Remove workspace root for single-member workspace with uv export (#7254)

## Summary

If we have a single-member workspace, we actually don't write it to
`members`.

Closes https://github.com/astral-sh/uv/issues/7241.

crates/uv-configuration/src/install_options.rs

@@ -88,8 +88,9 @@ impl InstallOptions {
         project_name: &PackageName,
         members: &BTreeSet<PackageName>,
     ) -> bool {
-        // If `--no-install-project` is set, remove the project itself.
-        if self.no_install_project && package == project_name {
+        // If `--no-install-project` is set, remove the project itself. The project is always
+        // part of the workspace.
+        if (self.no_install_project || self.no_install_workspace) && package == project_name {
             return false;
         }
 

crates/uv/tests/export.rs

@@ -821,5 +821,41 @@ fn no_emit() -> Result<()> {
     Resolved 6 packages in [TIME]
     "###);
 
+    // Remove 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 = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42"]
+        build-backend = "setuptools.build_meta"
+        "#,
+    )?;
+
+    // Exclude the workspace.
+    uv_snapshot!(context.filters(), context.export().arg("--no-emit-workspace"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated via `uv export`.
+    anyio==3.7.0 \
+        --hash=sha256:275d9973793619a5374e1c89a4f4ad3f4b0a5510a2b5b939444bee8f4c4d37ce \
+        --hash=sha256:eddca883c4175f14df8aedce21054bfca3adb70ffe76a9f607aef9d7fa2ea7f0
+    idna==3.6 \
+        --hash=sha256:9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca \
+        --hash=sha256:c05567e9c24a6b9faaa835c4821bad0590fbb9d5779e7caa6e1cc4978e7eb24f
+    sniffio==1.3.1 \
+        --hash=sha256:f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc \
+        --hash=sha256:2f6da418d1f1e0fddd844478f41680e794e6051915791a034ff65e5f100525a2
+
+    ----- stderr -----
+    Resolved 4 packages in [TIME]
+    "###);
+
     Ok(())
 }