Disallow multiple pylock.toml files

crates/uv-requirements/src/specification.rs

@@ -254,22 +254,19 @@ impl RequirementsSpecification {
             .iter()
             .any(|source| matches!(source, RequirementsSource::PylockToml(..)))
         {
-            if requirements
+            if requirements.len() > 1 {
-                .iter()
-                .any(|source| !matches!(source, RequirementsSource::PylockToml(..)))
-            {
                 return Err(anyhow::anyhow!(
-                    "Cannot specify additional requirements alongside a `pylock.toml` file",
+                    "Cannot specify additional requirements with a `pylock.toml` file",
                 ));
             }
             if !constraints.is_empty() {
                 return Err(anyhow::anyhow!(
-                    "Cannot specify additional requirements with a `pylock.toml` file"
+                    "Cannot specify constraints with a `pylock.toml` file"
                 ));
             }
             if !overrides.is_empty() {
                 return Err(anyhow::anyhow!(
-                    "Cannot specify constraints with a `pylock.toml` file"
+                    "Cannot specify overrides with a `pylock.toml` file"
                 ));
             }
             if !groups.is_empty() {

crates/uv/tests/it/pip_install.rs

@@ -10730,6 +10730,64 @@ fn change_layout_custom_directory() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn pep_751_reject_additional_requirements() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    context.temp_dir.child("pylock.toml").touch()?;
+    context.temp_dir.child("requirements.txt").touch()?;
+
+    // Disallow `pylock.toml` and `requirements.txt` in a single command.
+    uv_snapshot!(context.filters(), context.pip_install()
+        .arg("--preview")
+        .arg("-r")
+        .arg("pylock.toml")
+        .arg("-r")
+        .arg("requirements.txt"), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Cannot specify additional requirements with a `pylock.toml` file
+    "
+    );
+
+    // Disallow multiple `pylock.toml` files in a single command.
+    uv_snapshot!(context.filters(), context.pip_install()
+        .arg("--preview")
+        .arg("-r")
+        .arg("pylock.toml")
+        .arg("-r")
+        .arg("pylock.toml"), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Cannot specify additional requirements with a `pylock.toml` file
+    "
+    );
+
+    // Disallow `pylock.toml` and a constraint in a single command.
+    uv_snapshot!(context.filters(), context.pip_install()
+        .arg("--preview")
+        .arg("-r")
+        .arg("pylock.toml")
+        .arg("-c")
+        .arg("requirements.txt"), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Cannot specify constraints with a `pylock.toml` file
+    "
+    );
+
+    Ok(())
+}
+
 #[test]
 fn pep_751_install_registry_wheel() -> Result<()> {
     let context = TestContext::new("3.12");