [TIME]
+    ");
+
+    let lock = context.read("uv.lock");
+
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            lock, @r#"
+        version = 1
+        revision = 2
+        requires-python = ">=3.12"
+
+        [options]
+        exclude-newer = "2024-03-25T00:00:00Z"
+
+        [manifest]
+        members = [
+            "leaf",
+            "project",
+        ]
+
+        [[package]]
+        name = "anyio"
+        version = "4.3.0"
+        source = { registry = "https://pypi.org/simple" }
+        dependencies = [
+            { name = "idna" },
+            { name = "sniffio" },
+        ]
+        sdist = { url = "https://files.pythonhosted.org/packages/db/4d/3970183622f0330d3c23d9b8a5f52e365e50381fd484d08e3285104333d3/anyio-4.3.0.tar.gz", hash = "sha256:f75253795a87df48568485fd18cdd2a3fa5c4f7c5be8e5e36637733fce06fed6", size = 159642, upload-time = "2024-02-19T08:36:28.641Z" }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/14/fd/2f20c40b45e4fb4324834aea24bd4afdf1143390242c0b33774da0e2e34f/anyio-4.3.0-py3-none-any.whl", hash = "sha256:048e05d0f6caeed70d731f3db756d35dcc1f35747c8c403364a8332c630441b8", size = 85584, upload-time = "2024-02-19T08:36:26.842Z" },
+        ]
+
+        [[package]]
+        name = "idna"
+        version = "3.6"
+        source = { registry = "https://pypi.org/simple" }
+        sdist = { url = "https://files.pythonhosted.org/packages/bf/3f/ea4b9117521a1e9c50344b909be7886dd00a519552724809bb1f486986c2/idna-3.6.tar.gz", hash = "sha256:9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca", size = 175426, upload-time = "2023-11-25T15:40:54.902Z" }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/c2/e7/a82b05cf63a603df6e68d59ae6a68bf5064484a0718ea5033660af4b54a9/idna-3.6-py3-none-any.whl", hash = "sha256:c05567e9c24a6b9faaa835c4821bad0590fbb9d5779e7caa6e1cc4978e7eb24f", size = 61567, upload-time = "2023-11-25T15:40:52.604Z" },
+        ]
+
+        [[package]]
+        name = "leaf"
+        version = "0.1.0"
+        source = { editable = "leaf" }
+        dependencies = [
+            { name = "anyio" },
+        ]
+
+        [package.metadata]
+        requires-dist = [{ name = "anyio", specifier = ">3" }]
+
+        [[package]]
+        name = "project"
+        version = "0.1.0"
+        source = { virtual = "." }
+
+        [[package]]
+        name = "sniffio"
+        version = "1.3.1"
+        source = { registry = "https://pypi.org/simple" }
+        sdist = { url = "https://files.pythonhosted.org/packages/a2/87/a6771e1546d97e7e041b6ae58d80074f81b7d5121207425c964ddf5cfdbd/sniffio-1.3.1.tar.gz", hash = "sha256:f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc", size = 20372, upload-time = "2024-02-25T23:20:04.057Z" }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/e9/44/75a9c9421471a6c4805dbf2356f7c181a29c1879239abab1ea2cc8f38b40/sniffio-1.3.1-py3-none-any.whl", hash = "sha256:2f6da418d1f1e0fddd844478f41680e794e6051915791a034ff65e5f100525a2", size = 10235, upload-time = "2024-02-25T23:20:01.196Z" },
+        ]
+        "#
+        );
+    });
+
+    // Remove the member entirely
     pyproject_toml.write_str(
         r#"
         [project]
@@ -12238,7 +12342,7 @@ fn lock_remove_member() -> Result<()> {
 /// This test would fail if we didn't write the list of workspace members to the lockfile, since
 /// we wouldn't be able to determine that a new member was added.
 #[test]
-fn lock_add_member() -> Result<()> {
+fn lock_add_member_with_build_system() -> Result<()> {
     let context = TestContext::new("3.12");
 
