From 96e3a3de685eba15191723e9d0e75ff06b604187 Mon Sep 17 00:00:00 2001
From: David Matos <dmatos2012@users.noreply.github.com>
Date: Mon, 27 Feb 2023 03:14:15 +0100
Subject: [PATCH] Error out when Select gets same row (#8200)
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# Description
Fixes #8145, by disallowing any rows that are duplicated.

```
❯ ls | select 0 0
Error:
  × Select only allows unique rows
   ╭─[entry #1:1:1]
 1 │ ls | select 0 0
   ·               ┬
   ·               ╰── duplicated row
   ╰────

```

# User-Facing Changes


# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- [X] `cargo fmt --all -- --check` to check standard code formatting
(`cargo fmt --all` applies these changes)
- [X] `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- [X] `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

---------

Co-authored-by: Reilly Wood <reilly.wood@icloud.com>
---
 crates/nu-command/src/filters/select.rs    | 22 ++++++++++++++++------
 crates/nu-command/tests/commands/select.rs | 12 ++++++++++++
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/crates/nu-command/src/filters/select.rs b/crates/nu-command/src/filters/select.rs
index 3be756729a..b1a627487b 100644
--- a/crates/nu-command/src/filters/select.rs
+++ b/crates/nu-command/src/filters/select.rs
@@ -5,6 +5,7 @@ use nu_protocol::{
     Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
     PipelineIterator, ShellError, Signature, Span, SyntaxShape, Type, Value,
 };
+use std::collections::HashSet;
 
 #[derive(Clone)]
 pub struct Select;
@@ -98,7 +99,7 @@ fn select(
     input: PipelineData,
     ignore_errors: bool,
 ) -> Result<PipelineData, ShellError> {
-    let mut rows = vec![];
+    let mut unique_rows: HashSet<usize> = HashSet::new();
 
     let mut new_columns = vec![];
 
@@ -118,23 +119,32 @@ fn select(
                         Vec::new(),
                     ));
                 }
-
-                rows.push(*val);
+                if unique_rows.contains(val) {
+                    return Err(ShellError::GenericError(
+                        "Select can't get the same row twice".into(),
+                        "duplicated row index".into(),
+                        Some(*span),
+                        None,
+                        Vec::new(),
+                    ));
+                }
+                unique_rows.insert(*val);
             }
             _ => new_columns.push(column),
         };
     }
     let columns = new_columns;
+    let mut unique_rows: Vec<usize> = unique_rows.into_iter().collect();
 
-    let input = if !rows.is_empty() {
-        rows.sort_unstable();
+    let input = if !unique_rows.is_empty() {
+        unique_rows.sort_unstable();
         // let skip = call.has_flag("skip");
         let metadata = input.metadata();
         let pipeline_iter: PipelineIterator = input.into_iter();
 
         NthIterator {
             input: pipeline_iter,
-            rows,
+            rows: unique_rows,
             skip: false,
             current: 0,
         }
diff --git a/crates/nu-command/tests/commands/select.rs b/crates/nu-command/tests/commands/select.rs
index f13751c8eb..e01eb2a0a3 100644
--- a/crates/nu-command/tests/commands/select.rs
+++ b/crates/nu-command/tests/commands/select.rs
@@ -272,3 +272,15 @@ fn select_failed3() {
     assert!(actual.out.is_empty());
     assert!(actual.err.contains("cannot find column"));
 }
+
+#[test]
+fn select_failed4() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        [{a: 1 b: 10}, {a:2, b:11}] | select 0 0
+        "#
+    ));
+
+    assert!(actual.err.contains("Select can't get the same row twice"));
+}