feat(where): Support closures stored in variables

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)
+                    ],
+                )),
+            },
         ]
     }
 }

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]"#)
+}

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();