From 0bd4d27e8d9beedbb97bea73b9411a6d88e2aa7d Mon Sep 17 00:00:00 2001
From: Thomas Coratger <60488569+tcoratger@users.noreply.github.com>
Date: Tue, 14 Mar 2023 23:26:48 +0100
Subject: [PATCH] Modify reject algorithm for identical elements (#8446)

# Description

The correction made here concerns the issue #8431. Indeed, the algorithm
initially proposed to remove elements of a `vector` performed a loop
with `remove` and an incident therefore appeared when several values
were equal because the deletion was done outside the length of the
vector:
```rust
let mut found = false;
for (i, col) in cols.clone().iter().enumerate() {
    if col == col_name {
        cols.remove(i);
        vals.remove(i);
        found = true;
    }
}

```

Then, `[[a, a]; [1, 2]] | reject a: ` gave `thread 'main' panicked at
'removal index (is 1) should be < len (is 1)',
crates/nu-protocol/src/value/mod.rs:1213:54`.

The proposed correction is therefore the implementation of the
`retain_mut` utility dedicated to this functionality.

```rust
let mut found = false;
let mut index = 0;
cols.retain_mut(|col| {
    if col == col_name {
        found = true;
        vals.remove(index);
        false
    } else {
        index += 1;
        true
    }
});
```
---
 crates/nu-command/tests/commands/reject.rs | 29 ++++++++++++++++++++++
 crates/nu-protocol/src/value/mod.rs        | 12 ++++++---
 2 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/crates/nu-command/tests/commands/reject.rs b/crates/nu-command/tests/commands/reject.rs
index 7d9d072e5..f9dd15c85 100644
--- a/crates/nu-command/tests/commands/reject.rs
+++ b/crates/nu-command/tests/commands/reject.rs
@@ -118,3 +118,32 @@ fn reject_nested_field() {
 
     assert_eq!(actual.out, "{a: {c: 5}}");
 }
+
+#[test]
+fn reject_two_identical_elements() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+            r#"[[a, a]; [1, 2]] | reject a"#
+        )
+    );
+    assert!(actual.out.contains("record 0 fields"));
+}
+
+#[test]
+fn reject_large_vec_with_two_identical_elements() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+            r#"[[a, b, c, d, e, a]; [1323, 23, 45, 100, 2, 2423]] | reject a"#
+        )
+    );
+    assert!(!actual.out.contains("1323"));
+    assert!(!actual.out.contains("2423"));
+    assert!(actual.out.contains('b'));
+    assert!(actual.out.contains('c'));
+    assert!(actual.out.contains('d'));
+    assert!(actual.out.contains('e'));
+    assert!(actual.out.contains("23"));
+    assert!(actual.out.contains("45"));
+    assert!(actual.out.contains("100"));
+    assert!(actual.out.contains('2'));
+}
diff --git a/crates/nu-protocol/src/value/mod.rs b/crates/nu-protocol/src/value/mod.rs
index c0c00a324..ebc44a2a7 100644
--- a/crates/nu-protocol/src/value/mod.rs
+++ b/crates/nu-protocol/src/value/mod.rs
@@ -1231,13 +1231,17 @@ impl Value {
                                         span: v_span,
                                     } => {
                                         let mut found = false;
-                                        for (i, col) in cols.clone().iter().enumerate() {
+                                        let mut index = 0;
+                                        cols.retain_mut(|col| {
                                             if col == col_name {
-                                                cols.remove(i);
-                                                vals.remove(i);
                                                 found = true;
+                                                vals.remove(index);
+                                                false
+                                            } else {
+                                                index += 1;
+                                                true
                                             }
-                                        }
+                                        });
                                         if !found {
                                             return Err(ShellError::CantFindColumn {
                                                 col_name: col_name.to_string(),