     // Create a workspace, but don't add the member.
@@ -12449,6 +12553,339 @@ fn lock_add_member() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn lock_add_member_without_build_system() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    // Create a workspace, but don't add the member.
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+
+        [tool.uv.workspace]
+        members = []
+        "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.lock(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    "###);
+
+    let lock = context.read("uv.lock");
+
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            lock, @r#"
+        version = 1
+        revision = 2
+        requires-python = ">=3.12"
+
+        [options]
+        exclude-newer = "2024-03-25T00:00:00Z"
+
+        [[package]]
+        name = "project"
+        version = "0.1.0"
+        source = { virtual = "." }
+        "#
+        );
+    });
+
+    // Re-run with `--locked`.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    "###);
+
+    // Create a workspace member.
+    let leaf = context.temp_dir.child("leaf");
+    leaf.child("pyproject.toml").write_str(
+        r#"
+        [project]
+        name = "leaf"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["anyio>3"]
+        "#,
+    )?;
+
+    // Add the member to the workspace, but not as a dependency of the root.
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+
+        [tool.uv.workspace]
+        members = ["leaf"]
+        "#,
+    )?;
+
+    // Re-run with `--locked`. This should fail.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked"), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 5 packages in [TIME]
+    The lockfile at `uv.lock` needs to be updated, but `--locked` was provided. To update the lockfile, run `uv lock`.
+    ");
+
+    // Re-run with `--offline`. This should also fail, during the resolve phase.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked").arg("--offline").arg("--no-cache"), @r###"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+      × No solution found when resolving dependencies:
+      ╰─▶ Because anyio was not found in the cache and leaf depends on anyio>3, we can conclude that leaf's requirements are unsatisfiable.
+          And because your workspace requires leaf, we can conclude that your workspace's requirements are unsatisfiable.
+
+          hint: Packages were unavailable because the network was disabled. When the network is disabled, registry packages may only be read from the cache.
+    "###);
+
+    // Re-run without `--locked`.
+    uv_snapshot!(context.filters(), context.lock(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 5 packages in [TIME]
+    Added anyio v4.3.0
+    Added idna v3.6
+    Added leaf v0.1.0
+    Added sniffio v1.3.1
+    "###);
+
+    // Re-run with `--locked`.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 5 packages in [TIME]
+    "###);
+
+    let lock = context.read("uv.lock");
+
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            lock, @r#"
+        version = 1
+        revision = 2
+        requires-python = ">=3.12"
+
+        [options]
+        exclude-newer = "2024-03-25T00:00:00Z"
+
+        [manifest]
+        members = [
+            "leaf",
+            "project",
+        ]
+
+        [[package]]
+        name = "anyio"
+        version = "4.3.0"
+        source = { registry = "https://pypi.org/simple" }
+        dependencies = [
+            { name = "idna" },
+            { name = "sniffio" },
+        ]
+        sdist = { url = "https://files.pythonhosted.org/packages/db/4d/3970183622f0330d3c23d9b8a5f52e365e50381fd484d08e3285104333d3/anyio-4.3.0.tar.gz", hash = "sha256:f75253795a87df48568485fd18cdd2a3fa5c4f7c5be8e5e36637733fce06fed6", size = 159642, upload-time = "2024-02-19T08:36:28.641Z" }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/14/fd/2f20c40b45e4fb4324834aea24bd4afdf1143390242c0b33774da0e2e34f/anyio-4.3.0-py3-none-any.whl", hash = "sha256:048e05d0f6caeed70d731f3db756d35dcc1f35747c8c403364a8332c630441b8", size = 85584, upload-time = "2024-02-19T08:36:26.842Z" },
+        ]
+
+        [[package]]
+        name = "idna"
+        version = "3.6"
+        source = { registry = "https://pypi.org/simple" }
+        sdist = { url = "https://files.pythonhosted.org/packages/bf/3f/ea4b9117521a1e9c50344b909be7886dd00a519552724809bb1f486986c2/idna-3.6.tar.gz", hash = "sha256:9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca", size = 175426, upload-time = "2023-11-25T15:40:54.902Z" }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/c2/e7/a82b05cf63a603df6e68d59ae6a68bf5064484a0718ea5033660af4b54a9/idna-3.6-py3-none-any.whl", hash = "sha256:c05567e9c24a6b9faaa835c4821bad0590fbb9d5779e7caa6e1cc4978e7eb24f", size = 61567, upload-time = "2023-11-25T15:40:52.604Z" },
+        ]
+
+        [[package]]
+        name = "leaf"
+        version = "0.1.0"
+        source = { virtual = "leaf" }
+        dependencies = [
+            { name = "anyio" },
+        ]
+
+        [package.metadata]
+        requires-dist = [{ name = "anyio", specifier = ">3" }]
+
+        [[package]]
+        name = "project"
+        version = "0.1.0"
+        source = { virtual = "." }
