Fix --no-emit-workspace with --all-packages on single-member workspaces

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

@@ -95,7 +95,17 @@ impl<'lock> Installable<'lock> for InstallTarget<'lock> {
         match self {
             Self::Project { name, .. } => Some(name),
             Self::Projects { .. } => None,
-            Self::Workspace { .. } => None,
+            Self::Workspace { lock, .. } => {
+                // If the workspace contains a single member at the root, it will be omitted from
+                // the list of workspace members encoded in the lockfile. In that case, identify
+                // the root project by its source so that install options (e.g.,
+                // `--no-emit-workspace`) can filter it correctly.
+                if lock.members().is_empty() {
+                    lock.root().map(Package::name)
+                } else {
+                    None
+                }
+            }
             Self::NonProjectWorkspace { .. } => None,
             Self::Script { .. } => None,
         }

crates/uv/tests/it/export.rs

@@ -2265,6 +2265,56 @@ fn requirements_txt_no_emit() -> Result<()> {
     Ok(())
 }
 
+/// `--no-emit-workspace` should be respected when `--all-packages` is passed,
+/// even if the workspace has a single member (i.e., no additional packages).
+///
+/// See: <https://github.com/astral-sh/uv/issues/18070>
+#[test]
+fn requirements_txt_no_emit_workspace_all_packages() -> Result<()> {
+    let context = uv_test::test_context!("3.12");
+
+    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 = ["uv_build>=0.8.22,<10000"]
+        build-backend = "uv_build"
+        "#,
+    )?;
+
+    // `--no-emit-workspace --all-packages` on a single-member workspace should not emit `-e .`.
+    uv_snapshot!(context.filters(), context.export().arg("--no-emit-workspace").arg("--all-packages"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv export --cache-dir [CACHE_DIR] --no-emit-workspace --all-packages
+    anyio==3.7.0 \
+        --hash=sha256:275d9973793619a5374e1c89a4f4ad3f4b0a5510a2b5b939444bee8f4c4d37ce \
+        --hash=sha256:eddca883c4175f14df8aedce21054bfca3adb70ffe76a9f607aef9d7fa2ea7f0
+        # via project
+    idna==3.6 \
+        --hash=sha256:9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca \
+        --hash=sha256:c05567e9c24a6b9faaa835c4821bad0590fbb9d5779e7caa6e1cc4978e7eb24f
+        # via anyio
+    sniffio==1.3.1 \
+        --hash=sha256:2f6da418d1f1e0fddd844478f41680e794e6051915791a034ff65e5f100525a2 \
+        --hash=sha256:f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc
+        # via anyio
+
+    ----- stderr -----
+    Resolved 4 packages in [TIME]
+    ");
+
+    Ok(())
+}
+
 #[test]
 fn requirements_txt_only_emit() -> Result<()> {
     let context = uv_test::test_context!("3.12");