From 5832823dff8e7286c15d011c7a121921eb277f65 Mon Sep 17 00:00:00 2001
From: zc he <blindfs19@gmail.com>
Date: Fri, 21 Mar 2025 19:35:18 +0800
Subject: [PATCH] fix: flatten of empty closures (#15374)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Closes #15373

# Description

Now `ast -f "{||}"` will return

```
╭─content─┬─────shape─────┬─────span──────╮
│ {||}    │ shape_closure │ ╭───────┬───╮ │
│         │               │ │ start │ 0 │ │
│         │               │ │ end   │ 4 │ │
│         │               │ ╰───────┴───╯ │
╰─────────┴───────────────┴───────────────╯
```

Similar to those of `ast -f "[]"`/`ast -f "{}"`

# User-Facing Changes

# Tests + Formatting

I didn't find the right place to do the test, except for the examples of
`ast` command.

# After Submitting
---
 crates/nu-parser/src/flatten.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/crates/nu-parser/src/flatten.rs b/crates/nu-parser/src/flatten.rs
index 46cf901f9a..c49b1720df 100644
--- a/crates/nu-parser/src/flatten.rs
+++ b/crates/nu-parser/src/flatten.rs
@@ -232,7 +232,8 @@ fn flatten_expression_into(
                     None
                 }
             } else {
-                None
+                // for empty closures
+                Some((outer_span, FlatShape::Closure))
             };
 
             output.extend(flattened);