+
+        [[package]]
+        name = "sniffio"
+        version = "1.3.1"
+        source = { registry = "https://pypi.org/simple" }
+        sdist = { url = "https://files.pythonhosted.org/packages/a2/87/a6771e1546d97e7e041b6ae58d80074f81b7d5121207425c964ddf5cfdbd/sniffio-1.3.1.tar.gz", hash = "sha256:f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc", size = 20372, upload-time = "2024-02-25T23:20:04.057Z" }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/e9/44/75a9c9421471a6c4805dbf2356f7c181a29c1879239abab1ea2cc8f38b40/sniffio-1.3.1-py3-none-any.whl", hash = "sha256:2f6da418d1f1e0fddd844478f41680e794e6051915791a034ff65e5f100525a2", size = 10235, upload-time = "2024-02-25T23:20:01.196Z" },
+        ]
+        "#
+        );
+    });
+
+    // Add the member to the workspace, as a dependency of the root.
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["leaf"]
+
+        [tool.uv.workspace]
+        members = ["leaf"]
+
+        [tool.uv.sources]
+        leaf = { workspace = true }
+        "#,
+    )?;
+
+    // Re-run with `--locked`. This should fail.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked"), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 5 packages in [TIME]
+    The lockfile at `uv.lock` needs to be updated, but `--locked` was provided. To update the lockfile, run `uv lock`.
+    ");
+
+    // Re-run without `--locked`.
+    uv_snapshot!(context.filters(), context.lock(), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 5 packages in [TIME]
+    ");
+
+    // Re-run with `--locked`.
+    uv_snapshot!(context.filters(), context.lock().arg("--locked"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 5 packages in [TIME]
+    ");
+
+    let lock = context.read("uv.lock");
+
+    // It should change from a virtual to an editable source
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            lock, @r#"
+        version = 1
+        revision = 2
+        requires-python = ">=3.12"
+
+        [options]
+        exclude-newer = "2024-03-25T00:00:00Z"
+
+        [manifest]
+        members = [
+            "leaf",
+            "project",
+        ]
+
+        [[package]]
+        name = "anyio"
+        version = "4.3.0"
+        source = { registry = "https://pypi.org/simple" }
+        dependencies = [
+            { name = "idna" },
+            { name = "sniffio" },
+        ]
+        sdist = { url = "https://files.pythonhosted.org/packages/db/4d/3970183622f0330d3c23d9b8a5f52e365e50381fd484d08e3285104333d3/anyio-4.3.0.tar.gz", hash = "sha256:f75253795a87df48568485fd18cdd2a3fa5c4f7c5be8e5e36637733fce06fed6", size = 159642, upload-time = "2024-02-19T08:36:28.641Z" }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/14/fd/2f20c40b45e4fb4324834aea24bd4afdf1143390242c0b33774da0e2e34f/anyio-4.3.0-py3-none-any.whl", hash = "sha256:048e05d0f6caeed70d731f3db756d35dcc1f35747c8c403364a8332c630441b8", size = 85584, upload-time = "2024-02-19T08:36:26.842Z" },
+        ]
+
+        [[package]]
+        name = "idna"
+        version = "3.6"
+        source = { registry = "https://pypi.org/simple" }
+        sdist = { url = "https://files.pythonhosted.org/packages/bf/3f/ea4b9117521a1e9c50344b909be7886dd00a519552724809bb1f486986c2/idna-3.6.tar.gz", hash = "sha256:9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca", size = 175426, upload-time = "2023-11-25T15:40:54.902Z" }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/c2/e7/a82b05cf63a603df6e68d59ae6a68bf5064484a0718ea5033660af4b54a9/idna-3.6-py3-none-any.whl", hash = "sha256:c05567e9c24a6b9faaa835c4821bad0590fbb9d5779e7caa6e1cc4978e7eb24f", size = 61567, upload-time = "2023-11-25T15:40:52.604Z" },
+        ]
+
+        [[package]]
+        name = "leaf"
+        version = "0.1.0"
+        source = { editable = "leaf" }
+        dependencies = [
+            { name = "anyio" },
+        ]
+
+        [package.metadata]
+        requires-dist = [{ name = "anyio", specifier = ">3" }]
+
+        [[package]]
+        name = "project"
+        version = "0.1.0"
+        source = { virtual = "." }
+        dependencies = [
+            { name = "leaf" },
+        ]
+
+        [package.metadata]
+        requires-dist = [{ name = "leaf", editable = "leaf" }]
+
+        [[package]]
+        name = "sniffio"
+        version = "1.3.1"
+        source = { registry = "https://pypi.org/simple" }
+        sdist = { url = "https://files.pythonhosted.org/packages/a2/87/a6771e1546d97e7e041b6ae58d80074f81b7d5121207425c964ddf5cfdbd/sniffio-1.3.1.tar.gz", hash = "sha256:f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc", size = 20372, upload-time = "2024-02-25T23:20:04.057Z" }
+        wheels = [
+            { url = "https://files.pythonhosted.org/packages/e9/44/75a9c9421471a6c4805dbf2356f7c181a29c1879239abab1ea2cc8f38b40/sniffio-1.3.1-py3-none-any.whl", hash = "sha256:2f6da418d1f1e0fddd844478f41680e794e6051915791a034ff65e5f100525a2", size = 10235, upload-time = "2024-02-25T23:20:01.196Z" },
+        ]
+        "#
+        );
+    });
+
+    Ok(())
+}
+
 /// Lock a `pyproject.toml`, then add a dependency that's already included in the resolution.
 /// In theory, we shouldn't need to re-resolve, but based on our current strategy, we don't accept
 /// the existing lockfile.

