From 6db5692be4de5c5a0e4b2063389d30e9b99b595d Mon Sep 17 00:00:00 2001
From: Hristo Filaretov <hello@hgf.sh>
Date: Thu, 19 Aug 2021 09:05:36 +0200
Subject: [PATCH] Only allow unaliasing in current scope, add tests (#3936)

* unalias only removes aliases in the current scope

* Add a test and fix previous ones which did not function as expected
---
 crates/nu-engine/src/evaluate/scope.rs    |  2 +-
 tests/shell/pipeline/commands/internal.rs | 39 +++++++++++++++++------
 2 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/crates/nu-engine/src/evaluate/scope.rs b/crates/nu-engine/src/evaluate/scope.rs
index 4b12400903..5da6af9fe7 100644
--- a/crates/nu-engine/src/evaluate/scope.rs
+++ b/crates/nu-engine/src/evaluate/scope.rs
@@ -408,7 +408,7 @@ impl ParserScope for Scope {
     }
 
     fn remove_alias(&self, name: &str) {
-        for frame in self.frames.lock().iter_mut().rev() {
+        if let Some(frame) = self.frames.lock().last_mut() {
             frame.aliases.remove(name);
         }
     }
diff --git a/tests/shell/pipeline/commands/internal.rs b/tests/shell/pipeline/commands/internal.rs
index 1b982f4846..d07c9b36fc 100644
--- a/tests/shell/pipeline/commands/internal.rs
+++ b/tests/shell/pipeline/commands/internal.rs
@@ -1150,23 +1150,44 @@ fn unalias_shadowing() {
     let actual = nu!(
         cwd: ".", pipeline(
         r#"
-        alias ll = ls -l
-        let xyz = { ll -a }
-        unalias ll
-        do $xyz
+        def test-shadowing [] {
+            alias greet = echo hello;
+            let xyz = { greet };
+            unalias greet;
+            do $xyz
+        };
+        test-shadowing
         "#)
     );
+    assert_eq!(actual.out, "hello");
+}
 
-    assert_eq!(actual.out, "");
+#[test]
+fn unalias_does_not_escape_scope() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        def test-alias [] {
+            alias greet = echo hello;
+            (unalias greet);
+            greet
+        };
+        test-alias
+        "#)
+    );
+    assert_eq!(actual.out, "hello");
 }
 
 #[test]
 fn unalias_hides_alias() {
     let actual = nu!(cwd: ".", pipeline(
-        r#"alias ll = ls -l
-        ll
-        unalias ll
-        ll
+        r#"
+        def test-alias [] {
+            alias ll = ls -l;
+            unalias ll;
+            ll
+        };
+        test-alias
         "#)
     );