Warn when trying to uv sync a package without build configuration (#7420)

This enhances `uv sync` logic in order to detect and warn if it is
trying to operate on a packaged project with entrypoints.

Ref: #6998 (comment)
Closes: #7034

Author: lucab

crates/uv-workspace/src/pyproject.rs

@@ -44,7 +44,7 @@ pub struct PyProjectToml {
     #[serde(skip)]
     pub raw: String,
 
-    /// Used to determine whether a `build-system` is present.
+    /// Used to determine whether a `build-system` section is present.
     #[serde(default, skip_serializing)]
     build_system: Option<serde::de::IgnoredAny>,
 }
@@ -82,6 +82,15 @@ impl PyProjectToml {
         // Otherwise, a project is assumed to be a package if `build-system` is present.
         self.build_system.is_some()
     }
+
+    /// Returns whether the project manifest contains any script table.
+    pub fn has_scripts(&self) -> bool {
+        if let Some(ref project) = self.project {
+            project.gui_scripts.is_some() || project.scripts.is_some()
+        } else {
+            false
+        }
+    }
 }
 
 // Ignore raw document in comparison.
@@ -102,7 +111,7 @@ impl AsRef<[u8]> for PyProjectToml {
 /// PEP 621 project metadata (`project`).
 ///
 /// See <https://packaging.python.org/en/latest/specifications/pyproject-toml>.
-#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq)]
 #[serde(rename_all = "kebab-case")]
 pub struct Project {
     /// The name of the project
@@ -113,6 +122,13 @@ pub struct Project {
     pub requires_python: Option<VersionSpecifiers>,
     /// The optional dependencies of the project.
     pub optional_dependencies: Option<BTreeMap<ExtraName, Vec<String>>>,
+
+    /// Used to determine whether a `gui-scripts` section is present.
+    #[serde(default, skip_serializing)]
+    pub(crate) gui_scripts: Option<serde::de::IgnoredAny>,
+    /// Used to determine whether a `scripts` section is present.
+    #[serde(default, skip_serializing)]
+    pub(crate) scripts: Option<serde::de::IgnoredAny>,
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]

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

@@ -16,6 +16,7 @@ use uv_normalize::{PackageName, DEV_DEPENDENCIES};
 use uv_python::{PythonDownloads, PythonEnvironment, PythonPreference, PythonRequest};
 use uv_resolver::{FlatIndex, Lock};
 use uv_types::{BuildIsolation, HashStrategy};
+use uv_warnings::warn_user;
 use uv_workspace::{DiscoveryOptions, InstallTarget, MemberDiscovery, VirtualProject, Workspace};
 
 use crate::commands::pip::loggers::{DefaultInstallLogger, DefaultResolveLogger, InstallLogger};
@@ -74,6 +75,14 @@ pub(crate) async fn sync(
         InstallTarget::from(&project)
     };
 
+    // 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()
+    {
+        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`");
+    }
+
     // Discover or create the virtual environment.
     let venv = project::get_or_init_environment(
         target.workspace(),

crates/uv/tests/run.rs

@@ -1950,3 +1950,45 @@ fn run_invalid_project_table() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+#[cfg(target_family = "unix")]
+fn run_script_without_build_system() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(indoc! { r#"
+        [project]
+        name = "foo"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+
+        [project.scripts]
+        entry = "foo:custom_entry"
+        "#
+    })?;
+
+    let test_script = context.temp_dir.child("src/__init__.py");
+    test_script.write_str(indoc! { r#"
+        def custom_entry():
+            print!("Hello")
+       "#
+    })?;
+
+    // TODO(lucab): this should match `entry` and warn
+    // <https://github.com/astral-sh/uv/issues/7428>
+    uv_snapshot!(context.filters(), context.run().arg("entry"), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    Audited in [TIME]
+    error: Failed to spawn: `entry`
+      Caused by: No such file or directory (os error 2)
+    "###);
+
+    Ok(())
+}

crates/uv/tests/sync.rs

@@ -2328,3 +2328,94 @@ fn transitive_dev() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+/// Check warning message for <https://github.com/astral-sh/uv/issues/6998>
+/// if no `build-system` section is defined.
+fn sync_scripts_without_build_system() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "foo"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+
+        [project.scripts]
+        entry = "foo:custom_entry"
+        "#,
+    )?;
+
+    let test_script = context.temp_dir.child("src/__init__.py");
+    test_script.write_str(
+        r#"
+        def custom_entry():
+            print!("Hello")
+       "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.sync(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: 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`
+    Resolved 1 package in [TIME]
+    Audited in [TIME]
+    "###);
+
+    Ok(())
+}
+
+#[test]
+/// Check warning message for <https://github.com/astral-sh/uv/issues/6998>
+/// if the project is marked as `package = false`.
+fn sync_scripts_project_not_packaged() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "foo"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+
+        [project.scripts]
+        entry = "foo:custom_entry"
+
+        [build-system]
+        requires = ["hatchling"]
+        build-backend = "hatchling.build"
+
+        [tool.uv]
+        package = false
+        "#,
+    )?;
+
+    let test_script = context.temp_dir.child("src/__init__.py");
+    test_script.write_str(
+        r#"
+        def custom_entry():
+            print!("Hello")
+       "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.sync(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: 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`
+    Resolved 1 package in [TIME]
+    Audited in [TIME]
+    "###);
+
+    Ok(())
+}