crates/uv/tests/it/lock_conflict.rs

@@ -1094,18 +1094,19 @@ fn extra_unconditional() -> Result<()> {
     "###);
     // This is fine because we are only enabling one
     // extra, and thus, there is no conflict.
-    uv_snapshot!(context.filters(), context.sync().arg("--frozen"), @r###"
+    uv_snapshot!(context.filters(), context.sync().arg("--frozen"), @r"
     success: true
     exit_code: 0
     ----- stdout -----
 
     ----- stderr -----
-    Prepared 3 packages in [TIME]
+    Prepared 4 packages in [TIME]
-    Installed 3 packages in [TIME]
+    Installed 4 packages in [TIME]
      + anyio==4.1.0
      + idna==3.6
+     + proxy1==0.1.0 (from file://[TEMP_DIR]/proxy1)
      + sniffio==1.3.1
-    "###);
+    ");
 
     // And same thing for the other extra.
     root_pyproject_toml.write_str(
@@ -1215,18 +1216,19 @@ fn extra_unconditional_non_conflicting() -> Result<()> {
     // `uv sync` wasn't correctly propagating extras in a way
     // that would satisfy the conflict markers that got added
     // to the `proxy1[extra1]` dependency.
-    uv_snapshot!(context.filters(), context.sync().arg("--frozen"), @r###"
+    uv_snapshot!(context.filters(), context.sync().arg("--frozen"), @r"
     success: true
     exit_code: 0
     ----- stdout -----
 
     ----- stderr -----
-    Prepared 3 packages in [TIME]
+    Prepared 4 packages in [TIME]
-    Installed 3 packages in [TIME]
+    Installed 4 packages in [TIME]
      + anyio==4.1.0
      + idna==3.6
+     + proxy1==0.1.0 (from file://[TEMP_DIR]/proxy1)
      + sniffio==1.3.1
-    "###);
+    ");
 
     Ok(())
 }
@@ -1301,16 +1303,17 @@ fn extra_unconditional_in_optional() -> Result<()> {
     "###);
 
     // This should install `sortedcontainers==2.3.0`.
-    uv_snapshot!(context.filters(), context.sync().arg("--frozen").arg("--extra=x1"), @r###"
+    uv_snapshot!(context.filters(), context.sync().arg("--frozen").arg("--extra=x1"), @r"
     success: true
     exit_code: 0
     ----- stdout -----
 
     ----- stderr -----
-    Prepared 1 package in [TIME]
+    Prepared 2 packages in [TIME]
-    Installed 1 package in [TIME]
+    Installed 2 packages in [TIME]
+     + proxy1==0.1.0 (from file://[TEMP_DIR]/proxy1)
      + sortedcontainers==2.3.0
-    "###);
+    ");
 
