Avoid including non-excluded members in parent workspaces (#6735)

## Summary

If you're in a directory, and there's workspace above it, we check if
the directory is excluded from the workspace members... But not if it's
_included_ in the first place.

Closes https://github.com/astral-sh/uv/issues/6732.

crates/uv-workspace/src/workspace.rs

@@ -1006,6 +1006,14 @@ async fn find_workspace(
             .and_then(|tool| tool.uv.as_ref())
             .and_then(|uv| uv.workspace.as_ref())
         {
+            if !is_included_in_workspace(project_root, workspace_root, workspace)? {
+                debug!(
+                    "Found workspace root `{}`, but project is not included",
+                    workspace_root.simplified_display()
+                );
+                return Ok(None);
+            }
+
             if is_excluded_from_workspace(project_root, workspace_root, workspace)? {
                 debug!(
                     "Found workspace root `{}`, but project is excluded",
@@ -1101,6 +1109,21 @@ pub fn check_nested_workspaces(inner_workspace_root: &Path, options: &DiscoveryO
             .and_then(|tool| tool.uv.as_ref())
             .and_then(|uv| uv.workspace.as_ref())
         {
+            let is_included = match is_included_in_workspace(
+                inner_workspace_root,
+                outer_workspace_root,
+                workspace,
+            ) {
+                Ok(contents) => contents,
+                Err(err) => {
+                    warn!(
+                        "Invalid pyproject.toml `{}`: {err}",
+                        pyproject_toml_path.simplified_display()
+                    );
+                    return;
+                }
+            };
+
             let is_excluded = match is_excluded_from_workspace(
                 inner_workspace_root,
                 outer_workspace_root,
@@ -1115,7 +1138,8 @@ pub fn check_nested_workspaces(inner_workspace_root: &Path, options: &DiscoveryO
                     return;
                 }
             };
-            if !is_excluded {
+
+            if is_included && !is_excluded {
                 warn_user!(
                     "Nested workspaces are not supported, but outer workspace (`{}`) includes `{}`",
                     outer_workspace_root.simplified_display().cyan(),

crates/uv/tests/workspace.rs

@@ -948,6 +948,66 @@ fn workspace_hidden_member() -> Result<()> {
     Ok(())
 }
 
+/// Ensure that workspace discovery accepts valid hidden directories.
+#[test]
+fn workspace_non_included_member() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    // Build the main workspace ...
+    let workspace = context.temp_dir.child("workspace");
+    workspace.child("pyproject.toml").write_str(indoc! {r#"
+        [tool.uv.workspace]
+        members = ["packages/*"]
+    "#})?;
+
+    // ... with a  ...
+    let deps = indoc! {r#"
+        dependencies = ["b"]
+
+        [tool.uv.sources]
+        b = { workspace = true }
+    "#};
+    make_project(&workspace.join("packages").join("a"), "a", deps)?;
+
+    // ... and b.
+    let deps = indoc! {r"
+        dependencies = []
+    "};
+    make_project(&workspace.join("packages").join("b"), "b", deps)?;
+
+    // ... and c, which is _not_ a member, but also isn't explicitly excluded.
+    let deps = indoc! {r"
+        dependencies = []
+    "};
+    make_project(&workspace.join("c"), "c", deps)?;
+
+    // Locking from `c` should not include any workspace members.
+    uv_snapshot!(context.filters(), context.lock().current_dir(workspace.join("c")), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Using Python 3.12.[X] interpreter at: [PYTHON-3.12]
+    Resolved 1 package in [TIME]
+    "###
+    );
+
+    let lock: SourceLock = toml::from_str(&fs_err::read_to_string(
+        workspace.join("c").join("uv.lock"),
+    )?)?;
+
+    assert_json_snapshot!(lock.sources(), @r###"
+    {
+      "c": {
+        "editable": "."
+      }
+    }
+    "###);
+
+    Ok(())
+}
+
 /// Ensure workspace members inherit sources from the root, if not specified in the member.
 ///
 /// In such cases, relative paths should be resolved relative to the workspace root, rather than