run-external spreads command if it's a list (#15776)

crates/nu-command/src/system/run_external.rs

@@ -53,9 +53,9 @@ impl Command for External {
     ) -> Result<PipelineData, ShellError> {
         let cwd = engine_state.cwd(Some(stack))?;
         let rest = call.rest::<Value>(engine_state, stack, 0)?;
-        let name_args = rest.split_first();
+        let name_args = rest.split_first().map(|(x, y)| (x, y.to_vec()));
 
-        let Some((name, call_args)) = name_args else {
+        let Some((name, mut call_args)) = name_args else {
             return Err(ShellError::MissingParameter {
                 param_name: "no command given".into(),
                 span: call.head,
@@ -65,6 +65,17 @@ impl Command for External {
         let name_str: Cow<str> = match &name {
             Value::Glob { val, .. } => Cow::Borrowed(val),
             Value::String { val, .. } => Cow::Borrowed(val),
+            Value::List { vals, .. } => {
+                let Some((first, args)) = vals.split_first() else {
+                    return Err(ShellError::MissingParameter {
+                        param_name: "external command given as list empty".into(),
+                        span: call.head,
+                    });
+                };
+                // Prepend elements in command list to the list of arguments except the first
+                call_args.splice(0..0, args.to_vec());
+                first.coerce_str()?
+            }
             _ => Cow::Owned(name.clone().coerce_into_string()?),
         };
 
@@ -164,7 +175,7 @@ impl Command for External {
         command.envs(envs);
 
         // Configure args.
-        let args = eval_external_arguments(engine_state, stack, call_args.to_vec())?;
+        let args = eval_external_arguments(engine_state, stack, call_args)?;
         #[cfg(windows)]
         if is_cmd_internal_command(&name_str) || pathext_script_in_windows {
             // The /D flag disables execution of AutoRun commands from registry.

crates/nu-command/tests/commands/run_external.rs

@@ -535,3 +535,32 @@ fn can_run_ps1_files(prefix: &str) {
         assert!(actual.out.contains("Hello World"));
     });
 }
+
+#[rstest]
+#[case("^")]
+#[case("run-external ")]
+fn expand_command_if_list(#[case] prefix: &str) {
+    use nu_test_support::fs::Stub::FileWithContent;
+    Playground::setup("expand command if list", |dirs, sandbox| {
+        sandbox.with_files(&[FileWithContent("foo.txt", "Hello World")]);
+        let actual = nu!(
+            cwd: dirs.test(),
+            r#"
+                let cmd = [nu `--testbin`]; {}$cmd meow foo.txt
+            "#,
+            prefix
+        );
+
+        assert!(actual.out.contains("Hello World"));
+    })
+}
+
+#[rstest]
+#[case("^")]
+#[case("run-external ")]
+fn error_when_command_list_empty(#[case] prefix: &str) {
+    Playground::setup("error when command is list with no items", |dirs, _| {
+        let actual = nu!(cwd: dirs.test(), "let cmd = []; {}$cmd", prefix);
+        assert!(actual.err.contains("missing parameter"));
+    })
+}