     // This should install `sortedcontainers==2.4.0`.
     uv_snapshot!(context.filters(), context.sync().arg("--frozen").arg("--extra=x2"), @r###"
@@ -4460,19 +4463,20 @@ conflicts = [
     error: Extra `x2` is not defined in the project's `optional-dependencies` table
     "###);
 
-    uv_snapshot!(context.filters(), context.sync(), @r###"
+    uv_snapshot!(context.filters(), context.sync(), @r"
     success: true
     exit_code: 0
     ----- stdout -----
 
     ----- stderr -----
     Resolved 7 packages in [TIME]
-    Prepared 3 packages in [TIME]
+    Prepared 4 packages in [TIME]
-    Installed 3 packages in [TIME]
+    Installed 4 packages in [TIME]
      + anyio==4.3.0
      + idna==3.6
+     + proxy1==0.1.0 (from file://[TEMP_DIR]/proxy1)
      + sniffio==1.3.1
-    "###);
+    ");
 
     let lock = fs_err::read_to_string(context.temp_dir.join("uv.lock")).unwrap();
     insta::with_settings!({
@@ -4558,14 +4562,14 @@ conflicts = [
         requires-dist = [
             { name = "anyio", specifier = ">=4" },
             { name = "idna", marker = "extra == 'x1'", specifier = "==3.6" },
-            { name = "proxy1", virtual = "proxy1" },
+            { name = "proxy1", editable = "proxy1" },
         ]
         provides-extras = ["x1"]
 
         [[package]]
         name = "proxy1"
         version = "0.1.0"
-        source = { virtual = "proxy1" }
+        source = { editable = "proxy1" }
 
         [package.optional-dependencies]
         x2 = [

crates/uv/tests/it/pip_compile.rs

@@ -15772,18 +15772,18 @@ fn project_and_group_workspace_inherit() -> Result<()> {
     ----- stdout -----
     # This file was autogenerated by uv via the following command:
     #    uv pip compile --cache-dir [CACHE_DIR] --group packages/mysubproject/pyproject.toml:foo
+    -e file://[TEMP_DIR]/packages/pytest
+        # via mysubproject (packages/mysubproject/pyproject.toml:foo)
+    -e file://[TEMP_DIR]/packages/sniffio
+        # via
+        #   mysubproject (packages/mysubproject/pyproject.toml:foo)
+        #   anyio
     anyio==4.3.0
         # via mysubproject (packages/mysubproject/pyproject.toml:foo)
     idna==3.6
         # via anyio
     iniconfig==2.0.0
         # via mysubproject (packages/mysubproject/pyproject.toml:foo)
-    pytest @ file://[TEMP_DIR]/packages/pytest
-        # via mysubproject (packages/mysubproject/pyproject.toml:foo)
-    sniffio @ file://[TEMP_DIR]/packages/sniffio
-        # via
-        #   mysubproject (packages/mysubproject/pyproject.toml:foo)
-        #   anyio
 
     ----- stderr -----
     Resolved 5 packages in [TIME]

crates/uv/tests/it/sync.rs

@@ -3565,6 +3565,101 @@ fn sync_ignore_extras_check_when_no_provides_extras() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn sync_workspace_members_with_transitive_dependencies() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [tool.uv.workspace]
+        members = [
+            "packages/*",
+        ]
+        "#,
+    )?;
+
+    let packages = context.temp_dir.child("packages");
+    packages.create_dir_all()?;
+
+    // Create three workspace members with transitive dependency from
+    // pkg-c -> pkg-b -> pkg-a
+    let pkg_a = packages.child("pkg-a");
+    pkg_a.create_dir_all()?;
+    let pkg_a_pyproject_toml = pkg_a.child("pyproject.toml");
+    pkg_a_pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "pkg-a"
+        version = "0.0.1"
+        requires-python = ">=3.12"
+        dependencies = ["anyio"]
+        "#,
+    )?;
+
+    let pkg_b = packages.child("pkg-b");
+    pkg_b.create_dir_all()?;
+    let pkg_b_pyproject_toml = pkg_b.child("pyproject.toml");
+    pkg_b_pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "pkg-b"
+        version = "0.0.1"
+        requires-python = ">=3.12"
+        dependencies = ["pkg-a"]
+
+        [tool.uv.sources]
+        pkg-a = { workspace = true }
+        "#,
+    )?;
+
+    let pkg_c = packages.child("pkg-c");
+    pkg_c.create_dir_all()?;
+    let pkg_c_pyproject_toml = pkg_c.child("pyproject.toml");
+    pkg_c_pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "pkg-c"
+        version = "0.0.1"
+        requires-python = ">=3.12"
+        dependencies = ["pkg-b"]
+
+        [tool.uv.sources]
+        pkg-b = { workspace = true }
+        "#,
+    )?;
+
+    // Syncing should build the two transitive dependencies pkg-a and pkg-b,
+    // but not pkg-c, which is not a dependency.
+    uv_snapshot!(context.filters(), context.sync(), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 6 packages in [TIME]
+    Prepared 5 packages in [TIME]
+    Installed 5 packages in [TIME]
+     + anyio==4.3.0
+     + idna==3.6
+     + pkg-a==0.0.1 (from file://[TEMP_DIR]/packages/pkg-a)
+     + pkg-b==0.0.1 (from file://[TEMP_DIR]/packages/pkg-b)
+     + sniffio==1.3.1
+    ");
+
+    // The lockfile should be valid.
+    uv_snapshot!(context.filters(), context.lock().arg("--check"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 6 packages in [TIME]
+    ");
+
+    Ok(())
+}
+
 #[test]
 fn sync_non_existent_extra_workspace_member() -> Result<()> {
     let context = TestContext::new("3.12");
@@ -3626,9 +3721,10 @@ fn sync_non_existent_extra_workspace_member() -> Result<()> {
 
