Add warning when dependencies are empty with Poetry metadata

crates/uv/src/requirements.rs

@@ -15,6 +15,8 @@ use uv_normalize::{ExtraName, PackageName};
 
 use crate::confirm;
 
+use uv_warnings::warn_user;
+
 #[derive(Debug)]
 pub(crate) enum RequirementsSource {
     /// A package was provided on the command line (e.g., `pip install flask`).
@@ -234,6 +236,17 @@ impl RequirementsSpecification {
                     })?);
                 }
 
+                if requirements.is_empty() {
+                    if pyproject_toml.build_system.is_some_and(|build_system| {
+                        build_system
+                            .requires
+                            .iter()
+                            .any(|v| v.name.as_dist_info_name().starts_with("poetry"))
+                    }) {
+                        warn_user!("`{}` does not contain any dependencies (hint: Poetry's format is not supported for now)", path.normalized_display());
+                    }
+                }
+
                 Self {
                     project: project_name,
                     requirements,

crates/uv/tests/pip_compile.rs

@@ -377,6 +377,46 @@ optional-dependencies.foo = [
     Ok(())
 }
 
+/// Show a dedicated warning if the user tries to compile a `pyproject.toml` file with a `poetry`
+/// section.
+#[test]
+fn compile_empty_pyproject_toml_poetry() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"[tool.poetry]
+name = "poetry-editable"
+version = "0.1.0"
+description = ""
+authors = ["Astral Software Inc. <hey@astral.sh>"]
+
+[tool.poetry.dependencies]
+python = "^3.10"
+numpy = "^1"
+
+[build-system]
+requires = ["poetry-core"]
+build-backend = "poetry.core.masonry.api"
+"#,
+    )?;
+
+    uv_snapshot!(context.compile()
+            .arg("pyproject.toml"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv v[VERSION] via the following command:
+    #    uv pip compile --cache-dir [CACHE_DIR] --exclude-newer 2023-11-18T12:00:00Z pyproject.toml
+
+    ----- stderr -----
+    warning: `pyproject.toml` does not contain any dependencies (hint: Poetry's format is not supported for now)
+    Resolved 0 packages in [TIME]
+    "###
+    );
+
+    Ok(())
+}
+
 /// Request multiple extras that do not exist as a dependency group in a `pyproject.toml` file.
 #[test]
 fn compile_pyproject_toml_extras_missing() -> Result<()> {