From a70867ed3451a2779be5bb90f7f49b76094f1e60 Mon Sep 17 00:00:00 2001
From: Bahex <17417311+Bahex@users.noreply.github.com>
Date: Mon, 5 May 2025 21:36:44 +0300
Subject: [PATCH 1/3] feat(where): Support closures stored in variables

---
 crates/nu-command/src/filters/where_.rs    | 26 ++++++++++++++++++----
 crates/nu-command/tests/commands/where_.rs | 13 +++++++++++
 crates/nu-parser/src/parser.rs             | 10 +++++++++
 3 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/crates/nu-command/src/filters/where_.rs b/crates/nu-command/src/filters/where_.rs
index cf40639172..2506c90e50 100644
--- a/crates/nu-command/src/filters/where_.rs
+++ b/crates/nu-command/src/filters/where_.rs
@@ -35,7 +35,10 @@ not supported."#
             ])
             .required(
                 "row_condition",
-                SyntaxShape::RowCondition,
+                SyntaxShape::OneOf(vec![
+                    SyntaxShape::RowCondition,
+                    SyntaxShape::Closure(Some(vec![SyntaxShape::Any])),
+                ]),
                 "Filter condition.",
             )
             .allow_variants_without_examples(true)
@@ -125,9 +128,24 @@ not supported."#
                 description: "same as above but with regex only",
                 example: "ls | where name =~ '(?i)readme'",
                 result: None,
-            }
-
-
+            },
+            Example {
+                description: "Filter rows of a table according to a stored condition",
+                example: "let cond = {|x| $x.a > 1}; [{a: 1} {a: 2}] | where $cond",
+                result: Some(Value::test_list(vec![Value::test_record(record! {
+                    "a" => Value::test_int(2),
+                })])),
+            },
+            Example {
+                description: "List all numbers above 3, using an existing closure condition",
+                example: "let a = {$in > 3}; [1, 2, 5, 6] | where $a",
+                result: Some(Value::test_list(
+                    vec![
+                        Value::test_int(5),
+                        Value::test_int(6)
+                    ],
+                )),
+            },
         ]
     }
 }
diff --git a/crates/nu-command/tests/commands/where_.rs b/crates/nu-command/tests/commands/where_.rs
index 7c1fa37f23..837b715c3f 100644
--- a/crates/nu-command/tests/commands/where_.rs
+++ b/crates/nu-command/tests/commands/where_.rs
@@ -209,3 +209,16 @@ fn has_operator() {
     let actual = nu!(r#"{foo: 1} has bar "#);
     assert_eq!(actual.out, "false");
 }
+
+#[test]
+fn stored_condition() {
+    let actual = nu!(r#"let cond = { $in mod 2 == 0 }; 1..10 | where $cond | to nuon"#);
+    assert_eq!(actual.out, r#"[2, 4, 6, 8, 10]"#)
+}
+
+#[test]
+fn nested_stored_condition() {
+    let actual =
+        nu!(r#"let nested = {cond: { $in mod 2 == 0 }}; 1..10 | where $nested.cond | to nuon"#);
+    assert_eq!(actual.out, r#"[2, 4, 6, 8, 10]"#)
+}
diff --git a/crates/nu-parser/src/parser.rs b/crates/nu-parser/src/parser.rs
index 06a38afe7e..3f9d51fb68 100644
--- a/crates/nu-parser/src/parser.rs
+++ b/crates/nu-parser/src/parser.rs
@@ -3613,6 +3613,16 @@ pub fn parse_row_condition(working_set: &mut StateWorkingSet, spans: &[Span]) ->
     let block_id = match expression.expr {
         Expr::Block(block_id) => block_id,
         Expr::Closure(block_id) => block_id,
+        Expr::FullCellPath(ref box_fcp) if box_fcp.head.as_var() != Some(var_id) => {
+            let mut expression = expression;
+            expression.ty = Type::Any;
+            return expression;
+        }
+        Expr::Var(arg_var_id) if arg_var_id != var_id => {
+            let mut expression = expression;
+            expression.ty = Type::Any;
+            return expression;
+        }
         _ => {
             // We have an expression, so let's convert this into a block.
             let mut block = Block::new();

From ac36b4a24757b942cbdf666d4e4cbb21f614a9d0 Mon Sep 17 00:00:00 2001
From: Bahex <17417311+Bahex@users.noreply.github.com>
Date: Tue, 6 May 2025 11:27:34 +0300
Subject: [PATCH 2/3] fix: Further limit expressions that are accepted as a
 closure

- Only variables and cell-path accesses on variables are allowed as
  closures. These can't be `$it` or a path on `$it`
- Any other expression falls back to the usual RowCondition expression
---
 crates/nu-parser/src/parser.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crates/nu-parser/src/parser.rs b/crates/nu-parser/src/parser.rs
index 3f9d51fb68..71510466b6 100644
--- a/crates/nu-parser/src/parser.rs
+++ b/crates/nu-parser/src/parser.rs
@@ -3613,7 +3613,7 @@ pub fn parse_row_condition(working_set: &mut StateWorkingSet, spans: &[Span]) ->
     let block_id = match expression.expr {
         Expr::Block(block_id) => block_id,
         Expr::Closure(block_id) => block_id,
-        Expr::FullCellPath(ref box_fcp) if box_fcp.head.as_var() != Some(var_id) => {
+        Expr::FullCellPath(ref box_fcp) if box_fcp.head.as_var().is_some_and(|id| id != var_id) => {
             let mut expression = expression;
             expression.ty = Type::Any;
             return expression;

From 50e360d898d12cd7c00274f18130e410da5ab1ce Mon Sep 17 00:00:00 2001
From: Bahex <17417311+Bahex@users.noreply.github.com>
Date: Tue, 6 May 2025 12:11:46 +0300
Subject: [PATCH 3/3] test(where): test for possible regression after closure
 support

---
 crates/nu-command/tests/commands/where_.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/crates/nu-command/tests/commands/where_.rs b/crates/nu-command/tests/commands/where_.rs
index 837b715c3f..6ce540635a 100644
--- a/crates/nu-command/tests/commands/where_.rs
+++ b/crates/nu-command/tests/commands/where_.rs
@@ -28,6 +28,12 @@ fn where_inside_block_works() {
     assert_eq!(actual.out, "closure");
 }
 
+#[test]
+fn it_inside_complex_subexpression() {
+    let actual = nu!(r#"1..10 | where [($it * $it)].0 > 40  | to nuon"#);
+    assert_eq!(actual.out, r#"[7, 8, 9, 10]"#)
+}
+
 #[test]
 fn filters_with_0_arity_block() {
     let actual = nu!("[1 2 3 4] | where {|| $in < 3 } | to nuon");