     ----- stderr -----
     Resolved 5 packages in [TIME]
-    Prepared 3 packages in [TIME]
+    Prepared 4 packages in [TIME]
-    Installed 3 packages in [TIME]
+    Installed 4 packages in [TIME]
      + anyio==4.3.0
+     + child==0.1.0 (from file://[TEMP_DIR]/child)
      + idna==3.6
      + sniffio==1.3.1
     ");

docs/concepts/projects/dependencies.md

@@ -808,9 +808,9 @@ $ uv add --no-editable ./path/foo
 uv allows dependencies to be "virtual", in which the dependency itself is not installed as a
 [package](./config.md#project-packaging), but its dependencies are.
 
-By default, only workspace members without build systems declared are virtual.
+By default, dependencies are never virtual.
 
-A dependency with a [`path` source](#path) is not virtual unless it explicitly sets
+A dependency with a [`path` source](#path) can be virtual if it explicitly sets
 [`tool.uv.package = false`](../../reference/settings.md#package). Unlike working _in_ the dependent
 project with uv, the package will be built even if a [build system](./config.md#build-systems) is
 not declared.
@@ -825,8 +825,8 @@ dependencies = ["bar"]
 bar = { path = "../projects/bar", package = false }
 ```
 
-Similarly, if a dependency sets `tool.uv.package = false`, it can be overridden by declaring
+If a dependency sets `tool.uv.package = false`, it can be overridden by declaring `package = true`
-`package = true` on the source:
+on the source:
 
 ```toml title="pyproject.toml"
 [project]
@@ -836,6 +836,52 @@ dependencies = ["bar"]
 bar = { path = "../projects/bar", package = true }
 ```
 
+Similarly, a dependency with a [`workspace` source](#workspace-member) can be virtual if it
+explicitly sets [`tool.uv.package = false`](../../reference/settings.md#package). The workspace
+member will be built even if a [build system](./config.md#build-systems) is not declared.
+
+Workspace members that are _not_ dependencies can be virtual by default, e.g., if the parent
+`pyproject.toml` is:
+
+```toml title="pyproject.toml"
+[project]
+name = "parent"
+version = "1.0.0"
+dependencies = []
+
+[tool.uv.workspace]
+members = ["child"]
+```
+
+And the child `pyproject.toml` excluded a build system:
+
+```toml title="pyproject.toml"
+[project]
+name = "child"
+version = "1.0.0"
+dependencies = ["anyio"]
+```
+
+Then the `child` workspace member would not be installed, but the transitive dependency `anyio`
+would be.
+
+In contrast, if the parent declared a dependency on `child`:
+
+```toml title="pyproject.toml"
+[project]
+name = "parent"
+version = "1.0.0"
+dependencies = ["child"]
+
+[tool.uv.sources]
+child = { workspace = true }
+
+[tool.uv.workspace]
+members = ["child"]
+```
+
+Then `child` would be built and installed.
+
 ## Dependency specifiers
 
 uv uses standard