From 2b92e3e8a7b55e54da9778444795eb967271cceb Mon Sep 17 00:00:00 2001
From: Eli Flanagan <eli@typedspace.com>
Date: Fri, 21 May 2021 22:19:43 -0400
Subject: [PATCH] port group-by to engine-p (#3458)

* migrate group-by to engine p

Part of #3390.

* consume positional argument correctly
---
 crates/nu-command/src/commands/group_by.rs | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/crates/nu-command/src/commands/group_by.rs b/crates/nu-command/src/commands/group_by.rs
index 5d6d1eb41e..f818dce85f 100644
--- a/crates/nu-command/src/commands/group_by.rs
+++ b/crates/nu-command/src/commands/group_by.rs
@@ -9,11 +9,6 @@ use nu_value_ext::as_string;
 
 pub struct Command;
 
-#[derive(Deserialize)]
-pub struct Arguments {
-    grouper: Option<Value>,
-}
-
 impl WholeStreamCommand for Command {
     fn name(&self) -> &str {
         "group-by"
@@ -131,9 +126,10 @@ enum Grouper {
 pub fn group_by(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let name = args.call_info.name_tag.clone();
     let context = Arc::new(EvaluationContext::from_args(&args));
-    let (Arguments { grouper }, input) = args.process()?;
+    let args = args.evaluate_once()?;
 
-    let values: Vec<Value> = input.collect();
+    let grouper = args.opt(0)?;
+    let values: Vec<Value> = args.input.collect();
     let mut keys: Vec<Result<String, ShellError>> = vec![];
     let mut group_strategy = Grouper::ByColumn(None);