From 808e523adc144197e1145353db4f569bb5613393 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakub=20=C5=BD=C3=A1dn=C3=ADk?= <kubouch@gmail.com>
Date: Sun, 12 Mar 2023 19:16:26 +0200
Subject: [PATCH] Disable alias recursion (#8397)

# Description

Prevents alias from aliasing itself. It allows a commonly requested
pattern similar to `alias ls = ls -l`.

One small issue is that the syntax highlighting is a bit off:

![alias_itself_no_color](https://user-images.githubusercontent.com/25571562/224545129-8a3ff535-347b-4a4e-b686-11493bb2a33b.png)

Fixes https://github.com/nushell/nushell/issues/8246

# User-Facing Changes

Shouldn't be a breaking change.

# Tests + Formatting

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

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

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `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.
---
 crates/nu-command/tests/commands/alias.rs | 20 ++++++++++++++++++++
 crates/nu-parser/src/parse_keywords.rs    | 15 +++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/crates/nu-command/tests/commands/alias.rs b/crates/nu-command/tests/commands/alias.rs
index 91fb26993..7d9817238 100644
--- a/crates/nu-command/tests/commands/alias.rs
+++ b/crates/nu-command/tests/commands/alias.rs
@@ -90,3 +90,23 @@ fn cant_alias_keyword() {
     ));
     assert!(actual.err.contains("cant_alias_keyword"));
 }
+
+#[test]
+fn alias_wont_recurse() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+            module myspamsymbol {
+                export def myfoosymbol [prefix: string, msg: string] {
+                    $prefix + $msg
+                }
+            };
+            use myspamsymbol myfoosymbol;
+            alias myfoosymbol = myfoosymbol 'hello';
+            myfoosymbol ' world'
+        "#
+    ));
+
+    assert_eq!(actual.out, "hello world");
+    assert!(actual.err.is_empty());
+}
diff --git a/crates/nu-parser/src/parse_keywords.rs b/crates/nu-parser/src/parse_keywords.rs
index fd29da114..62b0e3d42 100644
--- a/crates/nu-parser/src/parse_keywords.rs
+++ b/crates/nu-parser/src/parse_keywords.rs
@@ -804,6 +804,13 @@ pub fn parse_alias(
 
             let replacement_spans = &spans[(split_id + 2)..];
 
+            // Temporarily hide the alias itself to prevent recursion
+            let predecl_id = working_set
+                .delta
+                .last_scope_frame_mut()
+                .predecls
+                .remove(&alias_name);
+
             let (expr, err) = parse_call(
                 working_set,
                 replacement_spans,
@@ -812,6 +819,14 @@ pub fn parse_alias(
                 false, // TODO: Should this be set properly???
             );
 
+            if let Some(id) = predecl_id {
+                working_set
+                    .delta
+                    .last_scope_frame_mut()
+                    .predecls
+                    .insert(alias_name.to_vec(), id);
+            }
+
             if let Some(e) = err {
                 if let ParseError::MissingPositional(..) = e {
                     // ignore missing required positional